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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<!-- Generated by HsColour, http://code.haskell.org/~malcolm/hscolour/ -->
<title>src/Database/PostgreSQL/Simple.hs</title>
<link type='text/css' rel='stylesheet' href='hscolour.css' />
</head>
<body>
<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE DeriveDataTypeable #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# LANGUAGE NamedFieldPuns #-}</span>
<a name="line-3"></a><span class='hs-comment'>{-# LANGUAGE OverloadedStrings #-}</span>
<a name="line-4"></a><span class='hs-comment'>{-# LANGUAGE PatternGuards #-}</span>
<a name="line-5"></a><span class='hs-comment'>{-# LANGUAGE RecordWildCards #-}</span>
<a name="line-6"></a><span class='hs-comment'>{-# LANGUAGE ViewPatterns #-}</span>
<a name="line-7"></a>
<a name="line-8"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-9"></a><span class='hs-comment'>-- |</span>
<a name="line-10"></a><span class='hs-comment'>-- Module:      Database.PostgreSQL.Simple</span>
<a name="line-11"></a><span class='hs-comment'>-- Copyright:   (c) 2011 MailRank, Inc.</span>
<a name="line-12"></a><span class='hs-comment'>--              (c) 2011-2012 Leon P Smith</span>
<a name="line-13"></a><span class='hs-comment'>-- License:     BSD3</span>
<a name="line-14"></a><span class='hs-comment'>-- Maintainer:  Leon P Smith &lt;leon@melding-monads.com&gt;</span>
<a name="line-15"></a><span class='hs-comment'>-- Stability:   experimental</span>
<a name="line-16"></a><span class='hs-comment'>--</span>
<a name="line-17"></a><span class='hs-comment'>-- A mid-level client library for the PostgreSQL database, aimed at ease of</span>
<a name="line-18"></a><span class='hs-comment'>-- use and high performance.</span>
<a name="line-19"></a><span class='hs-comment'>--</span>
<a name="line-20"></a><span class='hs-comment'>------------------------------------------------------------------------------</span>
<a name="line-21"></a>
<a name="line-22"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span>
<a name="line-23"></a>    <span class='hs-layout'>(</span>
<a name="line-24"></a>    <span class='hs-comment'>-- * Writing queries</span>
<a name="line-25"></a>    <span class='hs-comment'>-- $use</span>
<a name="line-26"></a>
<a name="line-27"></a>    <span class='hs-comment'>-- ** The Query type</span>
<a name="line-28"></a>    <span class='hs-comment'>-- $querytype</span>
<a name="line-29"></a>
<a name="line-30"></a>    <span class='hs-comment'>-- ** Parameter substitution</span>
<a name="line-31"></a>    <span class='hs-comment'>-- $subst</span>
<a name="line-32"></a>
<a name="line-33"></a>    <span class='hs-comment'>-- *** Type inference</span>
<a name="line-34"></a>    <span class='hs-comment'>-- $inference</span>
<a name="line-35"></a>
<a name="line-36"></a>    <span class='hs-comment'>-- ** Substituting a single parameter</span>
<a name="line-37"></a>    <span class='hs-comment'>-- $only_param</span>
<a name="line-38"></a>
<a name="line-39"></a>    <span class='hs-comment'>-- ** Representing a list of values</span>
<a name="line-40"></a>    <span class='hs-comment'>-- $in</span>
<a name="line-41"></a>
<a name="line-42"></a>    <span class='hs-comment'>-- ** Modifying multiple rows at once</span>
<a name="line-43"></a>    <span class='hs-comment'>-- $many</span>
<a name="line-44"></a>
<a name="line-45"></a>    <span class='hs-comment'>-- ** @RETURNING@: modifications that returns results</span>
<a name="line-46"></a>    <span class='hs-comment'>-- $returning</span>
<a name="line-47"></a>
<a name="line-48"></a>    <span class='hs-comment'>-- * Extracting results</span>
<a name="line-49"></a>    <span class='hs-comment'>-- $result</span>
<a name="line-50"></a>
<a name="line-51"></a>    <span class='hs-comment'>-- ** Handling null values</span>
<a name="line-52"></a>    <span class='hs-comment'>-- $null</span>
<a name="line-53"></a>
<a name="line-54"></a>    <span class='hs-comment'>-- ** Type conversions</span>
<a name="line-55"></a>    <span class='hs-comment'>-- $types</span>
<a name="line-56"></a>
<a name="line-57"></a>    <span class='hs-comment'>-- * Types</span>
<a name="line-58"></a>      <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-conid'>ConnectInfo</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-59"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Connection</span>
<a name="line-60"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Query</span>
<a name="line-61"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>ToRow</span>
<a name="line-62"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>FromRow</span>
<a name="line-63"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>In</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-64"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Binary</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-65"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Only</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-66"></a>    <span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conop'>:.</span><span class='hs-layout'>)</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-67"></a>    <span class='hs-comment'>-- ** Exceptions</span>
<a name="line-68"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>SqlError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-69"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>ExecStatus</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-70"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>FormatError</span><span class='hs-layout'>(</span><span class='hs-varid'>fmtMessage</span><span class='hs-layout'>,</span> <span class='hs-varid'>fmtQuery</span><span class='hs-layout'>,</span> <span class='hs-varid'>fmtParams</span><span class='hs-layout'>)</span>
<a name="line-71"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>QueryError</span><span class='hs-layout'>(</span><span class='hs-varid'>qeMessage</span><span class='hs-layout'>,</span> <span class='hs-varid'>qeQuery</span><span class='hs-layout'>)</span>
<a name="line-72"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>ResultError</span><span class='hs-layout'>(</span><span class='hs-varid'>errSQLType</span><span class='hs-layout'>,</span> <span class='hs-varid'>errHaskellType</span><span class='hs-layout'>,</span> <span class='hs-varid'>errMessage</span><span class='hs-layout'>)</span>
<a name="line-73"></a>    <span class='hs-comment'>-- * Connection management</span>
<a name="line-74"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-varid'>connect</span>
<a name="line-75"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-varid'>connectPostgreSQL</span>
<a name="line-76"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-varid'>postgreSQLConnectionString</span>
<a name="line-77"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-varid'>defaultConnectInfo</span>
<a name="line-78"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>Base</span><span class='hs-varop'>.</span><span class='hs-varid'>close</span>
<a name="line-79"></a>    <span class='hs-comment'>-- * Queries that return results</span>
<a name="line-80"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>query</span>
<a name="line-81"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>query_</span>
<a name="line-82"></a>    <span class='hs-comment'>-- ** Queries taking parser as argument</span>
<a name="line-83"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>queryWith</span>
<a name="line-84"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>queryWith_</span>
<a name="line-85"></a>    <span class='hs-comment'>-- * Queries that stream results</span>
<a name="line-86"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>FoldOptions</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-87"></a>    <span class='hs-layout'>,</span> <span class='hs-conid'>FetchQuantity</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span>
<a name="line-88"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>defaultFoldOptions</span>
<a name="line-89"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>fold</span>
<a name="line-90"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>foldWithOptions</span>
<a name="line-91"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>fold_</span>
<a name="line-92"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>foldWithOptions_</span>
<a name="line-93"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>forEach</span>
<a name="line-94"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>forEach_</span>
<a name="line-95"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>returning</span>
<a name="line-96"></a>    <span class='hs-comment'>-- * Statements that do not return results</span>
<a name="line-97"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>execute</span>
<a name="line-98"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>execute_</span>
<a name="line-99"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>executeMany</span>
<a name="line-100"></a><span class='hs-comment'>--    , Base.insertID</span>
<a name="line-101"></a>    <span class='hs-comment'>-- * Transaction handling</span>
<a name="line-102"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>withTransaction</span>
<a name="line-103"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>withSavepoint</span>
<a name="line-104"></a><span class='hs-comment'>--    , Base.autocommit</span>
<a name="line-105"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>begin</span>
<a name="line-106"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>commit</span>
<a name="line-107"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>rollback</span>
<a name="line-108"></a>    <span class='hs-comment'>-- * Helper functions</span>
<a name="line-109"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>formatMany</span>
<a name="line-110"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>formatQuery</span>
<a name="line-111"></a>    <span class='hs-layout'>)</span> <span class='hs-keyword'>where</span>
<a name="line-112"></a>
<a name="line-113"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Blaze</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Builder</span>
<a name="line-114"></a>                   <span class='hs-layout'>(</span> <span class='hs-conid'>Builder</span><span class='hs-layout'>,</span> <span class='hs-varid'>fromByteString</span><span class='hs-layout'>,</span> <span class='hs-varid'>toByteString</span> <span class='hs-layout'>)</span>
<a name="line-115"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Blaze</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Builder</span><span class='hs-varop'>.</span><span class='hs-conid'>Char8</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromChar</span><span class='hs-layout'>)</span>
<a name="line-116"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Blaze</span><span class='hs-varop'>.</span><span class='hs-conid'>Text</span> <span class='hs-layout'>(</span> <span class='hs-varid'>integral</span> <span class='hs-layout'>)</span>
<a name="line-117"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Applicative</span> <span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varop'>&lt;$&gt;</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>pure</span><span class='hs-layout'>)</span>
<a name="line-118"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Exception</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>E</span>
<a name="line-119"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span> <span class='hs-layout'>(</span><span class='hs-varid'>foldM</span><span class='hs-layout'>)</span>
<a name="line-120"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span> <span class='hs-layout'>(</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span>
<a name="line-121"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Int</span> <span class='hs-layout'>(</span><span class='hs-conid'>Int64</span><span class='hs-layout'>)</span>
<a name="line-122"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>List</span> <span class='hs-layout'>(</span><span class='hs-varid'>intersperse</span><span class='hs-layout'>)</span>
<a name="line-123"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Monoid</span> <span class='hs-layout'>(</span><span class='hs-varid'>mconcat</span><span class='hs-layout'>)</span>
<a name="line-124"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Typeable</span> <span class='hs-layout'>(</span><span class='hs-conid'>Typeable</span><span class='hs-layout'>)</span>
<a name="line-125"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>Compat</span> <span class='hs-layout'>(</span> <span class='hs-layout'>(</span><span class='hs-varop'>&lt;&gt;</span><span class='hs-layout'>)</span> <span class='hs-layout'>)</span>
<a name="line-126"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>FromField</span> <span class='hs-layout'>(</span><span class='hs-conid'>ResultError</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-127"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>FromRow</span> <span class='hs-layout'>(</span><span class='hs-conid'>FromRow</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-128"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>Ok</span>
<a name="line-129"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>ToField</span> <span class='hs-layout'>(</span><span class='hs-conid'>Action</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>inQuotes</span><span class='hs-layout'>)</span>
<a name="line-130"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>ToRow</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-131"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>Types</span>
<a name="line-132"></a>                   <span class='hs-layout'>(</span> <span class='hs-conid'>Binary</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>In</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Only</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-conid'>Query</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-layout'>(</span><span class='hs-conop'>:.</span><span class='hs-layout'>)</span><span class='hs-layout'>(</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>)</span> <span class='hs-layout'>)</span>
<a name="line-133"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>Internal</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>Base</span>
<a name="line-134"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>Transaction</span>
