at work at my company I inherited responsibility for a large PG 8.1 DB, with a an extreme number of tables (~300000). Surprisingly this is working quite well, except for maintenance and backup. I am tasked with finding a way to do dump & restore to 9.3 with as little downtime as possible.
Using 9.3's pg_dump with -j12 I found out that pg_dump takes 6 hours to lock tables using a single thread, then does the data dump in 1 more hour using 12 workers. However if I patch out the explicit LOCK TABLE statements this only takes 1 hour total. Of course no one else is using the DB at this time. In a pathological test case scenario in a staging environment the dump time decreased from 5 hours to 5 minutes.
I've googled the problem and there seem to be more people with similar problems, so I made this a command line option --no-table-locks and wrapped it up in as nice a patch against github/master as I can manage (and I didn't use C for a long time). I hope you find it useful.
Joe Conway sent me a tip so commit eeb6f37d89fc60c6449ca12ef9e914
91069369cb significantly decrease a time necessary for locking. So it can help to.
I am not sure, if missing lock is fully correct. In same situation I though about some form of database level lock. So you can get a protected access by one statement.
