Re: FW: Constraint exclusion in partitions

On Fri, May 22, 2015 at 10:21 AM, Daniel Begin <jfd553(at)hotmail(dot)com> wrote:

> But how constraint exclusion would react with the following queries …
>
> b- Select * from parent_table where id between 2345 and 6789; --
> using a range of ids
>
​Not sure...
​

These are constants but I'm not sure how smart the planner is about
figuring out inequalities of this form.

I would guess yes but it should be easy enough to confirm this yourself
using explain...you already have the tables.

> c- Select * from parent_table where id in(select ids from
> anothertable); -- using a list of ids from a select
>
Definitely no...

Constraint exclusion is done by the planner before data is read so there is
no possible way for data in a table to be used.​

As for performance the only way to know for sure is to test your usage
patterns and data. Even without constraint exclusion partitioning can
provide benefits.

David J.