Horton

Re: Bugs in TOAST handling, OID assignment and redo recovery

Pavan Deolasee <pavan.deolasee@gmail.com>

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From: Pavan Deolasee <pavan.deolasee@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-04-11T18:43:18Z
Lists: pgsql-hackers

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On Wed, Apr 11, 2018 at 8:20 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Pavan Deolasee <pavan.deolasee@gmail.com> writes:
> > Or may be we simply err on the side of caution and scan the toast table
> > with SnapshotAny while looking for a duplicate? That might prevent us
> from
> > reusing an OID for a known-dead tuple, but should save us a second index
> > scan and still work.
>
> +1.  We really don't want to expend two indexscans on this.
>
>
Ok. I propose attached patches, more polished this time. I also
changed toastrel_valueid_exists() to use SnapshotAny, but I don't have any
proofs to claim that's a needed change. But it seems harmless and given the
number of toast related, hard to chase bugs we have seen over the years,
may it's worth making it full proof too.

Thanks,
Pavan

-- 
 Pavan Deolasee                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Ignore nextOid when replaying an ONLINE checkpoint.

  2. Do not select new object OIDs that match recently-dead entries.