Horton

Re: [PROPOSAL] Use SnapshotAny in get_actual_variable_range

Amit Kapila <amit.kapila16@gmail.com>

View thread View on postgr.es
From: Amit Kapila <amit.kapila16@gmail.com>
To: Dmitriy Sarafannikov <dsarafannikov@yandex.ru>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Borodin Vladimir <root@simply.name>, Хомик Кирилл <khomikki@yandex-team.ru>
Date: 2017-05-06T12:02:10Z
Lists: pgsql-hackers 
On Fri, May 5, 2017 at 1:28 PM, Dmitriy Sarafannikov
<dsarafannikov@yandex.ru> wrote:
> Amit, thanks for comments!
>
>> 1.
>> +#define InitNonVacuumableSnapshot(snapshotdata)  \
>> + do { \
>> + (snapshotdata).satisfies = HeapTupleSatisfiesNonVacuumable; \
>> + (snapshotdata).xmin = RecentGlobalDataXmin; \
>> + } while(0)
>> +
>>
>> Can you explain and add comments why you think RecentGlobalDataXmin is
>> the right to use it here?  As of now, it seems to be only used for
>> pruning non-catalog tables.
>
> Can you explain me, what value for xmin should be used there?
>

I think we can use RecentGlobalDataXmin for non-catalog relations and
RecentGlobalXmin for catalog relations (probably a check similar to
what we have in heap_page_prune_opt).


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Improve performance of get_actual_variable_range with recently-dead tuples.

  2. Use SnapshotDirty rather than an active snapshot to probe index endpoints.