* Tom Lane (t...@sss.pgh.pa.us) wrote: > Stephen Frost <sfr...@snowman.net> writes: > > I don't have too much of an issue with the above, but I would like to > > have us figure out a solution to the deadlock problem with parallel > > pg_dump. The issue arises when pg_dump gets an AccessShareLock and then > > another process attempts to acquire an AccessExclusiveLock, which then > > blocks, and then the pg_dump worker process tries to get its > > AccessShareLock- we end up not being able to make any progress on > > anything at that point. > > The original ASL was acquired by the pg_dump master, right?
Yup. It goes through and gets ASLs on everything first.
> > One suggestion that was discussed at PGConf.EU was having processes
> > which share the same snapshot (the pg_dump master and worker processes)
> > able to either share the same locks or at least be able to "jump" the
> > lock queue (that is, the worker process wouldn't have to wait being the
> > AEL to get an ASL, since the ASL was already aquired for the snapshot
> > which was exported and shared with it).
>
> Yeah, it seems like we need lock export not only snapshot export to make
> this work nicely. But that sounds orthogonal to the issues being
> discussed in this thread.
Indeed, just figured I'd mention it since we're talking about
pg_dump-related locking.
Thanks,
Stephen
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