Feedback-ID: id4a34324:Fastmail
Date: Wed, 23 Aug 2023 15:06:12 -0700
From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Daniel Gustafsson <daniel@yesql.se>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
	Thomas Munro <thomas.munro@gmail.com>,
	Justin Pryzby <pryzby@telsasoft.com>,
	Nazir Bilal Yavuz <byavuz81@gmail.com>
Subject: Re: Cirrus-ci is lowering free CI cycles - what to do with cfbot,
 etc?
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Hi,

On 2023-08-23 17:55:53 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On 2023-08-23 17:02:51 -0400, Tom Lane wrote:
> >> ... unless we hit problems with, say, a different default port number or
> >> socket path compiled into one copy vs. the other?  That seems like it's
> >> probably a "so don't do that" case, though.
>
> > If we were to find such a case, it seems we could just add whatever missing
> > parameter to the connection string? I think we would likely already hit such
> > problems though, the psql started by an installcheck pg_regress might use the
> > system libpq, I think?
>
> The trouble with that approach is that in "make installcheck", we
> don't really want to assume we know what the installed libpq's default
> connection parameters are.  So we don't explicitly know where that
> libpq will connect.

Stepping back: I don't think installcheck matters for the concrete use of
libpq we're discussing - the only time we wait for server startup is the
non-installcheck case.

There are other potential uses for libpq in pg_regress though - I'd e.g. like
to have a "monitoring" session open, which we could use to detect that the
server crashed (by waiting for the FD to be become invalid). Where the
connection default issue could matter more?

I was wondering if we could create an unambiguous connection info, but that
seems like it'd be hard to do, without creating cross version hazards.


> As I said, we might be able to start treating installed-libpq-not-
> compatible-with-build as a "don't do it" case.  Another idea is to try
> to ensure that pg_regress uses the same libpq that the psql-under-test
> does; but I'm not sure how to implement that.

I don't think that's likely to work, psql could use a libpq with a different
soversion. We could dlopen() libpq, etc, but that seems way too complicated.


What's the reason we don't force psql to come from the same build as
pg_regress?

Greetings,

Andres Freund