Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Regarding sync commits that previously happen and now won't, I think the
> > only case worth worrying about is the one in vacuum.c. Do we need a
> > ForceSyncCommit() in there? I'm not sure if vacuum itself already
> > forces sync commit.
>
> Hmm, I had been assuming we wouldn't need that anymore.
The comment in user.c and dbcommands.c says
/* * Force synchronous commit, thus minimizing the window between * creation of the database files and
commitalof the transaction. If * we crash before committing, we'll have a DB that's taking up disk * space but
isnot in pg_database, which is not good. */ ForceSyncCommit();
so I think those ones are still necessary. There's another call in
RenameDatabase() which I don't think needs a sync commit (because it
won't change the dir name), and one in vacuum.c:
/*
! * If we were able to advance datfrozenxid, mark the flat-file copy of
! * pg_database for update at commit, and see if we can truncate pg_clog.
! * Also force update if the shared XID-wrap-limit info is stale. */ if (dirty ||
!TransactionIdLimitIsValid())
- {
- database_file_update_needed(); vac_truncate_clog(newFrozenXid);
- } }
AFAICT this doesn't need a sync commit. (Right now, VACUUM FULL forces
one, but lazy vacuum doesn't).
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
