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From: Tom Lane <[email protected]>
To: Daniel Verite <[email protected]>
Cc: [email protected]
Subject: Re: pgbench client-side performance issue on large scripts
Date: Mon, 24 Feb 2025 15:30:59 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

I wrote:
> Yeah, we do rely on yylineno in bootscanner.l and ecpg, but not
> elsewhere; not sure if there's a performance reason for that.

Ah: the flex manual specifically calls out "%option yylineno"
as something that has a moderate performance cost.  So that's
why we don't use it except in non-performance-critical scanners.

Now, it could be argued that pgbench's script scanner doesn't
rise to that level of performance-criticalness, especially not
if we're paying the cost of counting newlines some other way.
I'm not excited about doing a lot of performance analysis here
to decide that.  I think we could steal plpgsql's idea to
keep the code structure basically the same while avoiding the
O(N^2) repeat scans, and that should be enough.

			regards, tom lane

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