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Re: [COMMITTERS] pgsql: Add notion of a "transform function" that can simplify function

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: [COMMITTERS] pgsql: Add notion of a "transform function" that can simplify function
Date: 2012-03-23 14:55:52
Message-ID: 12822.1332514552@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
Robert Haas <rhaas(at)postgresql(dot)org> writes:
> Add notion of a "transform function" that can simplify function calls.

Why exactly was this thought to be a good idea:

> * A NULL original expression disables use of transform functions while
> * retaining all other behaviors.

AFAICT that buys nothing except to greatly complicate the API
specification for simplify_function, something that is now proving
problematic for Marti's requested refactoring [1].  If it's
inappropriate for a transform function to modify a CoerceViaIO call,
surely the transform function can be expected to know that.

			regards, tom lane

[1] http://archives.postgresql.org/pgsql-hackers/2012-03/msg00694.php

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