/usr/lib/perl5/DBI/DBD/SqlEngine/Developers.pod is in libdbi-perl 1.616-1build2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 | =head1 NAME
DBI::DBD::SqlEngine::Developers - Developers documentation for DBI::DBD::SqlEngine
=head1 SYNOPSIS
package DBD::myDriver;
use base qw(DBI::DBD::SqlEngine);
sub driver
{
...
my $drh = $proto->SUPER::driver($attr);
...
return $drh->{class};
}
sub CLONE { ... }
package DBD::myDriver::dr;
@ISA = qw(DBI::DBD::SqlEngine::dr);
sub data_sources { ... }
...
package DBD::myDriver::db;
@ISA = qw(DBI::DBD::SqlEngine::db);
sub init_valid_attributes { ... }
sub init_default_attributes { ... }
sub set_versions { ... }
sub validate_STORE_attr { my ($dbh, $attrib, $value) = @_; ... }
sub validate_FETCH_attr { my ($dbh, $attrib) = @_; ... }
sub get_myd_versions { ... }
sub get_avail_tables { ... }
package DBD::myDriver::st;
@ISA = qw(DBI::DBD::SqlEngine::st);
sub FETCH { ... }
sub STORE { ... }
package DBD::myDriver::Statement;
@ISA = qw(DBI::DBD::SqlEngine::Statement);
sub open_table { ... }
package DBD::myDriver::Table;
@ISA = qw(DBI::DBD::SqlEngine::Table);
sub new { ... }
sub fetch_row { ... }
sub push_row { ... }
sub push_names { ... }
sub seek { ... }
sub truncate { ... }
sub drop { ... }
# optimize the SQL engine by add one or more of
sub update_current_row { ... }
# or
sub update_specific_row { ... }
# or
sub update_one_row { ... }
# or
sub insert_new_row { ... }
# or
sub delete_current_row { ... }
# or
sub delete_one_row { ... }
=head1 DESCRIPTION
This document describes the interface of DBI::DBD::SqlEngine for DBD
developers who write DBI::DBD::SqlEngine based DBI drivers. It supplements
L<DBI::DBD> and L<DBI::DBD::SqlEngine::HowTo>, which you should read first.
=head1 CLASSES
Each DBI driver must provide a package global C<< driver >> method and
three DBI related classes:
=over 4
=item DBI::DBD::SqlEngine::dr
Driver package, contains the methods DBI calls indirectly via DBI
interface:
DBI->connect ('DBI:DBM:', undef, undef, {})
# invokes
package DBD::DBM::dr;
@DBD::DBM::dr::ISA = qw(DBI::DBD::SqlEngine::dr);
sub connect ($$;$$$)
{
...
}
Similar for C<< data_sources () >> and C<< disconnect_all() >>.
Pure Perl DBI drivers derived from DBI::DBD::SqlEngine do not usually need to
override any of the methods provided through the DBD::XXX::dr package
however if you need additional initialization in the connect method
you may need to.
=item DBI::DBD::SqlEngine::db
Contains the methods which are called through DBI database handles
(C<< $dbh >>). e.g.,
$sth = $dbh->prepare ("select * from foo");
# returns the f_encoding setting for table foo
$dbh->csv_get_meta ("foo", "f_encoding");
DBI::DBD::SqlEngine provides the typical methods required here. Developers who
write DBI drivers based on DBI::DBD::SqlEngine need to override the methods
C<< set_versions >> and C<< init_valid_attributes >>.
=item DBI::DBD::SqlEngine::st
Contains the methods to deal with prepared statement handles. e.g.,
$sth->execute () or die $sth->errstr;
=back
=head2 DBI::DBD::SqlEngine
This is the main package containing the routines to initialize
DBI::DBD::SqlEngine based DBI drivers. Primarily the
C<< DBI::DBD::SqlEngine::driver >> method is invoked, either directly
from DBI when the driver is initialized or from the derived class.
package DBD::DBM;
use base qw( DBI::DBD::SqlEngine );
sub driver
{
my ( $class, $attr ) = @_;
...
my $drh = $class->SUPER::driver( $attr );
...
return $drh;
}
It is not necessary to implement your own driver method as long as
additional initialization (e.g. installing more private driver
methods) is not required. You do not need to call C<< setup_driver >>
as DBI::DBD::SqlEngine takes care of it.
