From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Thomas Munro <thomas.munro@gmail.com>, Kirk Wolak <wolakk@gmail.com>,
        pgsql-general@lists.postgresql.org
Subject: Re: Getting PSQL in Windows to support TAB/Autocomplete via modified
 readline...
In-reply-to: <20221124004144.iosgze2qnmcctgsh@awork3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Wed, 23 Nov 2022 16:41:44 -0800"
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Date: Wed, 23 Nov 2022 20:28:29 -0500
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Andres Freund <andres@anarazel.de> writes:
> On 2022-11-23 18:11:22 -0500, Tom Lane wrote:
>> Huh ... do you recall the details?  Large as tab-complete is, it's
>> far smaller than gram.y:

> So It might just be that we need to split up that very long "else if" ch=
ain in
> psql_completion().

Could be, yeah.  Related point: I've wondered for awhile how long that
chain can get before we start noticing performance issues on slower
machines.  Even when the standard is just human reaction time, there's
a limit to how many cycles you can throw away.  So I'd like to see it
refactored somehow to be a bit less stupid --- but I have a nagging
feeling that we'd end up building some special-purpose program generator,
which is something I've not wanted to do.  OTOH, in the best of all
possible worlds such a tool might make it easier to add tab
completions?

(In the past I've fantasized about auto-generating tab completion
logic from the backend grammar, but I fear it's just fantasy.
The backend grammar isn't factored right, and too many of its names
don't have clear traceability to what-kind-of-object-is-that.)

			regards, tom lane