<a name="line-135"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>Simple</span><span class='hs-varop'>.</span><span class='hs-conid'>TypeInfo</span>
<a name="line-136"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Database</span><span class='hs-varop'>.</span><span class='hs-conid'>PostgreSQL</span><span class='hs-varop'>.</span><span class='hs-conid'>LibPQ</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>PQ</span>
<a name="line-137"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>ByteString</span><span class='hs-varop'>.</span><span class='hs-conid'>Char8</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>B</span>
<a name="line-138"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Text</span>          <span class='hs-keyword'>as</span> <span class='hs-conid'>T</span>
<a name="line-139"></a><span class='hs-keyword'>import</span> <span class='hs-keyword'>qualified</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Text</span><span class='hs-varop'>.</span><span class='hs-conid'>Encoding</span> <span class='hs-keyword'>as</span> <span class='hs-conid'>TE</span>
<a name="line-140"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>Reader</span>
<a name="line-141"></a><span class='hs-keyword'>import</span>           <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span><span class='hs-varop'>.</span><span class='hs-conid'>Trans</span><span class='hs-varop'>.</span><span class='hs-conid'>State</span><span class='hs-varop'>.</span><span class='hs-conid'>Strict</span>
<a name="line-142"></a>
<a name="line-143"></a><a name="FormatError"></a><span class='hs-comment'>-- | Exception thrown if a 'Query' could not be formatted correctly.</span>
<a name="line-144"></a><a name="FormatError"></a><span class='hs-comment'>-- This may occur if the number of \'@?@\' characters in the query</span>
<a name="line-145"></a><a name="FormatError"></a><span class='hs-comment'>-- string does not match the number of parameters provided.</span>
<a name="line-146"></a><a name="FormatError"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>FormatError</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FormatError</span> <span class='hs-layout'>{</span>
<a name="line-147"></a>      <span class='hs-varid'>fmtMessage</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>String</span>
<a name="line-148"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>fmtQuery</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Query</span>
<a name="line-149"></a>    <span class='hs-layout'>,</span> <span class='hs-varid'>fmtParams</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ByteString</span><span class='hs-keyglyph'>]</span>
<a name="line-150"></a>    <span class='hs-layout'>}</span> <span class='hs-keyword'>deriving</span> <span class='hs-layout'>(</span><span class='hs-conid'>Eq</span><span class='hs-layout'>,</span> <span class='hs-conid'>Show</span><span class='hs-layout'>,</span> <span class='hs-conid'>Typeable</span><span class='hs-layout'>)</span>
<a name="line-151"></a>
<a name="line-152"></a><a name="instance%20Connection%20-%3e%20Query%20-%3e%20q%20-%3e%20IO%20ByteString%20formatQuery%20conn%20q@(Query%20template)%20qs%20%7c%20null%20xs%20&&%20'?'%20%60B.notElem%60%20template%20=%20return%20template%20%7c%20otherwise%20=%20toByteString%20%3c$%3e%20buildQuery%20conn%20q%20template%20xs"></a><span class='hs-keyword'>instance</span> <span class='hs-conid'>Exception</span> <span class='hs-conid'>FormatError</span>
<a name="line-153"></a>
<a name="line-154"></a><a name="formatQuery"></a><span class='hs-comment'>-- | Format a query string.</span>
<a name="line-155"></a><span class='hs-comment'>--</span>
<a name="line-156"></a><span class='hs-comment'>-- This function is exposed to help with debugging and logging. Do not</span>
<a name="line-157"></a><span class='hs-comment'>-- use it to prepare queries for execution.</span>
<a name="line-158"></a><span class='hs-comment'>--</span>
<a name="line-159"></a><span class='hs-comment'>-- String parameters are escaped according to the character set in use</span>
<a name="line-160"></a><span class='hs-comment'>-- on the 'Connection'.</span>
<a name="line-161"></a><span class='hs-comment'>--</span>
<a name="line-162"></a><span class='hs-comment'>-- Throws 'FormatError' if the query string could not be formatted</span>
<a name="line-163"></a><span class='hs-comment'>-- correctly.</span>
<a name="line-164"></a><span class='hs-definition'>formatQuery</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>ByteString</span>
<a name="line-165"></a><span class='hs-definition'>formatQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>template</span><span class='hs-layout'>)</span> <span class='hs-varid'>qs</span>
<a name="line-166"></a>    <span class='hs-keyglyph'>|</span> <span class='hs-varid'>null</span> <span class='hs-varid'>xs</span> <span class='hs-varop'>&amp;&amp;</span> <span class='hs-chr'>'?'</span> <span class='hs-varop'>`</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>notElem</span><span class='hs-varop'>`</span> <span class='hs-varid'>template</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-varid'>template</span>
<a name="line-167"></a>    <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toByteString</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-varid'>buildQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>template</span> <span class='hs-varid'>xs</span>
<a name="line-168"></a>  <span class='hs-keyword'>where</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toRow</span> <span class='hs-varid'>qs</span>
<a name="line-169"></a>
<a name="line-170"></a><a name="formatMany"></a><span class='hs-comment'>-- | Format a query string with a variable number of rows.</span>
<a name="line-171"></a><span class='hs-comment'>--</span>
<a name="line-172"></a><span class='hs-comment'>-- This function is exposed to help with debugging and logging. Do not</span>
<a name="line-173"></a><span class='hs-comment'>-- use it to prepare queries for execution.</span>
<a name="line-174"></a><span class='hs-comment'>--</span>
<a name="line-175"></a><span class='hs-comment'>-- The query string must contain exactly one substitution group,</span>
<a name="line-176"></a><span class='hs-comment'>-- identified by the SQL keyword \"@VALUES@\" (case insensitive)</span>
<a name="line-177"></a><span class='hs-comment'>-- followed by an \"@(@\" character, a series of one or more \"@?@\"</span>
<a name="line-178"></a><span class='hs-comment'>-- characters separated by commas, and a \"@)@\" character. White</span>
<a name="line-179"></a><span class='hs-comment'>-- space in a substitution group is permitted.</span>
<a name="line-180"></a><span class='hs-comment'>--</span>
<a name="line-181"></a><span class='hs-comment'>-- Throws 'FormatError' if the query string could not be formatted</span>
<a name="line-182"></a><span class='hs-comment'>-- correctly.</span>
<a name="line-183"></a><span class='hs-definition'>formatMany</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>q</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>ByteString</span>
<a name="line-184"></a><span class='hs-definition'>formatMany</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>q</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmtError</span> <span class='hs-str'>"no rows supplied"</span> <span class='hs-varid'>q</span> <span class='hs-conid'>[]</span>
<a name="line-185"></a><span class='hs-definition'>formatMany</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>template</span><span class='hs-layout'>)</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-186"></a>  <span class='hs-keyword'>case</span> <span class='hs-varid'>parseTemplate</span> <span class='hs-varid'>template</span> <span class='hs-keyword'>of</span>
<a name="line-187"></a>    <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-varid'>before</span><span class='hs-layout'>,</span> <span class='hs-varid'>qbits</span><span class='hs-layout'>,</span> <span class='hs-varid'>after</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-188"></a>      <span class='hs-varid'>bs</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>mapM</span> <span class='hs-layout'>(</span><span class='hs-varid'>buildQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>qbits</span> <span class='hs-varop'>.</span> <span class='hs-varid'>toRow</span><span class='hs-layout'>)</span> <span class='hs-varid'>qs</span>
<a name="line-189"></a>      <span class='hs-varid'>return</span> <span class='hs-varop'>.</span> <span class='hs-varid'>toByteString</span> <span class='hs-varop'>.</span> <span class='hs-varid'>mconcat</span> <span class='hs-varop'>$</span> <span class='hs-varid'>fromByteString</span> <span class='hs-varid'>before</span> <span class='hs-conop'>:</span>
<a name="line-190"></a>                                        <span class='hs-varid'>intersperse</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromChar</span> <span class='hs-chr'>','</span><span class='hs-layout'>)</span> <span class='hs-varid'>bs</span> <span class='hs-varop'>++</span>
<a name="line-191"></a>                                        <span class='hs-keyglyph'>[</span><span class='hs-varid'>fromByteString</span> <span class='hs-varid'>after</span><span class='hs-keyglyph'>]</span>
<a name="line-192"></a>    <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>fmtError</span> <span class='hs-str'>"syntax error in multi-row template"</span> <span class='hs-varid'>q</span> <span class='hs-conid'>[]</span>
<a name="line-193"></a>
<a name="line-194"></a><a name="parseTemplate"></a><span class='hs-comment'>-- Split the input string into three pieces, @before@, @qbits@, and @after@,</span>
<a name="line-195"></a><span class='hs-comment'>-- following this grammar:</span>
<a name="line-196"></a><span class='hs-comment'>--</span>
<a name="line-197"></a><span class='hs-comment'>-- start: ^ before qbits after $</span>
<a name="line-198"></a><span class='hs-comment'>--     before: ([^?]* [^?\w])? 'VALUES' \s*</span>
<a name="line-199"></a><span class='hs-comment'>--     qbits:  '(' \s* '?' \s* (',' \s* '?' \s*)* ')'</span>
<a name="line-200"></a><span class='hs-comment'>--     after:  [^?]*</span>
<a name="line-201"></a><span class='hs-comment'>--</span>
<a name="line-202"></a><span class='hs-comment'>-- \s: [ \t\n\r\f]</span>
<a name="line-203"></a><span class='hs-comment'>-- \w: [A-Z] | [a-z] | [\x80-\xFF] | '_' | '$' | [0-9]</span>
<a name="line-204"></a><span class='hs-comment'>--</span>
<a name="line-205"></a><span class='hs-comment'>-- This would be much more concise with some sort of regex engine.</span>
<a name="line-206"></a><span class='hs-comment'>-- 'formatMany' used to use pcre-light instead of this hand-written parser,</span>
<a name="line-207"></a><span class='hs-comment'>-- but pcre is a hassle to install on Windows.</span>
<a name="line-208"></a><span class='hs-definition'>parseTemplate</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>ByteString</span><span class='hs-layout'>,</span> <span class='hs-conid'>ByteString</span><span class='hs-layout'>,</span> <span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span>
<a name="line-209"></a><span class='hs-definition'>parseTemplate</span> <span class='hs-varid'>template</span> <span class='hs-keyglyph'>=</span>
<a name="line-210"></a>    <span class='hs-comment'>-- Convert input string to uppercase, to facilitate searching.</span>
<a name="line-211"></a>    <span class='hs-varid'>search</span> <span class='hs-varop'>$</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>map</span> <span class='hs-varid'>toUpper_ascii</span> <span class='hs-varid'>template</span>
<a name="line-212"></a>  <span class='hs-keyword'>where</span>
<a name="line-213"></a>    <span class='hs-comment'>-- Search for the next occurrence of "VALUES"</span>
<a name="line-214"></a>    <span class='hs-varid'>search</span> <span class='hs-varid'>bs</span> <span class='hs-keyglyph'>=</span>
<a name="line-215"></a>        <span class='hs-keyword'>case</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>breakSubstring</span> <span class='hs-str'>"VALUES"</span> <span class='hs-varid'>bs</span> <span class='hs-keyword'>of</span>
<a name="line-216"></a>            <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span>
<a name="line-217"></a>                <span class='hs-comment'>-- If "VALUES" is not present in the string, or any '?' characters</span>
<a name="line-218"></a>                <span class='hs-comment'>-- were encountered prior to it, fail.</span>
<a name="line-219"></a>                <span class='hs-keyglyph'>|</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>null</span> <span class='hs-varid'>y</span> <span class='hs-varop'>||</span> <span class='hs-layout'>(</span><span class='hs-chr'>'?'</span> <span class='hs-varop'>`</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>elem</span><span class='hs-varop'>`</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-220"></a>               <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Nothing</span>
<a name="line-221"></a>
<a name="line-222"></a>                <span class='hs-comment'>-- If "VALUES" is preceded by an identifier character (a.k.a. \w),</span>
<a name="line-223"></a>                <span class='hs-comment'>-- try the next occurrence.</span>
<a name="line-224"></a>                <span class='hs-keyglyph'>|</span> <span class='hs-varid'>not</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>null</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>isIdent</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>last</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-225"></a>               <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>search</span> <span class='hs-varop'>$</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>drop</span> <span class='hs-num'>6</span> <span class='hs-varid'>y</span>
<a name="line-226"></a>
<a name="line-227"></a>                <span class='hs-comment'>-- Otherwise, we have a legitimate "VALUES" token.</span>
<a name="line-228"></a>                <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span>
<a name="line-229"></a>               <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>parseQueryBits</span> <span class='hs-varop'>$</span> <span class='hs-varid'>skipSpace</span> <span class='hs-varop'>$</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>drop</span> <span class='hs-num'>6</span> <span class='hs-varid'>y</span>
<a name="line-230"></a>
<a name="line-231"></a>    <span class='hs-comment'>-- Parse '(' \s* '?' \s* .  If this doesn't match</span>
