Horton

Re: recovering from "found xmin ... from before relfrozenxid ..."

Ashutosh Sharma <ashu.coek88@gmail.com>

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From: Ashutosh Sharma <ashu.coek88@gmail.com>
To: Asim Praveen <pasim@vmware.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Masahiko Sawada <masahiko.sawada@2ndquadrant.com>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, MBeena Emerson <mbeena.emerson@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Stephen Frost <sfrost@snowman.net>
Date: 2020-08-13T07:52:38Z
Lists: pgsql-hackers 
Hi Asim,

Thanks for having a look into the patch and for sharing your feedback.
Please find my comments inline below:

On Thu, Aug 13, 2020 at 12:36 PM Asim Praveen <pasim@vmware.com> wrote:
>
> Hi Ashutosh
>
> I stumbled upon this thread today, went through your patch and it looks good.  A minor suggestion in sanity_check_relation():
>
>         if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
>                 ereport(ERROR,
>                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>                                  errmsg("only heap AM is supported")));
>
> Instead of checking the access method OID, it seems better to check the handler OID like so:
>
>         if (rel->rd_amhandler != HEAP_TABLE_AM_HANDLER_OID)
>
> The reason is current version of sanity_check_relation() would emit error for the following case even when the table structure is actually heap.
>
>         create access method myam type table handler heap_tableam_handler;
>         create table mytable (…) using myam;
>

This looks like a very good suggestion to me. I will do this change in
the next version. Just wondering if we should be doing similar changes
in other contrib modules (like pgrowlocks, pageinspect and
pgstattuple) as well?

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com

Commits

  1. Fix wrong data table horizon computation during backend startup.

  2. Centralize horizon determination for temp tables, fixing bug due to skew.

  3. pg_surgery: Try to stabilize regression tests.

  4. New contrib module, pg_surgery, with heap surgery functions.

  5. Set cutoff xmin more aggressively when vacuuming a temporary table.

  6. snapshot scalability: Don't compute global horizons while building snapshots.

  7. Introduce vacuum errcontext to display additional information.