Horton

Re: pg_restore causing deadlocks on partitioned tables

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Amit Langote <amitlangote09@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Domagoj Smoljanovic <domagoj.smoljanovic@oradian.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-09-15T13:47:31Z
Lists: pgsql-hackers 
Amit Langote <amitlangote09@gmail.com> writes:
> On Tue, Sep 15, 2020 at 9:09 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I wrote a quick patch for this part.  It seems pretty safe and probably
>> could be back-patched without fear.

> The patch's theory that if the parent column has NOT NULL set then it
> must be set in child tables too does not actually hold for plain
> inheritance cases, because as shown above, NOT NULL can be dropped in
> children independently of the parent.

Ah, right.  That seems like a bug but we have not attempted to fix it.
But we could restrict the optimization to partitioned tables, where
the assumption does hold, no?

			regards, tom lane

Commits

  1. Don't fetch partition check expression during InitResultRelInfo.

  2. Avoid unnecessary recursion to child tables in ALTER TABLE SET NOT NULL.