From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
---|---|
To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: update substring pattern matching syntax |
Date: | 2020-06-20 07:08:06 |
Message-ID: | alpine.DEB.2.22.394.2006200835570.859381@pseudo |
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Thread: | |
Lists: | pgsql-hackers |
Hello Peter,
> whereas the current standard says
>
> SUBSTRING(text SIMILAR pattern ESCAPE escapechar)
>
> The former was in SQL99, but the latter has been there since SQL:2003.
>
> It's pretty easy to implement the second form also, so here is a patch that
> does that.
Patches apply cleanly, compile and "make check" is ok. doc gen is ok as
well.
Grammar cleanup is a definite improvement as it makes the grammar closer
to the actual syntax.
I cannot say I'm a fan of this kind of keywords added for some arguments.
I guess that it allows distinguishing between variants. I do not have the
standard at hand: I wanted to check whether these keywords could be
reordered, i.e. whether SUBSTRING(text ESCAPE ec SIMILAR part) was legal.
I guess not.
Maybe the doc could advertise more systematically whether a features
conforms fully or partially to some SQL standards, or is pg specific. The
added documentation refers both to SQL:1999 and SQL99. I'd suggest to
chose one, possibly the former, and use it everywhere consistently.
It seems that two instances where not updated to the new syntax, see in
./src/backend/catalog/information_schema.sql and
./contrib/citext/sql/citext.sql.
--
Fabien.
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