From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dmitry Dolgov <9erthalion6@gmail.com>
cc: Jeff Janes <jeff.janes@gmail.com>,
        Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>,
        Pavel Stehule <pavel.stehule@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: why partition pruning doesn't work?
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Comments: In-reply-to Dmitry Dolgov <9erthalion6@gmail.com>
	message dated "Sun, 03 Jun 2018 18:44:33 +0200"
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Date: Sun, 03 Jun 2018 13:11:40 -0400
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Dmitry Dolgov <9erthalion6@gmail.com> writes:
> Just to clarify for myself, for evaluating any stable function here woul=
d it be
> enough to handle all function-like expressions (FuncExpr / OpExpr /
> DistinctExpr / NullIfExpr) and check a corresponding function for provol=
atile,
> like in the attached patch?

I think the entire approach is wrong here.  Rather than concerning
yourself with Params, or any other specific expression type, you
should be using !contain_volatile_functions() to decide whether
an expression is run-time-constant.  If it is, use the regular
expression evaluation machinery to extract the value.

			regards, tom lane