<a name="line-232"></a>    <span class='hs-comment'>-- (and we don't consume a '?'), look for another "VALUES".</span>
<a name="line-233"></a>    <span class='hs-comment'>--</span>
<a name="line-234"></a>    <span class='hs-comment'>-- qb points to the open paren (if present), meaning it points to the</span>
<a name="line-235"></a>    <span class='hs-comment'>-- beginning of the "qbits" production described above.  This is why we</span>
<a name="line-236"></a>    <span class='hs-comment'>-- pass it down to finishQueryBits.</span>
<a name="line-237"></a>    <span class='hs-varid'>parseQueryBits</span> <span class='hs-varid'>qb</span>
<a name="line-238"></a>        <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-chr'>'('</span><span class='hs-layout'>,</span> <span class='hs-varid'>skipSpace</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>bs1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>uncons</span> <span class='hs-varid'>qb</span>
<a name="line-239"></a>        <span class='hs-layout'>,</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-chr'>'?'</span><span class='hs-layout'>,</span> <span class='hs-varid'>skipSpace</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>bs2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>uncons</span> <span class='hs-varid'>bs1</span>
<a name="line-240"></a>        <span class='hs-keyglyph'>=</span> <span class='hs-varid'>finishQueryBits</span> <span class='hs-varid'>qb</span> <span class='hs-varid'>bs2</span>
<a name="line-241"></a>        <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span>
<a name="line-242"></a>        <span class='hs-keyglyph'>=</span> <span class='hs-varid'>search</span> <span class='hs-varid'>qb</span>
<a name="line-243"></a>
<a name="line-244"></a>    <span class='hs-comment'>-- Parse (',' \s* '?' \s*)* ')' [^?]* .</span>
<a name="line-245"></a>    <span class='hs-comment'>--</span>
<a name="line-246"></a>    <span class='hs-comment'>-- Since we've already consumed at least one '?', there's no turning back.</span>
<a name="line-247"></a>    <span class='hs-comment'>-- The parse has to succeed here, or the whole thing fails</span>
<a name="line-248"></a>    <span class='hs-comment'>-- (because we don't allow '?' to appear outside of the VALUES list).</span>
<a name="line-249"></a>    <span class='hs-varid'>finishQueryBits</span> <span class='hs-varid'>qb</span> <span class='hs-varid'>bs0</span>
<a name="line-250"></a>        <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-chr'>')'</span><span class='hs-layout'>,</span> <span class='hs-varid'>bs1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>uncons</span> <span class='hs-varid'>bs0</span>
<a name="line-251"></a>        <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>if</span> <span class='hs-chr'>'?'</span> <span class='hs-varop'>`</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>elem</span><span class='hs-varop'>`</span> <span class='hs-varid'>bs1</span>
<a name="line-252"></a>              <span class='hs-keyword'>then</span> <span class='hs-conid'>Nothing</span>
<a name="line-253"></a>              <span class='hs-keyword'>else</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>slice3</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qb</span> <span class='hs-varid'>bs1</span>
<a name="line-254"></a>        <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-chr'>','</span><span class='hs-layout'>,</span> <span class='hs-varid'>skipSpace</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>bs1</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>uncons</span> <span class='hs-varid'>bs0</span>
<a name="line-255"></a>        <span class='hs-layout'>,</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-chr'>'?'</span><span class='hs-layout'>,</span> <span class='hs-varid'>skipSpace</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>bs2</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>uncons</span> <span class='hs-varid'>bs1</span>
<a name="line-256"></a>        <span class='hs-keyglyph'>=</span> <span class='hs-varid'>finishQueryBits</span> <span class='hs-varid'>qb</span> <span class='hs-varid'>bs2</span>
<a name="line-257"></a>        <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span>
<a name="line-258"></a>        <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-259"></a>
<a name="line-260"></a>    <span class='hs-comment'>-- Slice a string into three pieces, given the start offset of the second</span>
<a name="line-261"></a>    <span class='hs-comment'>-- and third pieces.  Each "offset" is actually a tail of the uppercase</span>
<a name="line-262"></a>    <span class='hs-comment'>-- version of the template string.  Its length is used to infer the offset.</span>
<a name="line-263"></a>    <span class='hs-comment'>--</span>
<a name="line-264"></a>    <span class='hs-comment'>-- It is important to note that we only slice the original template.</span>
<a name="line-265"></a>    <span class='hs-comment'>-- We don't want our all-caps trick messing up the actual query string.</span>
<a name="line-266"></a>    <span class='hs-varid'>slice3</span> <span class='hs-varid'>source</span> <span class='hs-varid'>p1</span> <span class='hs-varid'>p2</span> <span class='hs-keyglyph'>=</span>
<a name="line-267"></a>        <span class='hs-layout'>(</span><span class='hs-varid'>s1</span><span class='hs-layout'>,</span> <span class='hs-varid'>s2</span><span class='hs-layout'>,</span> <span class='hs-varid'>source''</span><span class='hs-layout'>)</span>
<a name="line-268"></a>      <span class='hs-keyword'>where</span>
<a name="line-269"></a>        <span class='hs-layout'>(</span><span class='hs-varid'>s1</span><span class='hs-layout'>,</span> <span class='hs-varid'>source'</span><span class='hs-layout'>)</span>  <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>splitAt</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>source</span> <span class='hs-comment'>-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>p1</span><span class='hs-layout'>)</span> <span class='hs-varid'>source</span>
<a name="line-270"></a>        <span class='hs-layout'>(</span><span class='hs-varid'>s2</span><span class='hs-layout'>,</span> <span class='hs-varid'>source''</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>splitAt</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>p1</span>     <span class='hs-comment'>-</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>p2</span><span class='hs-layout'>)</span> <span class='hs-varid'>source'</span>
<a name="line-271"></a>
<a name="line-272"></a>    <span class='hs-varid'>toUpper_ascii</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&gt;=</span> <span class='hs-chr'>'a'</span> <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&lt;=</span> <span class='hs-chr'>'z'</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toEnum</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromEnum</span> <span class='hs-varid'>c</span> <span class='hs-comment'>-</span> <span class='hs-num'>32</span><span class='hs-layout'>)</span>
<a name="line-273"></a>                    <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span>            <span class='hs-keyglyph'>=</span> <span class='hs-varid'>c</span>
<a name="line-274"></a>
<a name="line-275"></a>    <span class='hs-comment'>-- Based on the definition of {ident_cont} in src/backend/parser/scan.l</span>
<a name="line-276"></a>    <span class='hs-comment'>-- in the PostgreSQL source.  No need to check [a-z], since we converted</span>
<a name="line-277"></a>    <span class='hs-comment'>-- the whole string to uppercase.</span>
<a name="line-278"></a>    <span class='hs-varid'>isIdent</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varop'>&gt;=</span> <span class='hs-chr'>'0'</span>    <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&lt;=</span> <span class='hs-chr'>'9'</span><span class='hs-layout'>)</span>
<a name="line-279"></a>             <span class='hs-varop'>||</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varop'>&gt;=</span> <span class='hs-chr'>'A'</span>    <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&lt;=</span> <span class='hs-chr'>'Z'</span><span class='hs-layout'>)</span>
<a name="line-280"></a>             <span class='hs-varop'>||</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varop'>&gt;=</span> <span class='hs-chr'>'\x80'</span> <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&lt;=</span> <span class='hs-chr'>'\xFF'</span><span class='hs-layout'>)</span>
<a name="line-281"></a>             <span class='hs-varop'>||</span> <span class='hs-varid'>c</span> <span class='hs-varop'>==</span> <span class='hs-chr'>'_'</span>
<a name="line-282"></a>             <span class='hs-varop'>||</span> <span class='hs-varid'>c</span> <span class='hs-varop'>==</span> <span class='hs-chr'>'$'</span>
<a name="line-283"></a>
<a name="line-284"></a>    <span class='hs-comment'>-- Based on {space} in scan.l</span>
<a name="line-285"></a>    <span class='hs-varid'>isSpace_ascii</span> <span class='hs-varid'>c</span> <span class='hs-keyglyph'>=</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varop'>==</span> <span class='hs-chr'>' '</span><span class='hs-layout'>)</span> <span class='hs-varop'>||</span> <span class='hs-layout'>(</span><span class='hs-varid'>c</span> <span class='hs-varop'>&gt;=</span> <span class='hs-chr'>'\t'</span> <span class='hs-varop'>&amp;&amp;</span> <span class='hs-varid'>c</span> <span class='hs-varop'>&lt;=</span> <span class='hs-chr'>'\r'</span><span class='hs-layout'>)</span>
<a name="line-286"></a>
<a name="line-287"></a>    <span class='hs-varid'>skipSpace</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>dropWhile</span> <span class='hs-varid'>isSpace_ascii</span>
<a name="line-288"></a>
<a name="line-289"></a><a name="escapeStringConn"></a><span class='hs-definition'>escapeStringConn</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>ByteString</span> <span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span>
<a name="line-290"></a><span class='hs-definition'>escapeStringConn</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span>
<a name="line-291"></a>    <span class='hs-varid'>withConnection</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>c</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-292"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>escapeStringConn</span> <span class='hs-varid'>c</span> <span class='hs-varid'>s</span> <span class='hs-varop'>&gt;&gt;=</span> <span class='hs-varid'>checkError</span> <span class='hs-varid'>c</span>
<a name="line-293"></a>
<a name="line-294"></a><a name="escapeByteaConn"></a><span class='hs-definition'>escapeByteaConn</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>ByteString</span> <span class='hs-conid'>ByteString</span><span class='hs-layout'>)</span>
<a name="line-295"></a><span class='hs-definition'>escapeByteaConn</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span>
<a name="line-296"></a>    <span class='hs-varid'>withConnection</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>c</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-297"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>escapeByteaConn</span> <span class='hs-varid'>c</span> <span class='hs-varid'>s</span> <span class='hs-varop'>&gt;&gt;=</span> <span class='hs-varid'>checkError</span> <span class='hs-varid'>c</span>
<a name="line-298"></a>
<a name="line-299"></a><a name="checkError"></a><span class='hs-definition'>checkError</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Maybe</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-layout'>(</span><span class='hs-conid'>Either</span> <span class='hs-conid'>ByteString</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-300"></a><span class='hs-definition'>checkError</span> <span class='hs-keyword'>_</span> <span class='hs-layout'>(</span><span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-varop'>$</span> <span class='hs-conid'>Right</span> <span class='hs-varid'>x</span>
<a name="line-301"></a><span class='hs-definition'>checkError</span> <span class='hs-varid'>c</span> <span class='hs-conid'>Nothing</span>  <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Left</span> <span class='hs-varop'>.</span> <span class='hs-varid'>maybe</span> <span class='hs-str'>""</span> <span class='hs-varid'>id</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>errorMessage</span> <span class='hs-varid'>c</span>
<a name="line-302"></a>
<a name="line-303"></a><a name="buildQuery"></a><span class='hs-definition'>buildQuery</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Action</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>Builder</span>
<a name="line-304"></a><span class='hs-definition'>buildQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>template</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>zipParams</span> <span class='hs-layout'>(</span><span class='hs-varid'>split</span> <span class='hs-varid'>template</span><span class='hs-layout'>)</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-varid'>mapM</span> <span class='hs-varid'>sub</span> <span class='hs-varid'>xs</span>
<a name="line-305"></a>  <span class='hs-keyword'>where</span> <span class='hs-varid'>quote</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>either</span> <span class='hs-layout'>(</span><span class='hs-keyglyph'>\</span><span class='hs-varid'>msg</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>fmtError</span> <span class='hs-layout'>(</span><span class='hs-varid'>utf8ToString</span> <span class='hs-varid'>msg</span><span class='hs-layout'>)</span> <span class='hs-varid'>q</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span>
<a name="line-306"></a>                       <span class='hs-layout'>(</span><span class='hs-varid'>inQuotes</span> <span class='hs-varop'>.</span> <span class='hs-varid'>fromByteString</span><span class='hs-layout'>)</span>
<a name="line-307"></a>        <span class='hs-varid'>utf8ToString</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>T</span><span class='hs-varop'>.</span><span class='hs-varid'>unpack</span> <span class='hs-varop'>.</span> <span class='hs-conid'>TE</span><span class='hs-varop'>.</span><span class='hs-varid'>decodeUtf8</span>
<a name="line-308"></a>        <span class='hs-varid'>sub</span> <span class='hs-layout'>(</span><span class='hs-conid'>Plain</span>  <span class='hs-varid'>b</span><span class='hs-layout'>)</span>      <span class='hs-keyglyph'>=</span> <span class='hs-varid'>pure</span> <span class='hs-varid'>b</span>
