From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
---|---|
To: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Locking considerations of REINDEX |
Date: | 2018-07-04 15:01:08 |
Message-ID: | CAH2-Wzk8AY82wuV1Rkcj29AU11=JHeBV1Yd4foxH=hWizChbFw@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, Jul 4, 2018 at 5:08 AM, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> wrote:
> But AFAICS get_relation_info() tries to lock every index and since REINDEX
> will be holding a AEL on the index being reindexed, get_relation_info()
> blocks. Since get_relation_info() gets into every read path, wouldn't a
> concurrent REINDEX pretty much block every read access to the table, even if
> REINDEX not holding AEL on the table itself?
Not necessarily -- prepared statements may not block.
> I wonder if we just need fix the docs to or if we actually regressed at some
> point in the history or if we have a bug in the implementation? It mostly
> seems like a case of wrongly written docs even though in theory it might be
> possible to skip an index being rebuilt.
I still agree with this, though. The practical distinction between
getting an AEL on the table and what REINDEX does is pretty much
indistinguishable from zero.
--
Peter Geoghegan
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