Last week we moved psycopg from Subversion to Bazaar. I did the migration using Gustavo Niemeyer's svn2bzr tool with a few tweaks to map the old Subversion committer IDs to the email address form conventionally used by Bazaar.

The tool does a good job of following tree copies and create related Bazaar branches. It doesn't have any special handling for stuff in the tags/ directory (it produces new branches, as it does for other tree copies). To get real Bazaar tags, I wrote a simple post-processing script to calculate the heads of all the branches in a tags/ directory and set them as tags in another branch (provided those revisions occur in its ancestry). This worked pretty well except for a few revisions synthesised by a previous cvs2svn migration. As these tags were from pretty old psycopg 1 releases I don't know how much it matters.

Yesterday Federico released version 2.0.7 of psycopg2 (a Python database adapter for PostgreSQL). I made a fair number of the changes in this release to make it more usable for some of Canonical's applications. The new release should work with the development version of Storm, and shouldn't be too difficult to get everything working with other frameworks.

Some of the improvements include:

• Better selection of exceptions based on the SQLSTATE result field. This causes a number of errors that were reported as ProgrammingError to use a more appropriate exception (e.g. DataError, OperationalError, InternalError). This was the change that broke Storm's test suite as it was checking for ProgrammingError on some queries that were clearly not programming errors.
• Proper error reporting for commit() and rollback(). These methods now use the same error reporting code paths as execute(), so an integrity error on commit() will now raise IntegrityError rather than OperationalError.
• The compile-time switch that controls whether the display_size member of Cursor.description is calculated is now turned off by default. The code was quite expensive and the field is of limited use (and not provided by a number of other database adapters).
• New QueryCanceledError and TransactionRollbackError exceptions. The first is useful for handling queries that are canceled by statement_timeout. The second provides a convenient way to catch serialisation failures and deadlocks: errors that indicate the transaction should be retried.
• Fixes for a few memory leaks and GIL misuses. One of the leaks was in the notice processing code that could be particularly problematic for long-running daemon processes.
• Better test coverage and a driver script to run the entire test suite in one go. The tests should all pass too, provided your database cluster uses unicode (there was a report just before the release of one test failing for a LATIN1 cluster).

If you're using previous versions of psycopg2, I'd highly recommend upgrading to this release.

Marc uploaded a new revision of the Python DB-API 2.0 Specification yesterday that documents the new two phase commit extension that I helped develop on the db-sig mailing list.

My interest in this started from the desire to support two phase commit in Storm – without that feature there are far fewer occasions where its ability to talk to multiple databases can be put to use. As I was doing some work on psycopg2 for Launchpad, I initially put together a PostgreSQL specific patch, which was (rightly) rejected by Federico.