<a name="line-309"></a>        <span class='hs-varid'>sub</span> <span class='hs-layout'>(</span><span class='hs-conid'>Escape</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>      <span class='hs-keyglyph'>=</span> <span class='hs-varid'>quote</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-varid'>escapeStringConn</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>s</span>
<a name="line-310"></a>        <span class='hs-varid'>sub</span> <span class='hs-layout'>(</span><span class='hs-conid'>EscapeByteA</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>quote</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-varid'>escapeByteaConn</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>s</span>
<a name="line-311"></a>        <span class='hs-varid'>sub</span> <span class='hs-layout'>(</span><span class='hs-conid'>Many</span>  <span class='hs-varid'>ys</span><span class='hs-layout'>)</span>      <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mconcat</span> <span class='hs-varop'>&lt;$&gt;</span> <span class='hs-varid'>mapM</span> <span class='hs-varid'>sub</span> <span class='hs-varid'>ys</span>
<a name="line-312"></a>        <span class='hs-varid'>split</span> <span class='hs-varid'>s</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fromByteString</span> <span class='hs-varid'>h</span> <span class='hs-conop'>:</span> <span class='hs-keyword'>if</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>null</span> <span class='hs-varid'>t</span> <span class='hs-keyword'>then</span> <span class='hs-conid'>[]</span> <span class='hs-keyword'>else</span> <span class='hs-varid'>split</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>tail</span> <span class='hs-varid'>t</span><span class='hs-layout'>)</span>
<a name="line-313"></a>            <span class='hs-keyword'>where</span> <span class='hs-layout'>(</span><span class='hs-varid'>h</span><span class='hs-layout'>,</span><span class='hs-varid'>t</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>break</span> <span class='hs-layout'>(</span><span class='hs-varop'>==</span><span class='hs-chr'>'?'</span><span class='hs-layout'>)</span> <span class='hs-varid'>s</span>
<a name="line-314"></a>        <span class='hs-varid'>zipParams</span> <span class='hs-layout'>(</span><span class='hs-varid'>t</span><span class='hs-conop'>:</span><span class='hs-varid'>ts</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>p</span><span class='hs-conop'>:</span><span class='hs-varid'>ps</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>t</span> <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>p</span> <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>zipParams</span> <span class='hs-varid'>ts</span> <span class='hs-varid'>ps</span>
<a name="line-315"></a>        <span class='hs-varid'>zipParams</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>t</span><span class='hs-keyglyph'>]</span> <span class='hs-conid'>[]</span>        <span class='hs-keyglyph'>=</span> <span class='hs-varid'>t</span>
<a name="line-316"></a>        <span class='hs-varid'>zipParams</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fmtError</span> <span class='hs-layout'>(</span><span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>count</span> <span class='hs-chr'>'?'</span> <span class='hs-varid'>template</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span>
<a name="line-317"></a>                                  <span class='hs-str'>" '?' characters, but "</span> <span class='hs-varop'>++</span>
<a name="line-318"></a>                                  <span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-varid'>length</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span> <span class='hs-str'>" parameters"</span><span class='hs-layout'>)</span> <span class='hs-varid'>q</span> <span class='hs-varid'>xs</span>
<a name="line-319"></a>
<a name="line-320"></a><a name="execute"></a><span class='hs-comment'>-- | Execute an @INSERT@, @UPDATE@, or other SQL query that is not</span>
<a name="line-321"></a><span class='hs-comment'>-- expected to return results.</span>
<a name="line-322"></a><span class='hs-comment'>--</span>
<a name="line-323"></a><span class='hs-comment'>-- Returns the number of rows affected.</span>
<a name="line-324"></a><span class='hs-comment'>--</span>
<a name="line-325"></a><span class='hs-comment'>-- Throws 'FormatError' if the query could not be formatted correctly.</span>
<a name="line-326"></a><span class='hs-definition'>execute</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>Int64</span>
<a name="line-327"></a><span class='hs-definition'>execute</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-328"></a>  <span class='hs-varid'>result</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>exec</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>=&lt;&lt;</span> <span class='hs-varid'>formatQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span>
<a name="line-329"></a>  <span class='hs-varid'>finishExecute</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>result</span>
<a name="line-330"></a>
<a name="line-331"></a><a name="executeMany"></a><span class='hs-comment'>-- | Execute a multi-row @INSERT@, @UPDATE@, or other SQL query that is not</span>
<a name="line-332"></a><span class='hs-comment'>-- expected to return results.</span>
<a name="line-333"></a><span class='hs-comment'>--</span>
<a name="line-334"></a><span class='hs-comment'>-- Returns the number of rows affected.</span>
<a name="line-335"></a><span class='hs-comment'>--</span>
<a name="line-336"></a><span class='hs-comment'>-- Throws 'FormatError' if the query could not be formatted correctly.</span>
<a name="line-337"></a><span class='hs-definition'>executeMany</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>q</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>Int64</span>
<a name="line-338"></a><span class='hs-definition'>executeMany</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-num'>0</span>
<a name="line-339"></a><span class='hs-definition'>executeMany</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-340"></a>  <span class='hs-varid'>result</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>exec</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>=&lt;&lt;</span> <span class='hs-varid'>formatMany</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>qs</span>
<a name="line-341"></a>  <span class='hs-varid'>finishExecute</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>result</span>
<a name="line-342"></a>
<a name="line-343"></a><a name="returning"></a><span class='hs-comment'>-- | Execute @INSERT ... RETURNING@, @UPDATE ... RETURNING@, or other SQL</span>
<a name="line-344"></a><span class='hs-comment'>-- query that accepts multi-row input and is expected to return results.</span>
<a name="line-345"></a><span class='hs-comment'>-- Note that it is possible to write</span>
<a name="line-346"></a><span class='hs-comment'>--    @'query' conn "INSERT ... RETURNING ..." ...@</span>
<a name="line-347"></a><span class='hs-comment'>-- in cases where you are only inserting a single row,  and do not need</span>
<a name="line-348"></a><span class='hs-comment'>-- functionality analogous to 'executeMany'.</span>
<a name="line-349"></a><span class='hs-comment'>--</span>
<a name="line-350"></a><span class='hs-comment'>-- Throws 'FormatError' if the query could not be formatted correctly.</span>
<a name="line-351"></a><span class='hs-definition'>returning</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>,</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>q</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-352"></a><span class='hs-definition'>returning</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-conid'>[]</span>
<a name="line-353"></a><span class='hs-definition'>returning</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-354"></a>  <span class='hs-varid'>result</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>exec</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>=&lt;&lt;</span> <span class='hs-varid'>formatMany</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>qs</span>
<a name="line-355"></a>  <span class='hs-varid'>finishQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>result</span>
<a name="line-356"></a>
<a name="line-357"></a><a name="query"></a><span class='hs-comment'>-- | Perform a @SELECT@ or other SQL query that is expected to return</span>
<a name="line-358"></a><span class='hs-comment'>-- results. All results are retrieved and converted before this</span>
<a name="line-359"></a><span class='hs-comment'>-- function returns.</span>
<a name="line-360"></a><span class='hs-comment'>--</span>
<a name="line-361"></a><span class='hs-comment'>-- When processing large results, this function will consume a lot of</span>
<a name="line-362"></a><span class='hs-comment'>-- client-side memory.  Consider using 'fold' instead.</span>
<a name="line-363"></a><span class='hs-comment'>--</span>
<a name="line-364"></a><span class='hs-comment'>-- Exceptions that may be thrown:</span>
<a name="line-365"></a><span class='hs-comment'>--</span>
<a name="line-366"></a><span class='hs-comment'>-- * 'FormatError': the query string could not be formatted correctly.</span>
<a name="line-367"></a><span class='hs-comment'>--</span>
<a name="line-368"></a><span class='hs-comment'>-- * 'QueryError': the result contains no columns (i.e. you should be</span>
<a name="line-369"></a><span class='hs-comment'>--   using 'execute' instead of 'query').</span>
<a name="line-370"></a><span class='hs-comment'>--</span>
<a name="line-371"></a><span class='hs-comment'>-- * 'ResultError': result conversion failed.</span>
<a name="line-372"></a><span class='hs-definition'>query</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>,</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-373"></a><span class='hs-definition'>query</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>queryWith</span> <span class='hs-varid'>fromRow</span>
<a name="line-374"></a>
<a name="line-375"></a><a name="query_"></a><span class='hs-comment'>-- | A version of 'query' that does not perform query substitution.</span>
<a name="line-376"></a><span class='hs-definition'>query_</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-377"></a><span class='hs-definition'>query_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>queryWith_</span> <span class='hs-varid'>fromRow</span>
<a name="line-378"></a>
<a name="line-379"></a><a name="queryWith"></a><span class='hs-comment'>-- | A version of 'query' taking parser as argument</span>
<a name="line-380"></a><span class='hs-definition'>queryWith</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>RowParser</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-381"></a><span class='hs-definition'>queryWith</span> <span class='hs-varid'>parser</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-382"></a>  <span class='hs-varid'>result</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>exec</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>=&lt;&lt;</span> <span class='hs-varid'>formatQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span>
<a name="line-383"></a>  <span class='hs-varid'>finishQueryWith</span> <span class='hs-varid'>parser</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>result</span>
<a name="line-384"></a>
<a name="line-385"></a><a name="queryWith_"></a><span class='hs-comment'>-- | A version of 'query_' taking parser as argument</span>
<a name="line-386"></a><span class='hs-definition'>queryWith_</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>RowParser</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-387"></a><span class='hs-definition'>queryWith_</span> <span class='hs-varid'>parser</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span><span class='hs-keyglyph'>@</span><span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>que</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-388"></a>  <span class='hs-varid'>result</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>exec</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>que</span>
<a name="line-389"></a>  <span class='hs-varid'>finishQueryWith</span> <span class='hs-varid'>parser</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>result</span>
<a name="line-390"></a>
<a name="line-391"></a><span class='hs-comment'>-- | Perform a @SELECT@ or other SQL query that is expected to return</span>
<a name="line-392"></a><span class='hs-comment'>-- results. Results are streamed incrementally from the server, and</span>
<a name="line-393"></a><span class='hs-comment'>-- consumed via a left fold.</span>
<a name="line-394"></a><span class='hs-comment'>--</span>
<a name="line-395"></a><span class='hs-comment'>-- When dealing with small results, it may be simpler (and perhaps</span>
<a name="line-396"></a><span class='hs-comment'>-- faster) to use 'query' instead.</span>
<a name="line-397"></a><span class='hs-comment'>--</span>
<a name="line-398"></a><span class='hs-comment'>-- This fold is /not/ strict. The stream consumer is responsible for</span>
<a name="line-399"></a><span class='hs-comment'>-- forcing the evaluation of its result to avoid space leaks.</span>
<a name="line-400"></a><span class='hs-comment'>--</span>
<a name="line-401"></a><span class='hs-comment'>-- Exceptions that may be thrown:</span>
<a name="line-402"></a><span class='hs-comment'>--</span>
<a name="line-403"></a><span class='hs-comment'>-- * 'FormatError': the query string could not be formatted correctly.</span>
<a name="line-404"></a><span class='hs-comment'>--</span>
<a name="line-405"></a><span class='hs-comment'>-- * 'QueryError': the result contains no columns (i.e. you should be</span>
<a name="line-406"></a><span class='hs-comment'>--   using 'execute' instead of 'query').</span>
<a name="line-407"></a><span class='hs-comment'>--</span>
<a name="line-408"></a><span class='hs-comment'>-- * 'ResultError': result conversion failed.</span>
<a name="line-409"></a>
<a name="line-410"></a><a name="fold"></a><span class='hs-definition'>fold</span>            <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>row</span><span class='hs-layout'>,</span> <span class='hs-conid'>ToRow</span> <span class='hs-varid'>params</span> <span class='hs-layout'>)</span>
<a name="line-411"></a>                <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span>
<a name="line-412"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>
<a name="line-413"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>params</span>
