Re: regex help wanted

On Thu, Apr 25, 2013 at 03:40:51PM +0100, Thom Brown wrote:

> On 25 April 2013 15:32, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Karsten Hilbert <Karsten(dot)Hilbert(at)gmx(dot)net> writes:
> >> What I don't understand is: Why does the following return a
> >> substring ?
> >
> >> select substring ('junk $<allergy::test::99>$ junk' from '\$<[^<]+?::[^:]+?>\$');
> >
> > There's a perfectly valid match in which [^<]+? matches allergy::test
> > and [^:]+? matches 99.
>
> Yeah, I think there may be an assumption that a lazy quantifier will
> stop short and cause the remainder to fail to match permanently, but
> it will backtrack, forcing the lazy quantifier to expand until it can
> match the expression.

Yup, therein lies the rub :-)

Thanks,
Karsten
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