Re: pgsql: Add parallel-aware hash joins. - Mailing list pgsql-hackers

From Andres Freund
Subject Re: pgsql: Add parallel-aware hash joins.
Date
Msg-id 20180124204359.ognamsfdqbrfbazd@alap3.anarazel.de
Whole thread Raw
In response to Re: pgsql: Add parallel-aware hash joins.  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Responses Re: pgsql: Add parallel-aware hash joins.
List pgsql-hackers
Hi,

On 2018-01-24 17:18:26 -0300, Alvaro Herrera wrote:
> Andres Freund wrote:
> > Besides larger groups, starting the next test(s) earlier, another way to
> > gain pretty large improvements would be a test schedule feature that
> > allowed to stat dependencies between tests. So instead of manually
> > grouping the schedule, have 'numerology' state that it depends on int2,
> > int4, int8, float4, float8, which means it can actually be started
> > earlier than it currently can in many cases.
> 
> Yeah, I proposed this a decade ago but never had the wits to write the
> code.

It shouldn't be too hard, right? Leaving defining the file format,
parsing it, creating the new schedule with depencencies and adapting
tests aside (hah), it mostly seems a relatively simple graph ordering /
topological sort problem, right?  If we keep the timings from an earlier
run somwhere, we can use the timing of runs as edge weights, making the
schedule better.


> It would be very useful for running tests standalone, too -- much as I
> dislike 'make installcheck' taking half a minute, I dislike much more
> having to take 5 minutes each time to figure out that create_table
> depends on box, polygon, create_function, yadda yadda.

Oh, that's a good point.

- Andres


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