Date: Wed, 24 Jan 2018 12:47:33 -0800
From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Robert Haas <robertmhaas@gmail.com>,
	Thomas Munro <thomas.munro@enterprisedb.com>,
	"pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: pgsql: Add parallel-aware hash joins.
Message-ID: <20180124204733.i3mp5xpfyermlhgz@alap3.anarazel.de>
References: <20180124201826.g6vhuewpnycpt3ta@alvherre.pgsql>
 <18096.1516826195@sss.pgh.pa.us>
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Hi,

On 2018-01-24 15:36:35 -0500, Tom Lane wrote:
> There'd be a lot of followup work to sanitize the tests better.  For
> instance, if two tests transiently create tables named "foo", it doesn't
> matter as long as they're not in the same group.  It would matter with
> this.

Right. I suspect we'd initially end up with a schedule that'd had
dependencies pretty similar to what we have now as groups. I suspect
that even with a very small number of changes we'd get a lot better
timings.


> There are things we could do to mitigate that --- one attractive idea
> is to have each test create its own schema for transient objects.
> The limiting factor is that we don't want the test scripts to change
> so much that back-patching tests becomes impossible.  (Or at least,
> I'd not like that.)

I think a lot of temporary, potentially conflicting, objects are already
created as TEMPORARY. Adding a few more temporary markers shouldn't be
too hard.

> I'm concerned that we'd end up with a higher number of irreproducible
> test failures with no good way to investigate them.

Hm. We probably should dump the used ordering of tests somwhere upon
failure, to make it easier to debug.

Greetings,

Andres Freund