Date: Thu, 6 Feb 2020 18:12:38 -0300
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: FK violation in partitioned table after truncating a referenced
 partition
Message-ID: <20200206211238.GA29108@alvherre.pgsql>
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On 2020-Feb-04, Jehan-Guillaume de Rorthais wrote:


> Please, find in attachment a bug fix proposal where a truncate on a
> partition cascade to the referencing table and truncate all its
> partitions if applicable.
> 
> The patch make sure heap_truncate_find_FKs find all referencing relations,
> directly **and indirectly** through their parent table.
> 
> When considering the various way of fixing this, I thought about calling
> find_all_inheritors on all relations returned by heap_truncate_find_FKs to add
> them to the list or relation to truncate (I have a working patch for this as
> well). However, I felt like heap_truncate_find_FKs was the real suspect here
> and was responsible to find all referencing relations.

Hello, thanks for reporting and patching.

I agree that patching heap_truncate_find_FKs is a reasonable way to fix.
I propose a slightly different formulation: instead of the loop that you
have, we can just use the second loop, and add more parent constraints
to the list if any constraint we scan in turn has a parent constraint.
So we don't repeat the whole thing, but only that second loop.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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