Re: The TODO List (Was: Re: Open 7.3 items)

Re-added to open items:

Fix SIMILAR TO to be ANSI compliant or remove it (Peter, Tom)

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Tom Lane wrote:
> "Marc G. Fournier" <scrappy(at)hub(dot)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
>
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