Horton

Re: buildfarm: could not read block 3 in file "base/16384/2662": read only 0 of 8192 bytes

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-08-29T16:56:07Z
Lists: pgsql-hackers 
I wrote:
> * We now recursively enter ScanPgRelation, which (again) needs to do a
> search using pg_class_oid_index, so it (again) opens and locks that.
> BUT: LockRelationOid sees that *this process already has share lock on
> pg_class_oid_index*, so it figures it can skip AcceptInvalidationMessages.

BTW, I now have a theory for why we suddenly started seeing this problem
in mid-June: commits a54e1f158 et al added a ScanPgRelation call where
there had been none before (in RelationReloadNailed, for non-index rels).
That didn't create the problem, but it probably increased the odds of
seeing it happen.

Also ... isn't the last "relation->rd_isvalid = true" in
RelationReloadNailed wrong?  If it got cleared during ScanPgRelation,
I do not think we want to believe that we got an up-to-date row.

			regards, tom lane

Commits

  1. Limit depth of forced recursion for CLOBBER_CACHE_RECURSIVELY.

  2. Fix longstanding recursion hazard in sinval message processing.

  3. Fix bugs in vacuum of shared rels, by keeping their relcache entries current.