Re: DROP OWNED CASCADE vs Temp tables

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Mithun Cy <mithun(dot)cy(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: DROP OWNED CASCADE vs Temp tables
Date: 2020-01-23 17:14:23
Message-ID: 20200123171423.GA25918@alvherre.pgsql
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On 2020-Jan-14, Alvaro Herrera wrote:

> On 2020-Jan-13, Tom Lane wrote:
> > That seems fundamentally wrong. By the time we've queued an object for
> > deletion in dependency.c, we have a lock on it, and we've verified that
> > the object is still there (cf. systable_recheck_tuple calls).
> > If shdepDropOwned is doing it differently, I'd say shdepDropOwned is
> > doing it wrong.
> Hmm, it seems to be doing it differently. Maybe it should be acquiring
> locks on all objects in that nested loop and verified them for
> existence, so that when it calls performMultipleDeletions the objects
> are already locked, as you say.

Yeah, this solves the reported bug.

This is not a 100% solution: there's the cases when the user is removed
from an ACL and from a policy, and those deletions are done directly
instead of accumulating to the end for a mass deletion.

I had to export AcquireDeletionLock (previously a static in
dependency.c). I wonder if I should export ReleaseDeletionLock too, for

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachment Content-Type Size
lock-shdepDrop.patch text/x-diff 3.3 KB

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