From: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
---|---|
To: | "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru>, Teodor Sigaev <teodor(at)sigaev(dot)ru> |
Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: POC: GROUP BY optimization |
Date: | 2022-03-15 08:26:47 |
Message-ID: | 9af89543-3d17-4c98-59de-1daa5bceeb06@enterprisedb.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 2/10/22 10:00, Andrey V. Lepikhov wrote:
> On 1/22/22 01:34, Tomas Vondra wrote:
>>
>
> I rebased (with minor fixes) this patch onto current master.
>
> Also, second patch dedicated to a problem of "varno 0" (fake_var).
> I think, this case should make the same estimations as in the case of
> varno != 0, but no any stats found. So I suppose to restrict number of
> groups with min of a number of incoming tuples and DEFAULT_NUM_DISTINCT
> value.
>
Thanks for the rebase. The two proposed changes (tweaked costing and
simplified fake_var handling) seem fine to me. I think the last thing
that needs to be done is cleanup of the debug GUCs, which I added to
allow easier experimentation with the patch.
I probably won't remove the GUCs entirely, though. I plan to add a
single GUC that would enable/disable this optimization. I'm not a huge
fan of adding more and more GUCs, but in this case it's probably the
right thing to do given the complexity of estimating cost with
correlated columns etc.
regards
--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
Attachment | Content-Type | Size |
---|---|---|
0001-Optimize-order-of-GROUP-BY-keys-20220315.patch | text/x-patch | 102.1 KB |
0002-Use-default-restriction-for-number-of-group-20220315.patch | text/x-patch | 2.1 KB |
0003-fixup-tweak-costing-20220315.patch | text/x-patch | 3.4 KB |
From | Date | Subject | |
---|---|---|---|
Next Message | Tomas Vondra | 2022-03-15 08:30:44 | Re: Column Filtering in Logical Replication |
Previous Message | Kyotaro Horiguchi | 2022-03-15 08:23:40 | Re: Add checkpoint and redo LSN to LogCheckpointEnd log message |