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