| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>, postgres performance list <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Strange choice of general index over partial index |
| Date: | 2015-01-16 03:28:34 |
| Message-ID: | 54B88562.4040500@agliodbs.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
On 01/16/2015 04:17 PM, Mark Kirkwood wrote:
> On 16/01/15 16:06, Mark Kirkwood wrote:
>
>> A bit more poking about shows that the major factor (which this fake
>> dataset anyway) is the default for effective_cache_size (changes from
>> 128MB to 4GB in 9.4). Increasing this makes 9.2 start using the
>> files_in_flight index in a plain index scan too.
>>
>
> Arrg - misread the planner output....in 9.2 what changes is a plan that
> uses an index scan on the *file_state* index (not
> files_in_flight)...which appears much faster than the bitmap scan on
> file_state. Apologies for the confusion.
>
> I'm thinking that I'm seeing the effect Tom has just mentioned.
It's not using a bitmapscan in either case; it's a straight indexscan.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Huan Ruan | 2015-01-16 03:32:03 | Re: shared_buffers vs Linux file cache |
| Previous Message | Mark Kirkwood | 2015-01-16 03:17:12 | Re: Strange choice of general index over partial index |