Re: REGEXP_MATCHES() strange behavior with '^' and '$' pattern

Oops forgot patch.

Attached now.

On Wed, Jul 31, 2013 at 6:03 PM, Jeevan Chalke <
jeevan(dot)chalke(at)enterprisedb(dot)com> wrote:

> Hi,
>
> While playing with regular expression I found some strange behavior of
> regexp_matches() function.
>
> Consider following sql query and its output:
>
> postgres=# select regexp_matches('1' || chr(10) || '2' || chr(10) || '3'
> || chr(10) || '4', '^', 'mg');
> regexp_matches
> ----------------
> {""}
> {""}
> {""}
> {""}
> {""}
> {""}
> {""}
> (7 rows)
>
> It suppose to return me 4 rows and not 7. Similar behavior found with
> pattern '$'.
>
> It seems that these start and end anchor characters are not matching
> correctly. Or rather they are matching twice.
>
> To get a root cause of it, I put elog(INFO,..) into the
> setup_regexp_matches() function where we copy matches into the struct and
> found following values.
>
>
> postgres=# select regexp_matches('1' || chr(10) || '2' || chr(10) || '3'
> || chr(10) || '4', '^', 'mg');
> INFO: start_search: 0 rm_so: 0 rm_eo: 0
> INFO: updated start_search: 1
> INFO: start_search: 1 rm_so: 2 rm_eo: 2
> INFO: updated start_search: 2
> INFO: start_search: 2 rm_so: 2 rm_eo: 2
> INFO: updated start_search: 3
> INFO: start_search: 3 rm_so: 4 rm_eo: 4
> INFO: updated start_search: 4
> INFO: start_search: 4 rm_so: 4 rm_eo: 4
> INFO: updated start_search: 5
> INFO: start_search: 5 rm_so: 6 rm_eo: 6
> INFO: updated start_search: 6
> INFO: start_search: 6 rm_so: 6 rm_eo: 6
> INFO: updated start_search: 7
>
> Certainly, after second pass, updated start_search should be 3 as last
> matched pattern was at 2 and of zero length since so = eo.
>
> I have modified that logic to look similar as that of replace_text_regexp()
> function. As regexp_replace works well.
>
> Attached patch with test-case. Please have a look and let me know if I
> assumed something wrong.
>
> Thanks
>
> --
> Jeevan B Chalke
>
>

--
Jeevan B Chalke