Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-09-01T00:21:01Z
Lists: pgsql-hackers 
Hi,

On 2018-08-31 19:53:43 -0400, Tom Lane wrote:
> My thought is to do (and back-patch) my change, and then work on yours
> as a performance improvement for HEAD only.

That does make sense.

> I don't believe that yours would make mine redundant, either --- they
> are good complementary changes to make real sure we have no remaining
> bugs of this ilk.  (In particular, no matter how much de-duplication
> we do, we'll still have scenarios with recursive cache flushes; so I'm
> not quite convinced that your solution provides a 100% fix by itself.)

Yea this is a fair concern.

One concern I have with your approach is that it isn't particularly
bullet-proof for cases where the rebuild is triggered by something that
doesn't hold a conflicting lock.  If there's an independent cause to
reload - something that very commonly happens - we might not necessarily
re-trigger the recursive reloads.  That *should* be safe due such
changes hopefully being "harmless", but it's a bit disconcerting
nonetheless.

Greetings,

Andres Freund

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.