On Wed, Sep 23, 2015 at 1:41 PM, Jim Nasby <jim.na...@bluetreble.com> wrote: > max was set to 10000. I don't know about average query text size, but the > command that was causing the error was a very large number of individual > INSERT ... VALUES statements all in one command. > > The machine had plenty of free memory and no ulimit, so I don't see how this > could have been anything but MaxAllocSize, unless there's some other failure > mode in malloc I don't know about.
The patch that Tom committed does __nothing__ to actually address *how* you were able to get into this position in the first place. Sure, now you might be able to recover if you're not affected by the MaxAllocSize limitation, but: What did it take in the first place to need memory > MaxAllocSize to do a garbage collection? Whatever it was that allowed things to get that bad before a garbage collection was attempted is not even considered in the patch committed. The patch just committed is, in short, nothing more than a band-aid, and may do more harm than good due to allocating huge amounts of memory while a very contended exclusive LWLock is held. You say you have plenty of memory and no ulimit, and I believe that you're right that there was never a conventional OOM where malloc() returns NULL. If we conservatively assume that you were only barely over the MaxAllocSize limitation before a garbage collection was first attempted, then the average query text length would have to be about 50 kilobytes, since only then 20,000 texts (pg_stat_statements.max * 2) would put us over. Does anyone actually think that the *average* SQL query on Jim's client's application was in excess of 50% the size of the ~3,000 line file pg_stat_statements.c? It beggars belief. I'm annoyed and disappointed that the patch committed does not even begin to address the underlying problem -- it just adds an escape hatch, and fixes another theoretical issue that no one was affected by. Honestly, next time I won't bother. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