<a name="line-414"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>
<a name="line-415"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>row</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-416"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-417"></a><span class='hs-definition'>fold</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldWithOptions</span> <span class='hs-varid'>defaultFoldOptions</span>
<a name="line-418"></a>
<a name="line-419"></a><a name="FetchQuantity"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>FetchQuantity</span>
<a name="line-420"></a>   <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Automatic</span>
<a name="line-421"></a>   <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Fixed</span> <span class='hs-varop'>!</span><span class='hs-conid'>Int</span>
<a name="line-422"></a>
<a name="line-423"></a><a name="FoldOptions"></a><span class='hs-keyword'>data</span> <span class='hs-conid'>FoldOptions</span>
<a name="line-424"></a>   <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FoldOptions</span> <span class='hs-layout'>{</span>
<a name="line-425"></a>       <span class='hs-varid'>fetchQuantity</span>   <span class='hs-keyglyph'>::</span> <span class='hs-varop'>!</span><span class='hs-conid'>FetchQuantity</span><span class='hs-layout'>,</span>
<a name="line-426"></a>       <span class='hs-varid'>transactionMode</span> <span class='hs-keyglyph'>::</span> <span class='hs-varop'>!</span><span class='hs-conid'>TransactionMode</span>
<a name="line-427"></a>     <span class='hs-layout'>}</span>
<a name="line-428"></a>
<a name="line-429"></a><a name="defaultFoldOptions"></a><span class='hs-definition'>defaultFoldOptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FoldOptions</span>
<a name="line-430"></a><span class='hs-definition'>defaultFoldOptions</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>FoldOptions</span> <span class='hs-layout'>{</span>
<a name="line-431"></a>      <span class='hs-varid'>fetchQuantity</span>   <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Automatic</span><span class='hs-layout'>,</span>
<a name="line-432"></a>      <span class='hs-varid'>transactionMode</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>TransactionMode</span> <span class='hs-conid'>ReadCommitted</span> <span class='hs-conid'>ReadOnly</span>
<a name="line-433"></a>    <span class='hs-layout'>}</span>
<a name="line-434"></a>
<a name="line-435"></a><a name="foldWithOptions"></a><span class='hs-definition'>foldWithOptions</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>row</span><span class='hs-layout'>,</span> <span class='hs-conid'>ToRow</span> <span class='hs-varid'>params</span> <span class='hs-layout'>)</span>
<a name="line-436"></a>                <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>FoldOptions</span>
<a name="line-437"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span>
<a name="line-438"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>
<a name="line-439"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>params</span>
<a name="line-440"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>
<a name="line-441"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>row</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-442"></a>                <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-443"></a><span class='hs-definition'>foldWithOptions</span> <span class='hs-varid'>opts</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span> <span class='hs-varid'>a</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-444"></a>    <span class='hs-varid'>q</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>formatQuery</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span>
<a name="line-445"></a>    <span class='hs-varid'>doFold</span> <span class='hs-varid'>opts</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>q</span><span class='hs-layout'>)</span> <span class='hs-varid'>a</span> <span class='hs-varid'>f</span>
<a name="line-446"></a>
<a name="line-447"></a><a name="fold_"></a><span class='hs-comment'>-- | A version of 'fold' that does not perform query substitution.</span>
<a name="line-448"></a><span class='hs-definition'>fold_</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span>
<a name="line-449"></a>         <span class='hs-conid'>Connection</span>
<a name="line-450"></a>      <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>                  <span class='hs-comment'>-- ^ Query.</span>
<a name="line-451"></a>      <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>                      <span class='hs-comment'>-- ^ Initial state for result consumer.</span>
<a name="line-452"></a>      <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>       <span class='hs-comment'>-- ^ Result consumer.</span>
<a name="line-453"></a>      <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-454"></a><span class='hs-definition'>fold_</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>foldWithOptions_</span> <span class='hs-varid'>defaultFoldOptions</span>
<a name="line-455"></a>
<a name="line-456"></a>
<a name="line-457"></a><a name="foldWithOptions_"></a><span class='hs-definition'>foldWithOptions_</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span>
<a name="line-458"></a>                    <span class='hs-conid'>FoldOptions</span>
<a name="line-459"></a>                 <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span>
<a name="line-460"></a>                 <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>             <span class='hs-comment'>-- ^ Query.</span>
<a name="line-461"></a>                 <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>                 <span class='hs-comment'>-- ^ Initial state for result consumer.</span>
<a name="line-462"></a>                 <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>  <span class='hs-comment'>-- ^ Result consumer.</span>
<a name="line-463"></a>                 <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-464"></a><span class='hs-definition'>foldWithOptions_</span> <span class='hs-varid'>opts</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>query</span> <span class='hs-varid'>a</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>doFold</span> <span class='hs-varid'>opts</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>query</span> <span class='hs-varid'>query</span> <span class='hs-varid'>a</span> <span class='hs-varid'>f</span>
<a name="line-465"></a>
<a name="line-466"></a>
<a name="line-467"></a><a name="doFold"></a><span class='hs-definition'>doFold</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>row</span> <span class='hs-layout'>)</span>
<a name="line-468"></a>       <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>FoldOptions</span>
<a name="line-469"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span>
<a name="line-470"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>
<a name="line-471"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>
<a name="line-472"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>
<a name="line-473"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>row</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span>
<a name="line-474"></a>       <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span>
<a name="line-475"></a><span class='hs-definition'>doFold</span> <span class='hs-conid'>FoldOptions</span><span class='hs-layout'>{</span><span class='hs-keyglyph'>..</span><span class='hs-layout'>}</span> <span class='hs-varid'>conn</span> <span class='hs-sel'>_template</span> <span class='hs-varid'>q</span> <span class='hs-varid'>a0</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-476"></a>    <span class='hs-varid'>stat</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>withConnection</span> <span class='hs-varid'>conn</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>transactionStatus</span>
<a name="line-477"></a>    <span class='hs-keyword'>case</span> <span class='hs-varid'>stat</span> <span class='hs-keyword'>of</span>
<a name="line-478"></a>      <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TransIdle</span>    <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>withTransactionMode</span> <span class='hs-varid'>transactionMode</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>go</span>
<a name="line-479"></a>      <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TransInTrans</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>go</span>
<a name="line-480"></a>      <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TransActive</span>  <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>fail</span> <span class='hs-str'>"foldWithOpts FIXME:  PQ.TransActive"</span>
<a name="line-481"></a>         <span class='hs-comment'>-- This _shouldn't_ occur in the current incarnation of</span>
<a name="line-482"></a>         <span class='hs-comment'>-- the library,  as we aren't using libpq asynchronously.</span>
<a name="line-483"></a>         <span class='hs-comment'>-- However,  it could occur in future incarnations of</span>
<a name="line-484"></a>         <span class='hs-comment'>-- this library or if client code uses the Internal module</span>
<a name="line-485"></a>         <span class='hs-comment'>-- to use raw libpq commands on postgresql-simple connections.</span>
<a name="line-486"></a>      <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TransInError</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>fail</span> <span class='hs-str'>"foldWithOpts FIXME:  PQ.TransInError"</span>
<a name="line-487"></a>         <span class='hs-comment'>-- This should be turned into a better error message.</span>
<a name="line-488"></a>         <span class='hs-comment'>-- It is probably a bad idea to automatically roll</span>
<a name="line-489"></a>         <span class='hs-comment'>-- back the transaction and start another.</span>
<a name="line-490"></a>      <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TransUnknown</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>fail</span> <span class='hs-str'>"foldWithOpts FIXME:  PQ.TransUnknown"</span>
<a name="line-491"></a>         <span class='hs-comment'>-- Not sure what this means.</span>
<a name="line-492"></a>  <span class='hs-keyword'>where</span>
<a name="line-493"></a>    <span class='hs-varid'>declare</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-494"></a>        <span class='hs-varid'>name</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>newTempName</span> <span class='hs-varid'>conn</span>
<a name="line-495"></a>        <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>execute_</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>$</span> <span class='hs-varid'>mconcat</span>
<a name="line-496"></a>                 <span class='hs-keyglyph'>[</span> <span class='hs-str'>"DECLARE "</span><span class='hs-layout'>,</span> <span class='hs-varid'>name</span><span class='hs-layout'>,</span> <span class='hs-str'>" NO SCROLL CURSOR FOR "</span><span class='hs-layout'>,</span> <span class='hs-varid'>q</span> <span class='hs-keyglyph'>]</span>
<a name="line-497"></a>        <span class='hs-varid'>return</span> <span class='hs-varid'>name</span>
<a name="line-498"></a>    <span class='hs-varid'>fetch</span> <span class='hs-layout'>(</span><span class='hs-conid'>Query</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>query_</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>$</span>
<a name="line-499"></a>        <span class='hs-conid'>Query</span> <span class='hs-layout'>(</span><span class='hs-varid'>toByteString</span> <span class='hs-layout'>(</span><span class='hs-varid'>fromByteString</span> <span class='hs-str'>"FETCH FORWARD "</span>
<a name="line-500"></a>                             <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>integral</span> <span class='hs-varid'>chunkSize</span>
<a name="line-501"></a>                             <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>fromByteString</span> <span class='hs-str'>" FROM "</span>
<a name="line-502"></a>                             <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>fromByteString</span> <span class='hs-varid'>name</span>
<a name="line-503"></a>                            <span class='hs-layout'>)</span><span class='hs-layout'>)</span>
<a name="line-504"></a>    <span class='hs-varid'>close</span> <span class='hs-varid'>name</span> <span class='hs-keyglyph'>=</span>
<a name="line-505"></a>        <span class='hs-layout'>(</span><span class='hs-varid'>execute_</span> <span class='hs-varid'>conn</span> <span class='hs-layout'>(</span><span class='hs-str'>"CLOSE "</span> <span class='hs-varop'>&lt;&gt;</span> <span class='hs-varid'>name</span><span class='hs-layout'>)</span> <span class='hs-varop'>&gt;&gt;</span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span> <span class='hs-varop'>`</span><span class='hs-conid'>E</span><span class='hs-varop'>.</span><span class='hs-varid'>catch</span><span class='hs-varop'>`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>ex</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-506"></a>            <span class='hs-comment'>-- Don't throw exception if CLOSE failed because the transaction is</span>
<a name="line-507"></a>            <span class='hs-comment'>-- aborted.  Otherwise, it will throw away the original error.</span>
<a name="line-508"></a>            <span class='hs-keyword'>if</span> <span class='hs-varid'>isFailedTransactionError</span> <span class='hs-varid'>ex</span> <span class='hs-keyword'>then</span> <span class='hs-varid'>return</span> <span class='hs-conid'>()</span> <span class='hs-keyword'>else</span> <span class='hs-varid'>throwIO</span> <span class='hs-varid'>ex</span>
<a name="line-509"></a>
<a name="line-510"></a>    <span class='hs-varid'>go</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>bracket</span> <span class='hs-varid'>declare</span> <span class='hs-varid'>close</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>name</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-511"></a>         <span class='hs-keyword'>let</span> <span class='hs-varid'>loop</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-512"></a>                 <span class='hs-varid'>rs</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>fetch</span> <span class='hs-varid'>name</span>
