Re: asynchronous execution

On Mon, Mar 13, 2017 at 1:06 AM, Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
wrote:

>
>> I think it will, because Append itself has been made async-capable by one
>> of the patches and UNION ALL uses Append. But as mentioned above, only
>> the postgres_fdw foreign tables will be able to utilize this for now.
>>
>>
> Ok, I'll re-run my test from a few weeks back and see if anything has
> changed.
>

I'm not able to discern any difference in plan between a 9.6 instance and
this patch.

The basic outline of my test is:

EXPLAIN ANALYZE
SELECT c1, c2, ..., cN FROM tab1 WHERE date = '1 day ago'
UNION ALL
SELECT c1, c2, ..., cN FROM tab2 WHERE date = '2 days ago'
UNION ALL
SELECT c1, c2, ..., cN FROM tab3 WHERE date = '3 days ago'
UNION ALL
SELECT c1, c2, ..., cN FROM tab4 WHERE date = '4 days ago'

I've tried this test where tab1 through tab4 all are the same postgres_fdw
foreign table.
I've tried this test where tab1 through tab4 all are different foreign
tables pointing to the same remote table sharing a the same server
definition.
I've tried this test where tab1 through tab4 all are different foreign
tables pointing each with it's own foreign server definition, all of which
happen to point to the same remote cluster.

Are there some postgresql.conf settings I should set to get a decent test?