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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: Jonathan S. Katz <jkatz@postgresql.org>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Steven Pousty <steve.pousty@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Isaac Morland <isaac.morland@gmail.com>
Cc: Pierre Giraud <pierre.giraud@dalibo.com>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Poll: are people okay with function/operator table redesign?
Date: Tue, 05 May 2020 10:07:03 -0400
Message-ID: <19999.1588687623@sss.pgh.pa.us> (raw)
In-Reply-To: <CAEZATCWd+KVKvZzt-7sQy6gDXNQe64qEcDKMjNadSEhaLpqwow@mail.gmail.com>
References: <20200423174343.GA16996@alvherre.pgsql>
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	<b1f89d14-cd7f-e43d-964e-9fb04e209b72@postgresql.org>
	<751.1588627321@sss.pgh.pa.us>
	<CAEZATCWd+KVKvZzt-7sQy6gDXNQe64qEcDKMjNadSEhaLpqwow@mail.gmail.com>

Dean Rasheed <dean.a.rasheed@gmail.com> writes:
> On Mon, 4 May 2020 at 22:22, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Now I could have done this example by spelling out all six varieties of
>> stddev() separately, and maybe I should've, but it seemed overly bulky
>> that way.

> FWIW, I prefer having each variety spelled out separately. For
> example, I really like the new way that aggregates like sum() and
> avg() are displayed. To me, having all the types listed like that is
> much more readable than having to read and interpret a piece of free
> text.

> Similarly, for other functions like gcd(), lcm() and mod(). I think it
> would be better to get rid of numeric_type, and just list all the
> variants of each function.

I had had the same idea to start with, but it didn't survive first contact
with table 9.4 (Mathematical Operators).  It's not really reasonable to
spell out all the variants of + ... especially not if you want to be
precise, because then you'd have to list the cross-type variants too.
If I counted correctly, there are fourteen variants of binary + that
would have to be listed in that table, never mind the other common
operators.

max() and min() have a similar sort of problem --- the list of variants
is just dauntingly long, and it's not that interesting either.
I wrote out sum() and avg() the way I did because they have a somewhat
irregular mapping from input to output types, so it seemed better to
just list the alternatives explicitly.

I don't object too much to spelling out the variants of stddev()
and variance(), if there's a consensus for that.  But getting rid
of "numeric_type" entirely seems impractical.

			regards, tom lane





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  Cc: tgl@sss.pgh.pa.us, dean.a.rasheed@gmail.com, jkatz@postgresql.org, peter.eisentraut@2ndquadrant.com, bruce@momjian.us, alvherre@2ndquadrant.com, robertmhaas@gmail.com, steve.pousty@gmail.com, pavel.stehule@gmail.com, isaac.morland@gmail.com, pierre.giraud@dalibo.com, pgsql-hackers@lists.postgresql.org
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