typecast.py

# typecast.py - example of per-cursor and per-connection typecasters.
#
# Copyright (C) 2001-2010 Federico Di Gregorio  <fog@debian.org>
#
# psycopg2 is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
# License for more details.

## put in DSN your DSN string

DSN = 'dbname=test'

## don't modify anything below this line (except for experimenting)

class SimpleQuoter(object):
    def sqlquote(x=None):
        return "'bar'"

import sys
import psycopg2
import psycopg2.extensions

if len(sys.argv) > 1:
    DSN = sys.argv[1]

print "Opening connection using dsn:", DSN
conn = psycopg2.connect(DSN)
print "Encoding for this connection is", conn.encoding

curs = conn.cursor()
curs.execute("SELECT 'text'::text AS foo")
textoid = curs.description[0][1]
print "Oid for the text datatype is", textoid

def castA(s, curs):
    if s is not None: return "(A) " + s
TYPEA = psycopg2.extensions.new_type((textoid,), "TYPEA", castA)

def castB(s, curs):
    if s is not None: return "(B) " + s
TYPEB = psycopg2.extensions.new_type((textoid,), "TYPEB", castB)

curs = conn.cursor()
curs.execute("SELECT 'some text.'::text AS foo")
print "Some text from plain connection:", curs.fetchone()[0]

psycopg2.extensions.register_type(TYPEA, conn)
curs = conn.cursor()
curs.execute("SELECT 'some text.'::text AS foo")
print "Some text from connection with typecaster:", curs.fetchone()[0]

curs = conn.cursor()
psycopg2.extensions.register_type(TYPEB, curs)
curs.execute("SELECT 'some text.'::text AS foo")
print "Some text from cursor with typecaster:", curs.fetchone()[0]

curs = conn.cursor()
curs.execute("SELECT 'some text.'::text AS foo")
print "Some text from connection with typecaster again:", curs.fetchone()[0]