From: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
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To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: old_snapshot_threshold's interaction with hash index |
Date: | 2016-05-02 21:02:35 |
Message-ID: | CACjxUsOEoqTF7SsTAozW0Y6qRX7HhiCQ=na5tVfeCnsmNcRR_A@mail.gmail.com |
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Lists: | pgsql-hackers |
On Sun, May 1, 2016 at 1:43 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Sun, May 1, 2016 at 12:05 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>
>> Currently we do the test for old snapshot (TestForOldSnapshot) for hash
>> indexes while scanning them. Does this test makes any sense for hash
>> indexes considering LSN on hash index will always be zero (as hash indexes
>> are not WAL-logged)? It seems to me that PageLSN check in
>> TestForOldSnapshot() will always return false which means that the error
>> "snapshot too old" won't be generated for hash indexes.
>>
>> Am I missing something here, if not, then I think we need a way to
>> prohibit pruning for hash indexes based on old_snapshot_threshold?
>
> What I mean to say here is prohibit pruning the relation which has hash
> index based on old_snapshot_threshold.
Good spot; added to the open issues page.
Thanks!
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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