On 2012-10-05 19:56:40 -0400, Tom Lane wrote: > 1. These operations think they can use ordinary heap_update operations > to change pg_index entries when they don't have exclusive lock on the > parent table. The lack of ex-lock means that another backend could be > currently loading up its list of index OIDs for the table --- and since > it scans pg_index with SnapshotNow to do that, the heap_update could > result in the other backend failing to see this index *at all*. That's > okay if it causes the other backend to not use the index for scanning... > but not okay if it causes the other backend to fail to make index > entries it is supposed to make. > > I think this could possibly be fixed by using nontransactional > update-in-place when we're trying to change indisvalid and/or > indisready, but I've not really thought through the details.
I couldn't really think of any realistic method to fix this other than update in place. I thought about it for a while and I think it should work, but I have to say it makes me slightly uneasy. If we could could ensure both land on the same page it would be possible to fix in a nicer way, but thats not really possible. Especially not in any way thats backpatchable. Unless somebody has a better idea I am going to write a patch for that. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
