On 10/2/07, Enrico Weigelt <weigelt@metux.de> wrote:
>
> Hi folks,
>
>
> I'm looking for some way to find broken regex'es in some column
> to kick them off. For now I'm regularily fetching all regexes
> from an PHP script, try an preg_match() and so find the broken
> ones to later remove them.
>
> Is there any way to do this directly within the db ?
Of course. Exceptions is what You need!
CREATE FUNCTION regex_is_broken(r text) RETURNS boolean AS $$ BEGIN PERFORM '' ~ r; RETURN 'f';
EXCEPTION WHEN INVALID_REGULAR_EXPRESSION THEN RETURN 't'; END;
$$ LANGUAGE PLpgSQL STRICT IMMUTABLE;
...and then you could do something like:
DELETE FROM table WHERE regex_is_broken(rx_col);
You don't need PLpgSQL to prevent such invalid regexes in the
first place. You could use CHECK constraint for it:
CREATE TABLE rx_check ( rx text CHECK ('' ~ rx IN ('t','f'))
);
postgres=> INSERT INTO rx_check (rx) VALUES ('.*');
INSERT 0 1
Time: 13.660 ms
postgres=> INSERT INTO rx_check (rx) VALUES ('234234');
INSERT 0 1
Time: 2.282 ms
postgres=> INSERT INTO rx_check (rx) VALUES ('par).*');
ERROR: invalid regular expression: parentheses () not balanced
Regards, Dawid
