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