| From: | "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: POC: GROUP BY optimization |
| Date: | 2021-12-28 08:47:35 |
| Message-ID: | [email protected] |
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| Thread: | |
| Lists: | pgsql-hackers |
On 9/2/20 9:12 PM, Tomas Vondra wrote:
> We could simply use the input "tuples" value here, and then divide the
> current and previous estimate to calculate the number of new groups.
Performing a review of this patch I made a number of changes (see
cleanup.txt). Maybe it will be useful.
As I see, the code, which implements the main idea, is quite stable.
Doubts localized in the cost estimation routine. Maybe try to finish
this work by implementing an conservative strategy to a cost estimation
of sorting?
--
regards,
Andrey Lepikhov
Postgres Professional
| Attachment | Content-Type | Size |
|---|---|---|
| cleanup.txt | text/plain | 5.5 KB |
| group-by-reorder-20211228.patch | text/x-patch | 98.9 KB |
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