Re: patch adding new regexp functions

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: Jeremy Drake <pgsql(at)jdrake(dot)com>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Patches <pgsql-patches(at)postgresql(dot)org>, Neil Conway <neilc(at)samurai(dot)com>, David Fetter <david(at)fetter(dot)org>
Subject: Re: patch adding new regexp functions
Date: 2007-02-17 08:02:24
Message-ID: 200702170902.26138.peter_e@gmx.net
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Jeremy Drake wrote:
> In case you haven't noticed, I am rather averse to making this return
> text[] because it is much easier in my experience to use the results
> when returned in SETOF rather than text[],

The primary use case I know for string splitting is parsing
comma/pipe/whatever separated fields into a row structure, and the way
I see it your API proposal makes that exceptionally difficult.

I don't know what your use case is, though. All of this is missing
actual use cases.

> While, if you
> really really wanted a text[], you could use the (fully documented)
> ARRAY(select resultstr from regexp_split(...) order by startpos)
> construct.

I think, however, that we should be providing simple primitives that can
be combined into complex expressions rather than complex primitives
that have to be dissected apart to get simple results.

> > As for the regexp_matches() function, it seems to me that it
> > returns too much information at once. What is the use case for
> > getting all of prematch, fullmatch, matches, and postmatch in one
> > call?
>
> It was requested by David Fetter:
> http://archives.postgresql.org/pgsql-hackers/2007-02/msg00056.php
>
> It was not horribly difficult to provide, and it seemed reasonable to
> me. I have no need for them personally.

David Fetter has also repeated failed to offer a use case for this, so I
hesitate to accept this.

--
Peter Eisentraut
http://developer.postgresql.org/~petere/

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