Re: POSIX RE starting with a (

On Wed, 2004-08-11 at 14:39, Nick Barr wrote:
> Hi,
>
> Just noticed something funny with the POSIX Regular expressions and
> wondered if it is a bug, or whether I am doing something wrong. I am
> using the POSIX RE in a function that is used in several places so would
> have to put some nasty if statement in there for this side case if there
> is not work around.
>
> ======================================================================
> intranet=# select track_id, track_name from ms_track where track_name
> like '(%';
>   track_id |           track_name
> ----------+---------------------------------
>       1294 | (I Can''t Get No) Satisfaction
>       1340 | (Hidden Track)
>       1503 | (Nice Dream)
>       1942 | (I) Get Lost
> (4 rows)
>
> intranet=# select track_name from ms_track where track_name ~ '^\(';
> ERROR:  invalid regular expression: parentheses () not balanced
> intranet=# select track_name from ms_track where track_name ~ '^(';
> ERROR:  invalid regular expression: parentheses () not balanced
> intranet=# select track_name from ms_track where track_name ~ '^\(';
> ERROR:  invalid regular expression: parentheses () not balanced
> ======================================================================
>
> Now I have tried a similar query using the PHP POSIX Regular Expressions
> and it accepts the sequence '^\(' and matches correctly. Is this a
> "feature" of PG that cannot be worked around easily?

You need to escape the backslash:

  select track_name from ms_track where track_name ~ '^\\
(';
--
Oliver Elphick                                          olly@lfix.co.uk
Isle of Wight                              http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA  92C8 39E7 280E 3631 3F0E  1EC0 5664 7A2F A543 10EA
                 ========================================
     "Be still before the LORD and wait patiently for him;
      do not fret when men succeed in their ways, when they
      carry out their wicked schemes."
                            Psalms 37:7