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

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [COMMITTERS] pgsql: Add notion of a "transform function" that can simplify function
Date: 2012-03-23 15:25:58
Message-ID: CA+Tgmob_qbwXxVsVRYuKAHQWDgOFon+qV-QUAnrHD83COtqcEg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
On Fri, Mar 23, 2012 at 10:55 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> 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.

I assumed that we were merely trying to avoid forcing the caller to
provide the expression tree if they didn't have it handy, and that the
comment was merely making allowance for the fact that someone might
want to do such a thing.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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