<a name="line-513"></a>                 <span class='hs-keyword'>if</span> <span class='hs-varid'>null</span> <span class='hs-varid'>rs</span> <span class='hs-keyword'>then</span> <span class='hs-varid'>return</span> <span class='hs-varid'>a</span> <span class='hs-keyword'>else</span> <span class='hs-varid'>foldM</span> <span class='hs-varid'>f</span> <span class='hs-varid'>a</span> <span class='hs-varid'>rs</span> <span class='hs-varop'>&gt;&gt;=</span> <span class='hs-varid'>loop</span>
<a name="line-514"></a>          <span class='hs-keyword'>in</span> <span class='hs-varid'>loop</span> <span class='hs-varid'>a0</span>
<a name="line-515"></a>
<a name="line-516"></a><span class='hs-comment'>-- FIXME: choose the Automatic chunkSize more intelligently</span>
<a name="line-517"></a><span class='hs-comment'>--   One possibility is to use the type of the results,  although this</span>
<a name="line-518"></a><span class='hs-comment'>--   still isn't a perfect solution, given that common types (e.g. text)</span>
<a name="line-519"></a><span class='hs-comment'>--   are of highly variable size.</span>
<a name="line-520"></a><span class='hs-comment'>--   A refinement of this technique is to pick this number adaptively</span>
<a name="line-521"></a><span class='hs-comment'>--   as results are read in from the database.</span>
<a name="line-522"></a>    <span class='hs-varid'>chunkSize</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>fetchQuantity</span> <span class='hs-keyword'>of</span>
<a name="line-523"></a>                 <span class='hs-conid'>Automatic</span>   <span class='hs-keyglyph'>-&gt;</span> <span class='hs-num'>256</span>
<a name="line-524"></a>                 <span class='hs-conid'>Fixed</span> <span class='hs-varid'>n</span>     <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>n</span>
<a name="line-525"></a>
<a name="line-526"></a><a name="forEach"></a><span class='hs-comment'>-- | A version of 'fold' that does not transform a state value.</span>
<a name="line-527"></a><span class='hs-definition'>forEach</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>ToRow</span> <span class='hs-varid'>q</span><span class='hs-layout'>,</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span>
<a name="line-528"></a>           <span class='hs-conid'>Connection</span>
<a name="line-529"></a>        <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>                <span class='hs-comment'>-- ^ Query template.</span>
<a name="line-530"></a>        <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>q</span>                    <span class='hs-comment'>-- ^ Query parameters.</span>
<a name="line-531"></a>        <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>         <span class='hs-comment'>-- ^ Result consumer.</span>
<a name="line-532"></a>        <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-533"></a><span class='hs-definition'>forEach</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fold</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-varid'>qs</span> <span class='hs-conid'>()</span> <span class='hs-varop'>.</span> <span class='hs-varid'>const</span>
<a name="line-534"></a><span class='hs-comment'>{-# INLINE forEach #-}</span>
<a name="line-535"></a>
<a name="line-536"></a><a name="forEach_"></a><span class='hs-comment'>-- | A version of 'forEach' that does not perform query substitution.</span>
<a name="line-537"></a><span class='hs-definition'>forEach_</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span>
<a name="line-538"></a>            <span class='hs-conid'>Connection</span>
<a name="line-539"></a>         <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span>                <span class='hs-comment'>-- ^ Query template.</span>
<a name="line-540"></a>         <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span><span class='hs-layout'>)</span>         <span class='hs-comment'>-- ^ Result consumer.</span>
<a name="line-541"></a>         <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-conid'>()</span>
<a name="line-542"></a><span class='hs-definition'>forEach_</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fold_</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>template</span> <span class='hs-conid'>()</span> <span class='hs-varop'>.</span> <span class='hs-varid'>const</span>
<a name="line-543"></a><span class='hs-comment'>{-# INLINE forEach_ #-}</span>
<a name="line-544"></a>
<a name="line-545"></a><a name="forM'"></a><span class='hs-definition'>forM'</span> <span class='hs-keyglyph'>::</span> <span class='hs-layout'>(</span><span class='hs-conid'>Ord</span> <span class='hs-varid'>n</span><span class='hs-layout'>,</span> <span class='hs-conid'>Num</span> <span class='hs-varid'>n</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-varid'>n</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>n</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-varid'>a</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>a</span><span class='hs-keyglyph'>]</span>
<a name="line-546"></a><span class='hs-definition'>forM'</span> <span class='hs-varid'>lo</span> <span class='hs-varid'>hi</span> <span class='hs-varid'>m</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>loop</span> <span class='hs-varid'>hi</span> <span class='hs-conid'>[]</span>
<a name="line-547"></a>  <span class='hs-keyword'>where</span>
<a name="line-548"></a>    <span class='hs-varid'>loop</span> <span class='hs-varop'>!</span><span class='hs-varid'>n</span> <span class='hs-varop'>!</span><span class='hs-keyword'>as</span>
<a name="line-549"></a>      <span class='hs-keyglyph'>|</span> <span class='hs-varid'>n</span> <span class='hs-varop'>&lt;</span> <span class='hs-varid'>lo</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>return</span> <span class='hs-keyword'>as</span>
<a name="line-550"></a>      <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-551"></a>           <span class='hs-varid'>a</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>m</span> <span class='hs-varid'>n</span>
<a name="line-552"></a>           <span class='hs-varid'>loop</span> <span class='hs-layout'>(</span><span class='hs-varid'>n</span><span class='hs-comment'>-</span><span class='hs-num'>1</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span><span class='hs-conop'>:</span><span class='hs-keyword'>as</span><span class='hs-layout'>)</span>
<a name="line-553"></a>
<a name="line-554"></a><a name="finishQuery"></a><span class='hs-definition'>finishQuery</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>FromRow</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>=&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>Result</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-555"></a><span class='hs-definition'>finishQuery</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>finishQueryWith</span> <span class='hs-varid'>fromRow</span>
<a name="line-556"></a>
<a name="line-557"></a><a name="finishQueryWith"></a><span class='hs-definition'>finishQueryWith</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>RowParser</span> <span class='hs-varid'>r</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Connection</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>Result</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>IO</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>r</span><span class='hs-keyglyph'>]</span>
<a name="line-558"></a><span class='hs-definition'>finishQueryWith</span> <span class='hs-varid'>parser</span> <span class='hs-varid'>conn</span> <span class='hs-varid'>q</span> <span class='hs-varid'>result</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-559"></a>  <span class='hs-varid'>status</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>resultStatus</span> <span class='hs-varid'>result</span>
<a name="line-560"></a>  <span class='hs-keyword'>case</span> <span class='hs-varid'>status</span> <span class='hs-keyword'>of</span>
<a name="line-561"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>EmptyQuery</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-562"></a>        <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>QueryError</span> <span class='hs-str'>"query: Empty query"</span> <span class='hs-varid'>q</span>
<a name="line-563"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>CommandOk</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-564"></a>        <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>QueryError</span> <span class='hs-str'>"query resulted in a command response"</span> <span class='hs-varid'>q</span>
<a name="line-565"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>TuplesOk</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-566"></a>        <span class='hs-keyword'>let</span> <span class='hs-varid'>unCol</span> <span class='hs-layout'>(</span><span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>Col</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>fromIntegral</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>Int</span>
<a name="line-567"></a>        <span class='hs-varid'>nrows</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>ntuples</span> <span class='hs-varid'>result</span>
<a name="line-568"></a>        <span class='hs-varid'>ncols</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>nfields</span> <span class='hs-varid'>result</span>
<a name="line-569"></a>        <span class='hs-varid'>forM'</span> <span class='hs-num'>0</span> <span class='hs-layout'>(</span><span class='hs-varid'>nrows</span><span class='hs-comment'>-</span><span class='hs-num'>1</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>row</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-570"></a>           <span class='hs-keyword'>let</span> <span class='hs-varid'>rw</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Row</span> <span class='hs-varid'>row</span> <span class='hs-varid'>result</span>
<a name="line-571"></a>           <span class='hs-varid'>okvc</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>runConversion</span> <span class='hs-layout'>(</span><span class='hs-varid'>runStateT</span> <span class='hs-layout'>(</span><span class='hs-varid'>runReaderT</span> <span class='hs-layout'>(</span><span class='hs-varid'>unRP</span> <span class='hs-varid'>parser</span><span class='hs-layout'>)</span> <span class='hs-varid'>rw</span><span class='hs-layout'>)</span> <span class='hs-num'>0</span><span class='hs-layout'>)</span> <span class='hs-varid'>conn</span>
<a name="line-572"></a>           <span class='hs-keyword'>case</span> <span class='hs-varid'>okvc</span> <span class='hs-keyword'>of</span>
<a name="line-573"></a>             <span class='hs-conid'>Ok</span> <span class='hs-layout'>(</span><span class='hs-varid'>val</span><span class='hs-layout'>,</span><span class='hs-varid'>col</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>col</span> <span class='hs-varop'>==</span> <span class='hs-varid'>ncols</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>return</span> <span class='hs-varid'>val</span>
<a name="line-574"></a>                          <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-575"></a>                              <span class='hs-varid'>vals</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>forM'</span> <span class='hs-num'>0</span> <span class='hs-layout'>(</span><span class='hs-varid'>ncols</span><span class='hs-comment'>-</span><span class='hs-num'>1</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>c</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyword'>do</span>
<a name="line-576"></a>                                  <span class='hs-varid'>tinfo</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-varid'>getTypeInfo</span> <span class='hs-varid'>conn</span> <span class='hs-varop'>=&lt;&lt;</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>ftype</span> <span class='hs-varid'>result</span> <span class='hs-varid'>c</span>
<a name="line-577"></a>                                  <span class='hs-varid'>v</span> <span class='hs-keyglyph'>&lt;-</span> <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-varid'>getvalue</span> <span class='hs-varid'>result</span> <span class='hs-varid'>row</span> <span class='hs-varid'>c</span>
<a name="line-578"></a>                                  <span class='hs-varid'>return</span> <span class='hs-layout'>(</span> <span class='hs-varid'>tinfo</span>
<a name="line-579"></a>                                         <span class='hs-layout'>,</span> <span class='hs-varid'>fmap</span> <span class='hs-varid'>ellipsis</span> <span class='hs-varid'>v</span>       <span class='hs-layout'>)</span>
<a name="line-580"></a>                              <span class='hs-varid'>throw</span> <span class='hs-layout'>(</span><span class='hs-conid'>ConversionFailed</span>
<a name="line-581"></a>                               <span class='hs-layout'>(</span><span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-varid'>unCol</span> <span class='hs-varid'>ncols</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span> <span class='hs-str'>" values: "</span> <span class='hs-varop'>++</span> <span class='hs-varid'>show</span> <span class='hs-varid'>vals</span><span class='hs-layout'>)</span>
<a name="line-582"></a>                               <span class='hs-conid'>Nothing</span>
<a name="line-583"></a>                               <span class='hs-str'>""</span>
<a name="line-584"></a>                               <span class='hs-layout'>(</span><span class='hs-varid'>show</span> <span class='hs-layout'>(</span><span class='hs-varid'>unCol</span> <span class='hs-varid'>col</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span> <span class='hs-str'>" slots in target type"</span><span class='hs-layout'>)</span>
<a name="line-585"></a>                               <span class='hs-str'>"mismatch between number of columns to \
<a name="line-586"></a>                               \convert and number in target type"</span><span class='hs-layout'>)</span>
<a name="line-587"></a>             <span class='hs-conid'>Errors</span> <span class='hs-conid'>[]</span>  <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>ConversionFailed</span> <span class='hs-str'>""</span> <span class='hs-conid'>Nothing</span> <span class='hs-str'>""</span> <span class='hs-str'>""</span> <span class='hs-str'>"unknown error"</span>
<a name="line-588"></a>             <span class='hs-conid'>Errors</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwIO</span> <span class='hs-varid'>x</span>
<a name="line-589"></a>             <span class='hs-conid'>Errors</span> <span class='hs-varid'>xs</span>  <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>ManyErrors</span> <span class='hs-varid'>xs</span>
