Re: [9.2] crash on regex

On 24 May 2012 16:24, Thom Brown <thom@linux.com> wrote:
> On 24 May 2012 16:08, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Thu, May 24, 2012 at 10:16 AM, Marko Kreen <markokr@gmail.com> wrote:
>>> Following query crashes backend on 9.2:
>>>
>>>  select substring('asd TO foo' from ' TO (([a-z0-9._]+|"([^"]+|"")+")+)');
>>
>> I spent some time trying to reduce this to the simplest case that
>> still causes a crash, and came up with this:
>>
>> select substring('a' from '((a))+');
>
> It appears to occur with any quantifier attached to a group that is
> more than 1 level deep with nothing between the groups, such as
> ((a))?, ((a))*, ((a)){1,4}, (((a)))+
>
> Or if the quantifier is the only additional thing between the groups,
> such as ((a)+)
>
> But when breaking the groups up, it's fine, so this works: ((a)b)+

Hmmm... curiously, lazy (non-greedy) quantifiers are stable, such as: ((a))*?

--
Thom