| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | cost_agg() with AGG_HASHED does not account for startup costs |
| Date: | 2015-08-04 04:55:00 |
| Message-ID: | CAKJS1f9ygX3uFd4oHx_ZwrLTnEL1T8dqseHF2F4w9haCkhqJdQ@mail.gmail.com |
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During working on allowing the planner to perform GROUP BY before joining
I've noticed that cost_agg() completely ignores input_startup_cost
when aggstrategy == AGG_HASHED.
I can see at least 3 call to cost_agg() which pass aggstrategy as
AGG_HASHED that are also passing a possible non-zero startup cost.
The attached changes cost_agg() to include the startup cost, but does
nothing for the changed plans in the regression tests.
Is this really intended?
Regards
David Rowley
--
David Rowley http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Training & Services
| Attachment | Content-Type | Size |
|---|---|---|
| cost_agg_startup_cost.diff | text/plain | 604 bytes |
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