Re: The TODO List (Was: Re: Open 7.3 items) - Mailing list pgsql-hackers

On Wed, 18 Sep 2002, Bruce Momjian wrote:

>
> Re-added to open items:
>
>     Fix SIMILAR TO to be ANSI compliant or remove it (Peter, Tom)

Tke that @#$@$@@$@#$ thing out of there until its actually been fully
discussed ... you are starting to remind me of Charlie Brown ... this, I
think, was Thomas' whole point, in that things are added way too faster
and easily without fully understanding all of the ramifications ... let a
discussion cool down *before* you take things off, or add things to, the
list ...




>
> ---------------------------------------------------------------------------
>
> Tom Lane wrote:
> > "Marc G. Fournier" <scrappy@hub.org> writes:
> > > I'm in agreement with Thomas here ... unless a problem has been defined a
> > > bit more specifically then 'it isn't posix compliant', it shouldn't be
> > > considered an open item ... please remove?
> >
> > A quick review of SQL99 says that their notion of SIMILAR TO patterns
> > is an unholy witches' brew: it does *both* common-or-garden regexp
> > expressions and LIKE patterns.  Specifically, I see these
> > metacharacters:
> >
> >     |        OR  (regexp-ish)
> >
> >     *        repeat 0 or more times  (regexp-ish)
> >
> >     +        repeat 1 or more times  (regexp-ish)
> >
> >     %        match any character sequence  (like LIKE)
> >
> >     _        match any one character  (like LIKE)
> >
> >     [...]        almost-but-not-quite-regexp-ish character class
> >
> >     (...)        grouping  (regexp-ish)
> >
> > plus a just-like-LIKE treatment of a selectable escape character.
> >
> > But the most important variation from common regex practice is that
> > (if I'm reading the spec correctly) the pattern must match to the
> > entire target string --- ie, it's effectively both left- and right-
> > anchored.  This is like LIKE patterns but utterly unlike common regexp
> > usage.
> >
> > I could live with the fact that our regexp patterns don't implement all
> > of the spec-mandated metacharacters.  But I do not think we can ignore
> > the difference in anchoring behavior.  This is not a subset of the spec
> > behavior, it is just plain wrong.
> >
> > I vote with Peter: we fix this or we disable it before 7.3 release.
> > It is not anywhere near spec compliant, and we will be doing no one
> > a favor by releasing it in the current state.
> >
> >             regards, tom lane
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 4: Don't 'kill -9' the postmaster
> >
>
> --
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
>