From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas@vondra.me>
cc: pgsql-hackers@lists.postgresql.org
Subject: Re: libedit history seems to be misbehaving / broken
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Comments: In-reply-to Tomas Vondra <tomas@vondra.me>
	message dated "Sun, 27 Oct 2024 18:47:10 +0100"
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Date: Sun, 27 Oct 2024 15:03:06 -0400
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Tomas Vondra <tomas@vondra.me> writes:
> I'm not terribly familiar with libedit, so can't say if it's a bug in
> libedit, or if we're just using it wrong in some way. I investigated
> that while on a flight from pgconf.eu, but can't look into this further.
> So let me at least share the behavior I observed, and what I found.
> Note: All of this is with libedit-3.1-53.20240808cvs.fc40.x86_64, which
> is what I currently get in Fedora 40.

libedit has been a hot mess for a long time.  psql's input.c has
workarounds for assorted bugs that it has or had in prior versions,
and what I suspect is that latest libedit has a different set of bugs.

FWIW, I don't observe any particular misbehavior with the very ancient
libedit that macOS ships.  On Fedora 39, I notice something related to
what you say: it seems like the "\q" ending a session gets repeated
into .psql_history by the next session.  I'm surprised that it's not
exactly the same as your results though, because it seems to be the
same source version:

$ rpm -q libedit
libedit-3.1-53.20240808cvs.fc39.x86_64

Didn't try the too-many-lines behavior, but it looks like that
is implemented totally by history_truncate_file(), so if that's
busted it's surely their fault.

			regards, tom lane