Yea seems right. I was testing the expression on Rubular (Which uses the
Ruby parser) and it worked. I guess Ruby allows this non-standard
expression with the missing lower bounds. Every reference I could find,
though, agrees only the upper bound is optional.
On Thu, Jul 24, 2014 at 1:42 PM, David G Johnston <
david.g.johns...@gmail.com> wrote:
> Mike Christensen-2 wrote
> > I'm curious why this query returns 0:
> >
> > SELECT 'AAA' ~ '^A{,4}$'
> >
> > Yet, this query returns 1:
> >
> > SELECT 'AAA' ~ '^A{0,4}$'
> >
> > Is this a bug with the regular expression engine?
>
> Apparently since "{,#}" is not a valid regexp expression the engine simply
> interprets it as a literal and says 'AAA' != 'A{,4}'
>
>
> http://www.postgresql.org/docs/9.3/interactive/functions-matching.html#FUNCTIONS-POSIX-REGEXP
>
> Table 9-13. Regular Expression Quantifiers
>
> Note the all of the { } expressions have a lower bound (whether explicit or
> implied).
>
> David J.
>
>
>
>
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