Horton

Re: removal of dangling temp tables

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-12-14T17:57:23Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> On Fri, Dec 14, 2018 at 11:29 AM Alvaro Herrera
> <alvherre@2ndquadrant.com> wrote:
>> I think the best way to fix this is to call RemoveTempRelations()
>> unconditionally at session start (without doing the rest of the temp
>> table setup, just the removal.)

> That would certainly simplify things.  I think I thought about that as
> far back as a734fd5d1c309cc553b7c8c79fba96218af090f7 but it seemed
> like a significant behavior change and I wasn't sure that everyone
> would like it.  In particular, it adds overhead to backend startup
> that, in the case of a large temp schema, could be fairly long.

> Nevertheless, I tentatively think that a change like this is a good
> idea.  I wouldn't back-patch it, though.

I seem to recall discussions about having crash recovery go around
and clean out temp tables.  That seems like a better plan than
penalizing every session start with this.

			regards, tom lane

Commits

  1. Have DISCARD ALL/TEMP remove leftover temp tables

  2. Make autovacuum more selective about temp tables to keep

  3. Make autovacuum more aggressive to remove orphaned temp tables

  4. autovacuum: Drop orphan temp tables more quickly but with more caution.