| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Dmitriy Sarafannikov <dsarafannikov(at)yandex(dot)ru> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Borodin Vladimir <root(at)simply(dot)name>, Хомик Кирилл <khomikki(at)yandex-team(dot)ru> |
| Subject: | Re: [PROPOSAL] Use SnapshotAny in get_actual_variable_range |
| Date: | 2017-05-08 13:47:04 |
| Message-ID: | CAA4eK1K6c=B3E_JoS+WafiiJiA2g-rKab4Y5nyB+j=7jiMH_RA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, May 8, 2017 at 6:30 PM, Dmitriy Sarafannikov
<dsarafannikov(at)yandex(dot)ru> wrote:
>
> 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).
>
>
> I took check from heap_page_prune_opt (Maybe this check must be present as
> separate function?)
> But it requires to initialize snapshot for specific relation.
>
+ else \
+ (snapshotdata).xmin = \
+ TransactionIdLimitedForOldSnapshots(RecentGlobalDataXmin, \
+ relation); \
I think we don't need to use TransactionIdLimitedForOldSnapshots() as
that is required to override xmin for table vacuum/pruning purposes.
> Maybe we need
> to use GetOldestXmin()?
It is a costly call as it needs ProcArrayLock, so I don't think it
makes sense to use it here.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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