Re: problems with foreign keys on partitioned tables

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: problems with foreign keys on partitioned tables
Date: 2019-01-24 17:18:11
Message-ID: 201901241718.yvif6bp7oaed@alvherre.pgsql
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On 2019-Jan-24, Amit Langote wrote:

> A few hunks of the originally proposed patch are attached here as 0001,
> especially the part which fixes ATAddForeignKeyConstraint to pass the
> correct value of connoninherit to CreateConstraintEntry (which should be
> false for partitioned tables). With that change, many tests start failing
> because of the above bug. That patch also adds a test case like the one
> above, but it fails along with others due to the bug. Patch 0002 is the
> aforementioned simpler fix to make the errors (existing and the newly
> added) go away.

Cool, thanks. I made a bunch of fixes -- I added an elog(ERROR) check
to ensure a constraint whose parent is being set does not already have a
parent; that seemed in line with the new asserts that check the
coninhcount. I also moved those asserts, changing the spirit of what
they checked. Also: I wasn't sure about stopping recursion for legacy
inheritance in ATExecDropConstraint() for non-check constraints, so I
changed that to occur in partitioned only. Also, stylistic fixes.

I was mildly surprised to realize that the my_fkey constraint on
fk_part_1_1 is gone after dropping fkey on its parent, since it was
declared locally when that table was created. However, it makes perfect
sense in retrospect, since we made it dependent on its parent. I'm not
terribly happy about this, but I don't quite see a way to make it better
that doesn't require much more code than is warranted.

> These patches apply unchanged to the PG 11 branch.

Yeah, only if you tried to compile, it would have complained about
table_close() ;-)

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

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