On Wed, Jan 26, 2022 at 05:30:01PM -0800, Ben Chobot wrote: > We do a lot of queries per day, over a lot of hosts, all of which are on > 12.9. We've recently started doing a better job at analyzing our db logs and > have found that, a few times a day, every day, we see some of our queries > fail with errors like: > > could not open relation with OID 201940279 > > In the cases we've examined so far, the failed query succeeds just fine when > we run it manually. The failed query also had run on an async streaming > replica, and the primary has completed at least one autovacuum since the > failure. I don't know if either of those two facts are relevant, but I'm not > sure what else to blame. The internet seems to want to blame issues like > this on temp tables, which makes sense, but in our case, most of the queries > that are failing this way are simple PK scans, which then fall back to the > table to pull all the columns. The tables themselves are small in row count > - although some values are likely TOASTed - so I would be surprised if > anything is spilling to disk for sorting, which might have counted as a temp > table enough to give such an error. Do those OIDs point to some specific relations? It should be easy enough to guess to which pg_class entry they point to, especially if you have a persistent schema, and it these are indeed temporary entries or not depending on their pg_class.relnamespace. > This is a minuscule failure percentage, so replicating it is going to be > hard, but it is still breaking for reasons I don't understand, and so I'd > like to fix it. Has anybody else seen this, or have an ideas of what to look > at? I don't recall seeing such reports recently. > Other things we've considered: > - we run pg_repack, which certainly seems like it could make an error > like this, but we see this error in places and times that pg_repack isn't > currently running It could also take time for the issue to show up, depending on the state of the relcache. -- Michael
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