Re: pgbench - add \aset to store results of a combined query

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pgbench - add \aset to store results of a combined query
Date: 2020-04-02 08:03:36
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On Thu, Apr 02, 2020 at 08:08:08AM +0200, Fabien COELHO wrote:
> ISTM that I submitted a patch to test whether a variable exists in pgbench,
> like available in psql (:{?var} I think), but AFAICS it did not pass. Maybe
> I should resurect it as it would allow to test simply whether an empty
> result was returned to aset, which could make sense in a bench script (get
> something, if it does not exist skip remainder… I can see some interesting
> use cases).

Not sure if improving the readability of the tests is a reason for
this patch. So I would suggest to just live with relying on debug()
for now to check that a variable with a given prefix exists.

> It does not need to create an UNLOGGED table, a mere "WHERE FALSE" suffices.

Good point, that's cheaper.

> I do not understand why you removed the comment about meta which makes it
> false, so I added something minimal back.

- * meta The type of meta-command, or META_NONE if command is SQL
+ * meta The type of meta-command. On SQL_COMMAND: META_NONE/GSET/ASET.

Oh, OK. I see your point. Sorry about that.

>> Perhaps we should also have a test where we return more than 1 row for
>> \get? The last point is unrelated to this thread though.
> Yes, but ISTM that it is not worth a dedicated patch… so I added a test
> similar to the one about empty aset.

Thanks. So, it looks like everything has been addressed. Do you have
anything else in mind?

NB: I think that it is really strange to not use an array for the
options in subroutine pgbench() of
Shouldn't this be an array of options instead? The current logic of
using a splitted string is weak when it comes to option quoting in
perl and command handling in general.

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