Subject: Re: [Suspect SPAM] Re: pgsql: Add pg_partition_root to display
 top-most parent of a partition
References: <E1grthW-00078n-Az@gemulon.postgresql.org>
 <20190322032612.GA323@alvherre.pgsql> <20190322035538.GO20192@paquier.xyz>
From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Message-ID: <06be11a6-fd8d-b68b-1b97-1bafb1d3185c@lab.ntt.co.jp>
Date: Fri, 22 Mar 2019 13:09:23 +0900
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To: Michael Paquier <michael@paquier.xyz>,
        Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: pgsql-committers@lists.postgresql.org
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Hi,

On 2019/03/22 12:55, Michael Paquier wrote:
> On Fri, Mar 22, 2019 at 12:26:12AM -0300, Alvaro Herrera wrote:
>> I noticed days ago that if you call pg_partition_root on the topmost
>> partitioned table, the server crashes :-)

I thought we already fixed that last month, but that was pg_partition_tree().

> It's when you think that the thing is actually done that another issue
> pops up.  The attached fixes the issue, I suggest to return the
> top-most parent as result if the input is the top-most parent itself.
> Returning NULL does not make sense as in this case the relation can be
> part of a partition tree.

Thanks for writing the patch.

 	/* Fetch the top-most parent */
 	ancestors = get_partition_ancestors(relid);

Maybe, the patch should update this comment to say "Fetch the list of
ancestors".

+
+	/*
+	 * If the listed partition is already the top-most parent, just
+	 * return itself.
+	 */

What does "listed partition" mean?  Maybe, you mean "If the input
relation..."?  How about write this as:

If the input relation is itself the top-most parent, just return itself.

Regards,
Amit