| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: open/lseek overhead with many partitions (including with "faster partitioning pruning") |
| Date: | 2018-04-04 00:27:25 |
| Message-ID: | CAKJS1f8DjC+iWH4CCeChN0=cS8=U+t9JBnVoH6sz=dVhnUbRYw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 4 April 2018 at 07:46, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> TLDR: even with "faster pruning" patch, pg11dev open()+lseek() every file
> backing every table being queried, even for those partitions eventually
> "excluded".
Yeah, this will no doubt be due to the fact that we still build
RelOptInfos in the planner for all partitions, so we're still doing
get_relation_info() and estimate_rel_size() for each of those. It
might be possible to delay that call until we know we're going to need
the partition. I imagine we wouldn't need to know the size of the
relation until after set_rel_sizes, but I've not checked.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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