<a name="line-590"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>CopyOut</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-591"></a>        <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>QueryError</span> <span class='hs-str'>"query: COPY TO is not supported"</span> <span class='hs-varid'>q</span>
<a name="line-592"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>CopyIn</span> <span class='hs-keyglyph'>-&gt;</span>
<a name="line-593"></a>        <span class='hs-varid'>throwIO</span> <span class='hs-varop'>$</span> <span class='hs-conid'>QueryError</span> <span class='hs-str'>"query: COPY FROM is not supported"</span> <span class='hs-varid'>q</span>
<a name="line-594"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>BadResponse</span>   <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwResultError</span> <span class='hs-str'>"query"</span> <span class='hs-varid'>result</span> <span class='hs-varid'>status</span>
<a name="line-595"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>NonfatalError</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwResultError</span> <span class='hs-str'>"query"</span> <span class='hs-varid'>result</span> <span class='hs-varid'>status</span>
<a name="line-596"></a>    <span class='hs-conid'>PQ</span><span class='hs-varop'>.</span><span class='hs-conid'>FatalError</span>    <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>throwResultError</span> <span class='hs-str'>"query"</span> <span class='hs-varid'>result</span> <span class='hs-varid'>status</span>
<a name="line-597"></a>
<a name="line-598"></a><a name="ellipsis"></a><span class='hs-definition'>ellipsis</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ByteString</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>ByteString</span>
<a name="line-599"></a><span class='hs-definition'>ellipsis</span> <span class='hs-varid'>bs</span>
<a name="line-600"></a>    <span class='hs-keyglyph'>|</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>length</span> <span class='hs-varid'>bs</span> <span class='hs-varop'>&gt;</span> <span class='hs-num'>15</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>take</span> <span class='hs-num'>10</span> <span class='hs-varid'>bs</span> <span class='hs-varop'>`</span><span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>append</span><span class='hs-varop'>`</span> <span class='hs-str'>"[...]"</span>
<a name="line-601"></a>    <span class='hs-keyglyph'>|</span> <span class='hs-varid'>otherwise</span>        <span class='hs-keyglyph'>=</span> <span class='hs-varid'>bs</span>
<a name="line-602"></a>
<a name="line-603"></a><a name="fmtError"></a><span class='hs-definition'>fmtError</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>String</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-conid'>Query</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Action</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-&gt;</span> <span class='hs-varid'>a</span>
<a name="line-604"></a><span class='hs-definition'>fmtError</span> <span class='hs-varid'>msg</span> <span class='hs-varid'>q</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>throw</span> <span class='hs-conid'>FormatError</span> <span class='hs-layout'>{</span>
<a name="line-605"></a>                      <span class='hs-varid'>fmtMessage</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>msg</span>
<a name="line-606"></a>                    <span class='hs-layout'>,</span> <span class='hs-varid'>fmtQuery</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>q</span>
<a name="line-607"></a>                    <span class='hs-layout'>,</span> <span class='hs-varid'>fmtParams</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>map</span> <span class='hs-varid'>twiddle</span> <span class='hs-varid'>xs</span>
<a name="line-608"></a>                    <span class='hs-layout'>}</span>
<a name="line-609"></a>  <span class='hs-keyword'>where</span> <span class='hs-varid'>twiddle</span> <span class='hs-layout'>(</span><span class='hs-conid'>Plain</span> <span class='hs-varid'>b</span><span class='hs-layout'>)</span>       <span class='hs-keyglyph'>=</span> <span class='hs-varid'>toByteString</span> <span class='hs-varid'>b</span>
<a name="line-610"></a>        <span class='hs-varid'>twiddle</span> <span class='hs-layout'>(</span><span class='hs-conid'>Escape</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span>      <span class='hs-keyglyph'>=</span> <span class='hs-varid'>s</span>
<a name="line-611"></a>        <span class='hs-varid'>twiddle</span> <span class='hs-layout'>(</span><span class='hs-conid'>EscapeByteA</span> <span class='hs-varid'>s</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>s</span>
<a name="line-612"></a>        <span class='hs-varid'>twiddle</span> <span class='hs-layout'>(</span><span class='hs-conid'>Many</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span>       <span class='hs-keyglyph'>=</span> <span class='hs-conid'>B</span><span class='hs-varop'>.</span><span class='hs-varid'>concat</span> <span class='hs-layout'>(</span><span class='hs-varid'>map</span> <span class='hs-varid'>twiddle</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span>
<a name="line-613"></a>
<a name="line-614"></a><span class='hs-comment'>-- $use</span>
<a name="line-615"></a><span class='hs-comment'>--</span>
<a name="line-616"></a><span class='hs-comment'>-- SQL-based applications are somewhat notorious for their</span>
<a name="line-617"></a><span class='hs-comment'>-- susceptibility to attacks through the injection of maliciously</span>
<a name="line-618"></a><span class='hs-comment'>-- crafted data. The primary reason for widespread vulnerability to</span>
<a name="line-619"></a><span class='hs-comment'>-- SQL injections is that many applications are sloppy in handling</span>
<a name="line-620"></a><span class='hs-comment'>-- user data when constructing SQL queries.</span>
<a name="line-621"></a><span class='hs-comment'>--</span>
<a name="line-622"></a><span class='hs-comment'>-- This library provides a 'Query' type and a parameter substitution</span>
<a name="line-623"></a><span class='hs-comment'>-- facility to address both ease of use and security.</span>
<a name="line-624"></a>
<a name="line-625"></a><span class='hs-comment'>-- $querytype</span>
<a name="line-626"></a><span class='hs-comment'>--</span>
<a name="line-627"></a><span class='hs-comment'>-- A 'Query' is a @newtype@-wrapped 'ByteString'. It intentionally</span>
<a name="line-628"></a><span class='hs-comment'>-- exposes a tiny API that is not compatible with the 'ByteString'</span>
<a name="line-629"></a><span class='hs-comment'>-- API; this makes it difficult to construct queries from fragments of</span>
<a name="line-630"></a><span class='hs-comment'>-- strings.  The 'query' and 'execute' functions require queries to be</span>
<a name="line-631"></a><span class='hs-comment'>-- of type 'Query'.</span>
<a name="line-632"></a><span class='hs-comment'>--</span>
<a name="line-633"></a><span class='hs-comment'>-- To most easily construct a query, enable GHC's @OverloadedStrings@</span>
<a name="line-634"></a><span class='hs-comment'>-- language extension and write your query as a normal literal string.</span>
<a name="line-635"></a><span class='hs-comment'>--</span>
<a name="line-636"></a><span class='hs-comment'>-- &gt; {-# LANGUAGE OverloadedStrings #-}</span>
<a name="line-637"></a><span class='hs-comment'>-- &gt;</span>
<a name="line-638"></a><span class='hs-comment'>-- &gt; import Database.PostgreSQL.Simple</span>
<a name="line-639"></a><span class='hs-comment'>-- &gt;</span>
<a name="line-640"></a><span class='hs-comment'>-- &gt; hello = do</span>
<a name="line-641"></a><span class='hs-comment'>-- &gt;   conn &lt;- connect defaultConnectInfo</span>
<a name="line-642"></a><span class='hs-comment'>-- &gt;   query_ conn "select 2 + 2"</span>
<a name="line-643"></a><span class='hs-comment'>--</span>
<a name="line-644"></a><span class='hs-comment'>-- A 'Query' value does not represent the actual query that will be</span>
<a name="line-645"></a><span class='hs-comment'>-- executed, but is a template for constructing the final query.</span>
<a name="line-646"></a>
<a name="line-647"></a><span class='hs-comment'>-- $subst</span>
<a name="line-648"></a><span class='hs-comment'>--</span>
<a name="line-649"></a><span class='hs-comment'>-- Since applications need to be able to construct queries with</span>
<a name="line-650"></a><span class='hs-comment'>-- parameters that change, this library provides a query substitution</span>
<a name="line-651"></a><span class='hs-comment'>-- capability.</span>
<a name="line-652"></a><span class='hs-comment'>--</span>
<a name="line-653"></a><span class='hs-comment'>-- The 'Query' template accepted by 'query' and 'execute' can contain</span>
<a name="line-654"></a><span class='hs-comment'>-- any number of \"@?@\" characters.  Both 'query' and 'execute'</span>
<a name="line-655"></a><span class='hs-comment'>-- accept a third argument, typically a tuple. When constructing the</span>
<a name="line-656"></a><span class='hs-comment'>-- real query to execute, these functions replace the first \"@?@\" in</span>
<a name="line-657"></a><span class='hs-comment'>-- the template with the first element of the tuple, the second</span>
<a name="line-658"></a><span class='hs-comment'>-- \"@?@\" with the second element, and so on. If necessary, each</span>
<a name="line-659"></a><span class='hs-comment'>-- tuple element will be quoted and escaped prior to substitution;</span>
<a name="line-660"></a><span class='hs-comment'>-- this defeats the single most common injection vector for malicious</span>
<a name="line-661"></a><span class='hs-comment'>-- data.</span>
<a name="line-662"></a><span class='hs-comment'>--</span>
<a name="line-663"></a><span class='hs-comment'>-- For example, given the following 'Query' template:</span>
<a name="line-664"></a><span class='hs-comment'>--</span>
<a name="line-665"></a><span class='hs-comment'>-- &gt; select * from user where first_name = ? and age &gt; ?</span>
<a name="line-666"></a><span class='hs-comment'>--</span>
<a name="line-667"></a><span class='hs-comment'>-- And a tuple of this form:</span>
<a name="line-668"></a><span class='hs-comment'>--</span>
<a name="line-669"></a><span class='hs-comment'>-- &gt; ("Boris" :: String, 37 :: Int)</span>
<a name="line-670"></a><span class='hs-comment'>--</span>
<a name="line-671"></a><span class='hs-comment'>-- The query to be executed will look like this after substitution:</span>
<a name="line-672"></a><span class='hs-comment'>--</span>
<a name="line-673"></a><span class='hs-comment'>-- &gt; select * from user where first_name = 'Boris' and age &gt; 37</span>
<a name="line-674"></a><span class='hs-comment'>--</span>
<a name="line-675"></a><span class='hs-comment'>-- If there is a mismatch between the number of \"@?@\" characters in</span>
<a name="line-676"></a><span class='hs-comment'>-- your template and the number of elements in your tuple, a</span>
<a name="line-677"></a><span class='hs-comment'>-- 'FormatError' will be thrown.</span>
<a name="line-678"></a><span class='hs-comment'>--</span>
<a name="line-679"></a><span class='hs-comment'>-- Note that the substitution functions do not attempt to parse or</span>
<a name="line-680"></a><span class='hs-comment'>-- validate your query. It's up to you to write syntactically valid</span>
<a name="line-681"></a><span class='hs-comment'>-- SQL, and to ensure that each \"@?@\" in your query template is</span>
<a name="line-682"></a><span class='hs-comment'>-- matched with the right tuple element.</span>
<a name="line-683"></a>
<a name="line-684"></a><span class='hs-comment'>-- $inference</span>
<a name="line-685"></a><span class='hs-comment'>--</span>
<a name="line-686"></a><span class='hs-comment'>-- Automated type inference means that you will often be able to avoid</span>
<a name="line-687"></a><span class='hs-comment'>-- supplying explicit type signatures for the elements of a tuple.</span>
<a name="line-688"></a><span class='hs-comment'>-- However, sometimes the compiler will not be able to infer your</span>
<a name="line-689"></a><span class='hs-comment'>-- types. Consider a case where you write a numeric literal in a</span>
<a name="line-690"></a><span class='hs-comment'>-- parameter tuple:</span>
<a name="line-691"></a><span class='hs-comment'>--</span>
<a name="line-692"></a><span class='hs-comment'>-- &gt; query conn "select ? + ?" (40,2)</span>
<a name="line-693"></a><span class='hs-comment'>--</span>
<a name="line-694"></a><span class='hs-comment'>-- The above query will be rejected by the compiler, because it does</span>
<a name="line-695"></a><span class='hs-comment'>-- not know the specific numeric types of the literals @40@ and @2@.</span>
<a name="line-696"></a><span class='hs-comment'>-- This is easily fixed:</span>
<a name="line-697"></a><span class='hs-comment'>--</span>
<a name="line-698"></a><span class='hs-comment'>-- &gt; query conn "select ? + ?" (40 :: Double, 2 :: Double)</span>
<a name="line-699"></a><span class='hs-comment'>--</span>
<a name="line-700"></a><span class='hs-comment'>-- The same kind of problem can arise with string literals if you have</span>
<a name="line-701"></a><span class='hs-comment'>-- the @OverloadedStrings@ language extension enabled.  Again, just</span>
<a name="line-702"></a><span class='hs-comment'>-- use an explicit type signature if this happens.</span>
<a name="line-703"></a>
<a name="line-704"></a><span class='hs-comment'>-- $only_param</span>
<a name="line-705"></a><span class='hs-comment'>--</span>
<a name="line-706"></a><span class='hs-comment'>-- Haskell lacks a single-element tuple type, so if you have just one</span>
<a name="line-707"></a><span class='hs-comment'>-- value you want substituted into a query, what should you do?</span>
<a name="line-708"></a><span class='hs-comment'>--</span>
<a name="line-709"></a><span class='hs-comment'>-- The obvious approach would appear to be something like this:</span>
<a name="line-710"></a><span class='hs-comment'>--</span>
<a name="line-711"></a><span class='hs-comment'>-- &gt; instance (ToField a) =&gt; ToRow a where</span>
<a name="line-712"></a><span class='hs-comment'>-- &gt;     ...</span>
<a name="line-713"></a><span class='hs-comment'>--</span>
<a name="line-714"></a><span class='hs-comment'>-- Unfortunately, this wreaks havoc with type inference, so we take a</span>
<a name="line-715"></a><span class='hs-comment'>-- different tack. To represent a single value @val@ as a parameter, write</span>
