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: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Michael Paquier <michael@paquier.xyz>, "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-12-28T16:35:39Z
Lists: pgsql-hackers 
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> On 2018-Dec-28, Alvaro Herrera wrote:
>> On 2018-Dec-28, Michael Paquier wrote:
>>> There are many exotic extensions which could be using sizeof(PGPROC)
>>> as that's a popular structure,

>> Can you show one instance of this?

> I looked at 
> https://github.com/postgrespro/pg_wait_sampling/blob/master/pg_wait_sampling.c
> https://github.com/citusdata/citus/search?q=pgproc&unscoped_q=pgproc
> and skimmed a few others can't find any instance where the full struct
> is used, as opposed to just a pointer to it.

No, the point Michael is making is that the array stride in the ProcArray
is part of our ABI.  For example, accessing a PGPROC from its pgprocno
using the GetPGProcByNumber macro will be broken if we change the
struct size.  I do not think you can assume that no extension does that.

			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.