Horton

Re: [BUG] Fix DETACH with FK pointing to a partitioned table fails

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Tender Wang <tndrwang@gmail.com>
Cc: Alexander Lakhin <exclusion@gmail.com>, Jehan-Guillaume de Rorthais <jgdr@dalibo.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Guillaume Lelarge <guillaume@lelarge.info>
Date: 2024-10-28T09:16:17Z
Lists: pgsql-hackers

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On 2024-Oct-27, Tender Wang wrote:

> BTW, while reviewing the v2 patch, I found the parentConTup in
> foreach(cell, fks) block
> didn't need it anymore. We can remove the related codes.

True.  Done so in this v3.

I noticed another problem here: we're grabbing the wrong lock type on
the referenced rel (AccessShareLock) during detach.  (What's more: we
release it afterwards, which is the wrong thing to do.  We need to keep
such locks until end of transaction).  I didn't try to construct a case
where this would be a problem, but if I change AccessShare to NoLock,
the assertion that says we don't hold _any_ lock on that relation fires,
which means that we're not taking any locks on those rels before this
point.  So this lock strength choice is definitely wrong.  I changed it
to ShareRowExclusive, which is what we're suppose to use when adding a
trigger.  Another option might be to do find_all_inheritors() ahead of
time to grab all the necessary locks, but I didn't try to do that.  I
also added an assertion in addFkRecurseReferenced to verify that we hold
that in all paths, and after this change it doesn't fire anymore with
the regression tests.

I have still not edited the commit message.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/

Commits

  1. Fix some more bugs in foreign keys connecting partitioned tables

  2. Restructure foreign key handling code for ATTACH/DETACH

  3. Create foreign key triggers in partitioned tables too