| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Should total_pages be calculated after partition pruning and constraint exclusion? |
| Date: | 2018-05-15 19:46:01 |
| Message-ID: | CAKJS1f_eUz0_h5_vU1rqE7wuxMcoENcWK2FTODz0pOyxp3_Uig@mail.gmail.com |
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| Lists: | pgsql-hackers |
It seems quite strange to me that we calculate total_pages before any
partition pruning and constraint exclusion is performed during
set_base_rel_sizes(). Wouldn't it be better to wait until after that's
done so we don't mistakenly count relations we're not going to scan?
Delaying the calculation until after set_base_rel_sizes() means it's
still done in time before it's needed in set_base_rel_pathlists().
The attached patch implements the change.
There are no visible plan changes in the regression tests, but the
change can affect the plans for larger partitioned tables.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| Attachment | Content-Type | Size |
|---|---|---|
| total_pages_after_pruning.patch | application/octet-stream | 3.7 KB |
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