<a name="line-716"></a><span class='hs-comment'>-- a singleton list @[val]@, use 'Just' @val@, or use 'Only' @val@.</span>
<a name="line-717"></a><span class='hs-comment'>--</span>
<a name="line-718"></a><span class='hs-comment'>-- Here's an example using a singleton list:</span>
<a name="line-719"></a><span class='hs-comment'>--</span>
<a name="line-720"></a><span class='hs-comment'>-- &gt; execute conn "insert into users (first_name) values (?)"</span>
<a name="line-721"></a><span class='hs-comment'>-- &gt;              ["Nuala"]</span>
<a name="line-722"></a>
<a name="line-723"></a><span class='hs-comment'>-- $in</span>
<a name="line-724"></a><span class='hs-comment'>--</span>
<a name="line-725"></a><span class='hs-comment'>-- Suppose you want to write a query using an @IN@ clause:</span>
<a name="line-726"></a><span class='hs-comment'>--</span>
<a name="line-727"></a><span class='hs-comment'>-- &gt; select * from users where first_name in ('Anna', 'Boris', 'Carla')</span>
<a name="line-728"></a><span class='hs-comment'>--</span>
<a name="line-729"></a><span class='hs-comment'>-- In such cases, it's common for both the elements and length of the</span>
<a name="line-730"></a><span class='hs-comment'>-- list after the @IN@ keyword to vary from query to query.</span>
<a name="line-731"></a><span class='hs-comment'>--</span>
<a name="line-732"></a><span class='hs-comment'>-- To address this case, use the 'In' type wrapper, and use a single</span>
<a name="line-733"></a><span class='hs-comment'>-- \"@?@\" character to represent the list.  Omit the parentheses</span>
<a name="line-734"></a><span class='hs-comment'>-- around the list; these will be added for you.</span>
<a name="line-735"></a><span class='hs-comment'>--</span>
<a name="line-736"></a><span class='hs-comment'>-- Here's an example:</span>
<a name="line-737"></a><span class='hs-comment'>--</span>
<a name="line-738"></a><span class='hs-comment'>-- &gt; query conn "select * from users where first_name in ?" $</span>
<a name="line-739"></a><span class='hs-comment'>-- &gt;       In ["Anna", "Boris", "Carla"]</span>
<a name="line-740"></a><span class='hs-comment'>--</span>
<a name="line-741"></a><span class='hs-comment'>-- If your 'In'-wrapped list is empty, the string @\"(null)\"@ will be</span>
<a name="line-742"></a><span class='hs-comment'>-- substituted instead, to ensure that your clause remains</span>
<a name="line-743"></a><span class='hs-comment'>-- syntactically valid.</span>
<a name="line-744"></a>
<a name="line-745"></a><span class='hs-comment'>-- $many</span>
<a name="line-746"></a><span class='hs-comment'>--</span>
<a name="line-747"></a><span class='hs-comment'>-- If you know that you have many rows of data to insert into a table,</span>
<a name="line-748"></a><span class='hs-comment'>-- it is much more efficient to perform all the insertions in a single</span>
<a name="line-749"></a><span class='hs-comment'>-- multi-row @INSERT@ statement than individually.</span>
<a name="line-750"></a><span class='hs-comment'>--</span>
<a name="line-751"></a><span class='hs-comment'>-- The 'executeMany' function is intended specifically for helping</span>
<a name="line-752"></a><span class='hs-comment'>-- with multi-row @INSERT@ and @UPDATE@ statements. Its rules for</span>
<a name="line-753"></a><span class='hs-comment'>-- query substitution are different than those for 'execute'.</span>
<a name="line-754"></a><span class='hs-comment'>--</span>
<a name="line-755"></a><span class='hs-comment'>-- What 'executeMany' searches for in your 'Query' template is a</span>
<a name="line-756"></a><span class='hs-comment'>-- single substring of the form:</span>
<a name="line-757"></a><span class='hs-comment'>--</span>
<a name="line-758"></a><span class='hs-comment'>-- &gt; values (?,?,?)</span>
<a name="line-759"></a><span class='hs-comment'>--</span>
<a name="line-760"></a><span class='hs-comment'>-- The rules are as follows:</span>
<a name="line-761"></a><span class='hs-comment'>--</span>
<a name="line-762"></a><span class='hs-comment'>-- * The keyword @VALUES@ is matched case insensitively.</span>
<a name="line-763"></a><span class='hs-comment'>--</span>
<a name="line-764"></a><span class='hs-comment'>-- * There must be no other \"@?@\" characters anywhere in your</span>
<a name="line-765"></a><span class='hs-comment'>--   template.</span>
<a name="line-766"></a><span class='hs-comment'>--</span>
<a name="line-767"></a><span class='hs-comment'>-- * There must be one or more \"@?@\" in the parentheses.</span>
<a name="line-768"></a><span class='hs-comment'>--</span>
<a name="line-769"></a><span class='hs-comment'>-- * Extra white space is fine.</span>
<a name="line-770"></a><span class='hs-comment'>--</span>
<a name="line-771"></a><span class='hs-comment'>-- The last argument to 'executeMany' is a list of parameter</span>
<a name="line-772"></a><span class='hs-comment'>-- tuples. These will be substituted into the query where the @(?,?)@</span>
<a name="line-773"></a><span class='hs-comment'>-- string appears, in a form suitable for use in a multi-row @INSERT@</span>
<a name="line-774"></a><span class='hs-comment'>-- or @UPDATE@.</span>
<a name="line-775"></a><span class='hs-comment'>--</span>
<a name="line-776"></a><span class='hs-comment'>-- Here is an example:</span>
<a name="line-777"></a><span class='hs-comment'>--</span>
<a name="line-778"></a><span class='hs-comment'>-- &gt; executeMany conn</span>
<a name="line-779"></a><span class='hs-comment'>-- &gt;   "insert into users (first_name,last_name) values (?,?)"</span>
<a name="line-780"></a><span class='hs-comment'>-- &gt;   [("Boris","Karloff"),("Ed","Wood")]</span>
<a name="line-781"></a><span class='hs-comment'>--</span>
<a name="line-782"></a><span class='hs-comment'>-- The query that will be executed here will look like this</span>
<a name="line-783"></a><span class='hs-comment'>-- (reformatted for tidiness):</span>
<a name="line-784"></a><span class='hs-comment'>--</span>
<a name="line-785"></a><span class='hs-comment'>-- &gt; insert into users (first_name,last_name) values</span>
<a name="line-786"></a><span class='hs-comment'>-- &gt;   ('Boris','Karloff'),('Ed','Wood')</span>
<a name="line-787"></a>
<a name="line-788"></a><span class='hs-comment'>-- $returning</span>
<a name="line-789"></a><span class='hs-comment'>--</span>
<a name="line-790"></a><span class='hs-comment'>-- PostgreSQL supports returning values from data manipulation statements</span>
<a name="line-791"></a><span class='hs-comment'>-- such as @INSERT@ and @UPDATE@.   You can use these statements by</span>
<a name="line-792"></a><span class='hs-comment'>-- using 'query' instead of 'execute'.   For multi-tuple inserts,</span>
<a name="line-793"></a><span class='hs-comment'>-- use 'returning' instead of 'executeMany'.</span>
<a name="line-794"></a><span class='hs-comment'>--</span>
<a name="line-795"></a><span class='hs-comment'>-- For example, were there an auto-incrementing @id@ column and</span>
<a name="line-796"></a><span class='hs-comment'>-- timestamp column @t@ that defaulted to the present time for the</span>
<a name="line-797"></a><span class='hs-comment'>-- @sales@ table, then the following query would insert two new</span>
<a name="line-798"></a><span class='hs-comment'>-- sales records and also return their new @id@s and timestamps.</span>
<a name="line-799"></a><span class='hs-comment'>--</span>
<a name="line-800"></a><span class='hs-comment'>-- &gt; let q = "insert into sales (amount, label) values (?,?) returning id, t"</span>
<a name="line-801"></a><span class='hs-comment'>-- &gt; xs :: [(Int, UTCTime)] &lt;- query conn q (15,"Sawdust")</span>
<a name="line-802"></a><span class='hs-comment'>-- &gt; ys :: [(Int, UTCTime)] &lt;- returning conn q [(20,"Chips"),(300,"Wood")]</span>
<a name="line-803"></a>
<a name="line-804"></a><span class='hs-comment'>-- $result</span>
<a name="line-805"></a><span class='hs-comment'>--</span>
<a name="line-806"></a><span class='hs-comment'>-- The 'query' and 'query_' functions return a list of values in the</span>
<a name="line-807"></a><span class='hs-comment'>-- 'FromRow' typeclass. This class performs automatic extraction</span>
<a name="line-808"></a><span class='hs-comment'>-- and type conversion of rows from a query result.</span>
<a name="line-809"></a><span class='hs-comment'>--</span>
<a name="line-810"></a><span class='hs-comment'>-- Here is a simple example of how to extract results:</span>
<a name="line-811"></a><span class='hs-comment'>--</span>
<a name="line-812"></a><span class='hs-comment'>-- &gt; import qualified Data.Text as Text</span>
<a name="line-813"></a><span class='hs-comment'>-- &gt;</span>
<a name="line-814"></a><span class='hs-comment'>-- &gt; xs &lt;- query_ conn "select name,age from users"</span>
<a name="line-815"></a><span class='hs-comment'>-- &gt; forM_ xs $ \(name,age) -&gt;</span>
<a name="line-816"></a><span class='hs-comment'>-- &gt;   putStrLn $ Text.unpack name ++ " is " ++ show (age :: Int)</span>
<a name="line-817"></a><span class='hs-comment'>--</span>
<a name="line-818"></a><span class='hs-comment'>-- Notice two important details about this code:</span>
<a name="line-819"></a><span class='hs-comment'>--</span>
<a name="line-820"></a><span class='hs-comment'>-- * The number of columns we ask for in the query template must</span>
<a name="line-821"></a><span class='hs-comment'>--   exactly match the number of elements we specify in a row of the</span>
<a name="line-822"></a><span class='hs-comment'>--   result tuple.  If they do not match, a 'ResultError' exception</span>
<a name="line-823"></a><span class='hs-comment'>--   will be thrown.</span>
<a name="line-824"></a><span class='hs-comment'>--</span>
<a name="line-825"></a><span class='hs-comment'>-- * Sometimes, the compiler needs our help in specifying types. It</span>
<a name="line-826"></a><span class='hs-comment'>--   can infer that @name@ must be a 'Text', due to our use of the</span>
<a name="line-827"></a><span class='hs-comment'>--   @unpack@ function. However, we have to tell it the type of @age@,</span>
<a name="line-828"></a><span class='hs-comment'>--   as it has no other information to determine the exact type.</span>
<a name="line-829"></a>
<a name="line-830"></a><span class='hs-comment'>-- $null</span>
<a name="line-831"></a><span class='hs-comment'>--</span>
<a name="line-832"></a><span class='hs-comment'>-- The type of a result tuple will look something like this:</span>
<a name="line-833"></a><span class='hs-comment'>--</span>
<a name="line-834"></a><span class='hs-comment'>-- &gt; (Text, Int, Int)</span>
<a name="line-835"></a><span class='hs-comment'>--</span>
<a name="line-836"></a><span class='hs-comment'>-- Although SQL can accommodate @NULL@ as a value for any of these</span>
<a name="line-837"></a><span class='hs-comment'>-- types, Haskell cannot. If your result contains columns that may be</span>
<a name="line-838"></a><span class='hs-comment'>-- @NULL@, be sure that you use 'Maybe' in those positions of your</span>
<a name="line-839"></a><span class='hs-comment'>-- tuple.</span>
<a name="line-840"></a><span class='hs-comment'>--</span>
<a name="line-841"></a><span class='hs-comment'>-- &gt; (Text, Maybe Int, Int)</span>
<a name="line-842"></a><span class='hs-comment'>--</span>
<a name="line-843"></a><span class='hs-comment'>-- If 'query' encounters a @NULL@ in a row where the corresponding</span>
<a name="line-844"></a><span class='hs-comment'>-- Haskell type is not 'Maybe', it will throw a 'ResultError'</span>
<a name="line-845"></a><span class='hs-comment'>-- exception.</span>
<a name="line-846"></a>
<a name="line-847"></a><span class='hs-comment'>-- $only_result</span>
<a name="line-848"></a><span class='hs-comment'>--</span>
<a name="line-849"></a><span class='hs-comment'>-- To specify that a query returns a single-column result, use the</span>
<a name="line-850"></a><span class='hs-comment'>-- 'Only' type.</span>
<a name="line-851"></a><span class='hs-comment'>--</span>
<a name="line-852"></a><span class='hs-comment'>-- &gt; xs &lt;- query_ conn "select id from users"</span>
<a name="line-853"></a><span class='hs-comment'>-- &gt; forM_ xs $ \(Only dbid) -&gt; {- ... -}</span>
<a name="line-854"></a>
<a name="line-855"></a><span class='hs-comment'>-- $types</span>
<a name="line-856"></a><span class='hs-comment'>--</span>
<a name="line-857"></a><span class='hs-comment'>-- Conversion of SQL values to Haskell values is somewhat</span>
<a name="line-858"></a><span class='hs-comment'>-- permissive. Here are the rules.</span>
<a name="line-859"></a><span class='hs-comment'>--</span>
<a name="line-860"></a><span class='hs-comment'>-- * For numeric types, any Haskell type that can accurately represent</span>
<a name="line-861"></a><span class='hs-comment'>--   all values of the given PostgreSQL type is considered \"compatible\".</span>
<a name="line-862"></a><span class='hs-comment'>--   For instance, you can always extract a PostgreSQL 16-bit @SMALLINT@</span>
<a name="line-863"></a><span class='hs-comment'>--   column to a Haskell 'Int'.  The Haskell 'Float' type can accurately</span>
<a name="line-864"></a><span class='hs-comment'>--   represent a @SMALLINT@, so it is considered compatble with those types.</span>
<a name="line-865"></a><span class='hs-comment'>--</span>
<a name="line-866"></a><span class='hs-comment'>-- * A numeric compatibility check is based only on the type of a</span>
<a name="line-867"></a><span class='hs-comment'>--   column, /not/ on its values. For instance, a PostgreSQL 64-bit</span>
<a name="line-868"></a><span class='hs-comment'>--   @BIGINT@ column will be considered incompatible with a Haskell</span>
<a name="line-869"></a><span class='hs-comment'>--   'Int16', even if it contains the value @1@.</span>
<a name="line-870"></a><span class='hs-comment'>--</span>
<a name="line-871"></a><span class='hs-comment'>-- * If a numeric incompatibility is found, 'query' will throw a</span>
<a name="line-872"></a><span class='hs-comment'>--   'ResultError'.</span>
<a name="line-873"></a><span class='hs-comment'>--</span>
<a name="line-874"></a><span class='hs-comment'>-- * The 'String' and 'Text' types are assumed to be encoded as</span>
<a name="line-875"></a><span class='hs-comment'>--   UTF-8. If you use some other encoding, decoding may fail or give</span>
<a name="line-876"></a><span class='hs-comment'>--   wrong results. In such cases, write a @newtype@ wrapper and a</span>
<a name="line-877"></a><span class='hs-comment'>--   custom 'Result' instance to handle your encoding.</span>
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