From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Dunstan <andrew@dunslane.net>
cc: pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Declare assorted array functions using anycompatible not
 anyelem
In-reply-to: <b300679b-6410-9124-271c-73893a2c3a1f@dunslane.net>
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Comments: In-reply-to Andrew Dunstan <andrew@dunslane.net>
	message dated "Mon, 09 Nov 2020 17:00:05 -0500"
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Date: Mon, 09 Nov 2020 17:15:49 -0500
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Andrew Dunstan <andrew@dunslane.net> writes:
> On 11/9/20 4:29 PM, Tom Lane wrote:
>> I think probably the right fix is just to change that test case to
>> use a different implementation function, per [1].  I'm holding off
>> pushing the fix till after this week's wraps, though.

> I'd be ok with that. Can we devise a fix that will work all the way back
> to 9.2, which is where we start upgrade testing?

Hm.  To fix it this way, we'd have to push the test-script change
into the pre-9.5 branches.  There's no technical reason we can't do
that, I don't think, though it's a bit outside our normal practices.

>> If I thought that user-defined aggregates relying on array_cat were
>> really a thing (and not just a test case), I'd be more concerned about
>> this.  But it's hard to see why users shouldn't use array_agg() instead
>> of rolling their own.

> Possibly something that's been migrated from before we had array_agg.

array_agg goes back to 8.4, and for at least most of that time it's
been very much more efficient than anything based on array_cat.  So I
think it's past time to push any such laggards into the 21st century.

			regards, tom lane