Date: Wed, 24 Jan 2018 12:43:59 -0800
From: Andres Freund <andres@anarazel.de>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>,
	Thomas Munro <thomas.munro@enterprisedb.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: pgsql: Add parallel-aware hash joins.
Message-ID: <20180124204359.ognamsfdqbrfbazd@alap3.anarazel.de>
References: <20180124182018.jx2h4wp6twqo7xix@alap3.anarazel.de>
 <20180124201826.g6vhuewpnycpt3ta@alvherre.pgsql>
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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