Re: [HACKERS] pgbench - allow to store select results into variables

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Stephen Frost <sfrost(at)snowman(dot)net>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] pgbench - allow to store select results into variables
Date: 2019-01-10 09:12:26
Message-ID: alpine.DEB.2.21.1901100923110.13058@lancre
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Hello Alvaro,

> Here are my proposed final changes.

Thanks again for improving the patch!

> I noticed that you were allocating the prefixes for all cases even when
> there were no cset/gset in the command; I changed it to delay the
> allocation until needed.

Ok, why not.

> I also noticed you were skipping the Meta enum dance for no good reason;

Indeed. I think that the initial version of the patch was before the
"dance" was added, and it did not keep up with it.

> added that makes conditionals simpler. The read_response routine seemed
> misplaced and I gave it a name in a style closer to the rest of the
> pgbench code.


> Also, you were missing to free the ->lines pqexpbuffer when the command
> is discarded. I grant that the free_command() stuff might be bogus
> since it's only tested with a command that's barely initialized, but it
> seems better to make it bogus in this way (fixable if we ever extend its
> use) than to forever leak memory silently.


However, I switched "pg_free" to "termPQExpBuffer", which seems more
appropriate, even if it just does the same thing. I also ensured that
prefixes are allocated & freed. I've commented about expr which is not

> I didn't test this beyond running "make check".

That's a good start.

I'm not keen on having the command array size checked and updated *after*
the command is appended, even if the initial allocation ensures that there
is no overflow, but I let it as is.

Further tests did not yield any new issue.

Attached a v29 with the above minor changes wrt your version.


Attachment Content-Type Size
pgbench-into-29.patch text/x-diff 34.8 KB

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