We have an issue
with running pg_dump while a database is under reasonably heavy update load.
This is 7.4.5 on Solaris 9/intel.
The observed
behavior was that a pg_dump running with nothing else going on takes a couple of
minutes, but when we are running some system tests that do heavy updates to a
selection of application tables, it appears that pg_dump blocks until the update
run is done. This didn't make sense because everything I can find about pg_dump
indicates that it should only be taking read locks, so I don't see why it should
be blocked.
We looked at
pg_locks, and saw that the pg_dump process was acquiring locks
like:
14764 |
ExclusiveLock | 124576072 | COPY public.stats (id, description,
lastsavedate, lastsaveuser) TO stdout;
(we are using
pg_dump with -Fc) If COPY is taking a ROW EXCLUSIVE lock, then that would
explain why we are seeing contention, but I don't understand why COPY is locking
at that level. Is there a better way to run pg_dump against a database with a
lot of update activity?
Thanks.
- DAP
======================================================
David Parker Tazz
Networks
