postrm is in odbc-postgresql 1:09.03.0300-1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | #!/bin/sh
set -e
case $1 in
	remove)
		if test -x /usr/bin/odbcinst ; then
			odbcinst -u -d -n 'PostgreSQL ANSI'
			odbcinst -u -d -n 'PostgreSQL Unicode'
		fi ;;
esac
 |