Feedback-ID: ia2694551:Fastmail
Date: Mon, 27 Nov 2023 15:06:12 +0100
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Andrew Dunstan <andrew@dunslane.net>
Cc: Amit Langote <amitlangote09@gmail.com>, 
	Andres Freund <andres@anarazel.de>, jian he <jian.universality@gmail.com>, 
	Erik Rijkers <er@xs4all.nl>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: remaining sql/json patches
Message-ID: <202311271406.budphctjy3p3@alvherre.pgsql>
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On 2023-Nov-27, Andrew Dunstan wrote:

> Interesting. But inferring a speed effect from such changes is difficult. I
> don't have a good idea about measuring parser speed, but a tool to do that
> would be useful. Amit has made a start on such measurements, but it's only a
> start. I'd prefer to have evidence rather than speculation.

At this point one thing that IMO we cannot afford to do, is stop feature
progress work on the name of parser speed.  I mean, parser speed is
important, and we need to be mindful that what we add is reasonable.
But at some point we'll probably have to fix that by parsing
differently (a top-down parser, perhaps?  Split the parser in smaller
pieces that each deal with subsets of the whole thing?)

Peter told me earlier today that he noticed that the parser changes he
proposed made the parser source code smaller, they result in larger
parser tables (in terms of the number of states, I think he said).  But
source code maintainability is also very important, so my suggestion
would be that those changes be absorbed into Amit's commits nonetheless.

The amount of effort spent on the parsing aspect on this thread seems in
line with what we should always be doing: keep an eye on it, but not
disregard the work just because the parser tables have grown.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"La persona que no quería pecar / estaba obligada a sentarse
 en duras y empinadas sillas    / desprovistas, por cierto
 de blandos atenuantes"                          (Patricio Vogel)