Re: ALTER TABLE ADD COLUMN fast default

On February 20, 2018 5:03:58 AM PST, Petr Jelinek <petr.jelinek@2ndquadrant.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
>could
>>> comment on this too, as he requested the benchmarks.
>>
>> My performance concerns were less about CREATE TABLE related things
>than
>> about analytics workloads or such, where deforming is the primary
>> bottleneck.  I think it should be ok, but doing a before/after tpc-h
>of
>> 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
>new
>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
>using
>fast default.

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

Andres
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