On Tue, 19 Feb 2002, Peter R. Wood (Lists) wrote:
> >
> > If so, your \s+ fails. I don't use Oracle, so I can't check any of this,
> > but what about this?
> >
> > /*+ FIRST_ROWS */ /*+ DOMAIN_INDEX_SORT */
> >
> > If so, your .* should be .*?
> >
>
> .* = match a single character zero or more times, yes?
> .*? = the above condition, but only zero or one instances of the above?
> What would the .*? do for me?
In your example, "zero or more characters" could match either "FIRST_ROWS"
or "FIRST_ROWS */ /*+ DOMAIN_INDEX_SORT" while allowing the full pattern
to match. .* will match the latter, .*? will match the former.
>From the perlre manpage:
By default, a quantified subpattern is "greedy", that is, it will
match as many times as possible (given a particular starting loca
tion) while still allowing the rest of the pattern to match. If
you want it to match the minimum number of times possible, follow
the quantifier with a "?". Note that the meanings don't change,
just the "greediness":
*? Match 0 or more times
+? Match 1 or more times
?? Match 0 or 1 time
Excessively greedy quantifiers are a very common error. :)
Alan