=head2 DBI::DBD::SqlEngine::dr
The driver package contains the methods DBI calls indirectly via the DBI
interface (see L<DBI/DBI Class Methods>).
DBI::DBD::SqlEngine based DBI drivers usually do not need to implement anything here,
it is enough to do the basic initialization:
package DBD:XXX::dr;
@DBD::XXX::dr::ISA = qw (DBI::DBD::SqlEngine::dr);
$DBD::XXX::dr::imp_data_size = 0;
$DBD::XXX::dr::data_sources_attr = undef;
$DBD::XXX::ATTRIBUTION = "DBD::XXX $DBD::XXX::VERSION by Hans Mustermann";
=head2 DBI::DBD::SqlEngine::db
This package defines the database methods, which are called via the DBI
database handle C<< $dbh >>.
Methods provided by DBI::DBD::SqlEngine:
=over 4
=item ping
Simply returns the content of the C<< Active >> attribute. Override
when your driver needs more complicated actions here.
=item prepare
Prepares a new SQL statement to execute. Returns a statement handle,
C<< $sth >> - instance of the DBD:XXX::st. It is neither required nor
recommended to override this method.
=item FETCH
Fetches an attribute of a DBI database object. Private handle attributes
must have a prefix (this is mandatory). If a requested attribute is
detected as a private attribute without a valid prefix, the driver prefix
(written as C<$drv_prefix>) is added.
The driver prefix is extracted from the attribute name and verified against
C<< $dbh->{ $drv_prefix . "valid_attrs" } >> (when it exists). If the
requested attribute value is not listed as a valid attribute, this method
croaks. If the attribute is valid and readonly (listed in C<< $dbh->{
$drv_prefix . "readonly_attrs" } >> when it exists), a real copy of the
attribute value is returned. So it's not possible to modify
C<f_valid_attrs> from outside of DBI::DBD::SqlEngine::db or a derived class.
=item STORE
Stores a database private attribute. Private handle attributes must have a
prefix (this is mandatory). If a requested attribute is detected as a private
attribute without a valid prefix, the driver prefix (written as
C<$drv_prefix>) is added. If the database handle has an attribute
C<${drv_prefix}_valid_attrs> - for attribute names which are not listed in
that hash, this method croaks. If the database handle has an attribute
C<${drv_prefix}_readonly_attrs>, only attributes which are not listed there
can be stored (once they are initialized). Trying to overwrite such an
immutable attribute forces this method to croak.
An example of a valid attributes list can be found in
C<< DBI::DBD::SqlEngine::db::init_valid_attributes >>.
=item set_versions
This method sets the attributes C<< f_version >>, C<< sql_nano_version >>,
C<< sql_statement_version >> and (if not prohibited by a restrictive
C<< ${prefix}_valid_attrs >>) C<< ${prefix}_version >>.
This method is called at the end of the C<< connect () >> phase.
When overriding this method, do not forget to invoke the superior one.
=item init_valid_attributes
This method is called after the database handle is instantiated as the
first attribute initialization.
C<< DBI::DBD::SqlEngine::db::init_valid_attributes >> initializes the
attributes C<sql_valid_attrs> and C<sql_readonly_attrs>.
When overriding this method, do not forget to invoke the superior one,
preferably before doing anything else.
=item init_default_attributes
This method is called after the database handle is instantiated to
initialize the default attributes.
C<< DBI::DBD::SqlEngine::db::init_default_attributes >> initializes the
attributes C<sql_identifier_case>, C<sql_quoted_identifier_case>,
C<sql_handler>, C<sql_engine_version>, C<sql_nano_version> and
C<sql_statement_version> when L<SQL::Statement> is available.
When the derived implementor class provides the attribute to validate
attributes (e.g. C<< $dbh->{dbm_valid_attrs} = {...}; >>) or the attribute
containing the immutable attributes (e.g. C<< $dbh->{dbm_readonly_attrs}
= {...}; >>), the attributes C<drv_valid_attrs>, C<drv_readonly_attrs> and
C<drv_version> are added (when available) to the list of valid and
immutable attributes (where C<drv_> is interpreted as the driver prefix).
=item get_versions
This method is called by the code injected into the instantiated driver to
provide the user callable driver method C<< ${prefix}versions >> (e.g.
C<< dbm_versions >>, C<< csv_versions >>, ...).
