From: Carwyn Edwards <cedward1@inf.ed.ac.uk>
To: pgsql-interfaces@postgresql.org
Cc: andre@via.ecp.fr
Cc: pgsql-admin@postgresql.org
Subject: Python DB-API problem with PostgresSQL pgdb.
Date: Mon, 27 Jan 2003 05:06:13 +0000
Message-ID: <3E34BE45.6010309@inf.ed.ac.uk> (raw)
The Python DB-API (2.0) specifies that on creation a connection object
is to start a transaction if the database supports them. The pgdb
implementation of the DB-API does this:
>>> Begin Listing 1
class pgdbCnx:
def __init__(self, cnx):
self.__cnx = cnx
self.__cache = pgdbTypeCache(cnx)
try:
src = self.__cnx.source()
src.execute("BEGIN")
except:
raise OperationalError, "invalid connection."
>>> End Listing 1
This is all well and good except there does not seem to be any way of
NOT starting a transaction block. This is a real problem if you are
trying to create admin scripts that automate database creation as CREATE
DATABASE in PostgreSQL can not be called from within a transaction
block. Listing 2 shows the raw SQL typed into psql that simulates what
happens from the pgdb module when you try and create a database:
>>> Begin Listing 2
cedward1=# begin;
BEGIN
cedward1=# create database thingy;
ERROR: CREATE DATABASE: may not be called in a transaction block
>>> End Listing 2
I'll let the experts argue as to whether this is a problem for Python's
DB-API or a PostgreSQL issue.
Carwyn
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To: pgsql-interfaces@postgresql.org
Cc: cedward1@inf.ed.ac.uk, andre@via.ecp.fr, pgsql-admin@postgresql.org
Subject: Re: Python DB-API problem with PostgresSQL pgdb.
In-Reply-To: <3E34BE45.6010309@inf.ed.ac.uk>
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