Horton

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

Asim Praveen <pasim@vmware.com>

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From: Asim Praveen <pasim@vmware.com>
To: Ashutosh Sharma <ashu.coek88@gmail.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: 2020-08-13T07:06:14Z
Lists: pgsql-hackers 
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;

Asim

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.