From: Andres Freund <andres(at)anarazel(dot)de>
To: Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>,Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>,Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>,David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: ALTER TABLE ADD COLUMN fast default
Date: 2018-02-20 17:43:45
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On February 20, 2018 5:03:58 AM PST, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> wrote:
>On 20/02/18 07:42, Andres Freund wrote:
>> Hi,
>> On 2018-02-17 00:23:40 +0100, Tomas Vondra wrote:
>>> Anyway, I consider the performance to be OK. But perhaps Andres
>>> comment on this too, as he requested the benchmarks.
>> My performance concerns were less about CREATE TABLE related things
>> about analytics workloads or such, where deforming is the primary
>> bottleneck. I think it should be ok, but doing a before/after tpc-h
>> scale 5-10 or so wouldn't be a bad thing to verify.
>The test Tomas is doing is analytical query, it's running sum on the
>fast default column.
>He uses create and create-alter names as comparison between when the
>table was created with the columns and when the columns were added
>fast default.

It's still a fairly simplistic test case. Running some queries with reasonably well known characteristics seems like a good idea regardless. It's not like a scale 5 run takes that long.

Sent from my Android device with K-9 Mail. Please excuse my brevity.

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