Psycopg 2.4.2 released
Posted by Daniele Varrazzo on 2011-06-12
Tagged as news, release
Psycopg 2.4.2 has been released: it brings a few small but interesting new features, and a lot of bug fixes.
Transaction control has been overhauled: a new connection method set_session() allows setting all the session properties affecting the transactions behaviour: the isolation level but it can also be used to have auto-commit, read-only, and deferrable transactions. You can use for example:
conn.set_session('read committed') conn.set_session(readonly=True, autocommit=True) conn.set_session('serializable', readonly=True, deferrable=True)
There is also a welcome improvement for all the users thinking that
was an excessively verbose syntax: a new read/write property allows to set
conn.autocommit = True
a much handier syntax for an often used connection property.
The improvements to the transactions control are not only at interface level: Psycopg doesn't require any more setup queries when connecting to a database. A sequence of statements:
import psycopg2 conn = psycopg2.connect('') curs = conn.cursor() curs.execute('SELECT 1') curs.execute('SELECT 2') conn.commit()
in older versions of the library would have resulted in the following commands sent to the backend:
SHOW default_transaction_isolation SET DATESTYLE TO 'ISO' SHOW client_encoding BEGIN; SET TRANSACTION ISOLATION LEVEL READ COMMITTED SELECT 1 SELECT 2 COMMIT
In Psycopg 2.4.2 the only commands sent are instead the essential:
BEGIN SELECT 1 SELECT 2 COMMIT
with the BEGIN/COMMIT obviously omitted in autocommit mode (the datestyle and encoding statements were already dropped in 2.3).
The new release also brings a lot of bug fixes, so we encourage updating soon, particularly if you use Psycopg in multithread programs:
- Fixed bug with multithread code potentially causing loss of sync with the server communication or lock of the client (ticket #55).
- Don't fail import if mx.DateTime module can't be found, even if its support was built (ticket #53): a fix for the "ghost mx.DateTime" issue reported in virtualenv.
- Fixed escape for negative numbers prefixed by minus operator (ticket #57).
- Fixed GC race condition during copy in multithread programs, potentially resulting in refcount errors. Fixed by Dave Malcolm (ticket #58, Red Hat Bug 711095).
- Trying to execute concurrent operations on the same connection through concurrent green thread results in an error instead of a deadlock.
- Fixed detection of pg_config on Windows. Report and fix, plus some long needed setup.py cleanup by Steve Lacy: thanks!