On Fri, Apr 12, 2013 at 8:44 AM, whiplash <whipl...@bss.org.ua> wrote:
> > CREATE UNIQUE INDEX idx_table0_unique > ON table0 ( field0, coalesce ( field1, 'INDEX_COLUMN_NULL' ) ); > > I created function for insert only unique record (part of code): > > BEGIN > INSERT INTO table0 ( field0, field1 ) VALUES ( p_field0, p_field1 ) > RETURNING id INTO v_table0_id; > EXCEPTION WHEN unique_violation THEN > SELECT id FROM table0 WHERE field0 = p_field0 AND field1 = p_field1; > END; > > I use this function for add data to table and sometimes I getting false > unique violation (in block above). Why? > if p_field1 is NULL, then the select cannot return any rows, but can still violate the constraint. Also, you may have a race, where the row exists when the insert was attempted, but was gone by the time it tried to do the select. Cheers, Jeff