The DBI::DBD::SqlEngine implementation returns all version information known by
DBI::DBD::SqlEngine (e.g. DBI version, Perl version, DBI::DBD::SqlEngine version and
the SQL handler version).
C<get_versions> takes the C<$dbh> as the first argument and optionally a
second argument containing a table name. The second argument is not
evaluated in C<< DBI::DBD::SqlEngine::db::get_versions >> itself - but
might be in the future.
If the derived implementor class provides a method named
C<get_${drv_prefix}versions>, this is invoked and the return value of
it is associated to the derived driver name:
if (my $dgv = $dbh->{ImplementorClass}->can ("get_" . $drv_prefix . "versions") {
(my $derived_driver = $dbh->{ImplementorClass}) =~ s/::db$//;
$versions{$derived_driver} = &$dgv ($dbh, $table);
}
Override it to add more version information about your module, (e.g.
some kind of parser version in case of DBD::CSV, ...), if one line is not
enough room to provide all relevant information.
=item sql_parser_object
Returns a L<SQL::Parser> instance, when C<< sql_handler >> is set to
"SQL::Statement". The parser instance is stored in C<< sql_parser_object >>.
It is not recommended to override this method.
=item disconnect
Disconnects from a database. All local table information is discarded and
the C<< Active >> attribute is set to 0.
=item type_info_all
Returns information about all the types supported by DBI::DBD::SqlEngine.
=item table_info
Returns a statement handle which is prepared to deliver information about
all known tables.
=item list_tables
Returns a list of all known table names.
=item quote
Quotes a string for use in SQL statements.
=item commit
Warns about a useless call (if warnings enabled) and returns.
DBI::DBD::SqlEngine is typically a driver which commits every action instantly when
executed.
=item rollback
Warns about a useless call (if warnings enabled) and returns.
DBI::DBD::SqlEngine is typically a driver which commits every action instantly when
executed.
=back
=head2 DBI::DBD::SqlEngine::st
Contains the methods to deal with prepared statement handles:
=over 4
=item bind_param
Common routine to bind placeholders to a statement for execution. It
is dangerous to override this method without detailed knowledge about
the DBI::DBD::SqlEngine internal storage structure.
=item execute
Executes a previously prepared statement (with placeholders, if any).
=item finish
Finishes a statement handle, discards all buffered results. The prepared
statement is not discarded so the statement can be executed again.
=item fetch
Fetches the next row from the result-set. This method may be rewritten
in a later version and if it's overridden in a derived class, the
derived implementation should not rely on the storage details.
=item fetchrow_arrayref
Alias for C<< fetch >>.
=item FETCH
Fetches statement handle attributes. Supported attributes (for full overview
see L<DBI/Statement Handle Attributes>) are C<NAME>, C<TYPE>, C<PRECISION>
and C<NULLABLE>. Each column is returned as C<NULLABLE> which might be wrong
depending on the derived backend storage. If the statement handle has
private attributes, they can be fetched using this method, too. B<Note> that
statement attributes are not associated with any table used in this statement.
This method usually requires extending in a derived implementation.
See L<DBD::CSV> or L<DBD::DBM> for some example.
=item STORE
Allows storing of statement private attributes. No special handling is
currently implemented here.
=item rows
Returns the number of rows affected by the last execute. This method might
return C<undef>.
=back
=head2 DBI::DBD::SqlEngine::Statement
Derives from DBI::SQL::Nano::Statement for unified naming when deriving
new drivers. No additional feature is provided from here.
=head2 DBI::DBD::SqlEngine::Table
Derives from DBI::SQL::Nano::Table for unified naming when deriving
new drivers. No additional feature is provided from here.
You should consult the documentation of C<< SQL::Eval::Table >> (see
L<SQL::Eval>) to get more information about the abstract methods of the
table's base class you have to override and a description of the table
meta information expected by the SQL engines.
=head1 AUTHOR
The module DBI::DBD::SqlEngine is currently maintained by
H.Merijn Brand < h.m.brand at xs4all.nl > and
Jens Rehsack < rehsack at googlemail.com >
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2010 by H.Merijn Brand & Jens Rehsack
All rights reserved.
You may freely distribute and/or modify this module under the terms of
either the GNU General Public License (GPL) or the Artistic License, as
specified in the Perl README file.
=cut
|