From: Tom Lane <tgl@sss.pgh.pa.us>
To: Amit Langote <amitlangote09@gmail.com>
cc: Pavel Stehule <pavel.stehule@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: plan cache overhead on plpgsql expression
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Comments: In-reply-to Amit Langote <amitlangote09@gmail.com>
	message dated "Thu, 26 Mar 2020 19:56:32 +0900"
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Date: Thu, 26 Mar 2020 13:39:52 -0400
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Amit Langote <amitlangote09@gmail.com> writes:
> One thing -- I don't get the division between
> CachedPlanAllowsSimpleValidityCheck() and CachedPlanIsSimplyValid().
> Maybe I am missing something, but could there not be just one
> function, possibly using whether expr_simple_expr is set or not to
> skip or do, resp., the checks that the former does?

Well, we don't want to do the initial checks over again every time;
we want the is-valid test to be as simple and fast as we can make it.
I suppose we could have one function with a boolean flag saying "this is a
recheck", but I don't find that idea to be any better than the way it is.

Also, although the existing structure in plpgsql always calls
CachedPlanIsSimplyValid immediately after a successful call to
CachedPlanAllowsSimpleValidityCheck, I don't think that's necessarily
going to be true for other potential users of the functions.
So merging the functions would reduce flexibility.

			regards, tom lane