Re: Index on a NULL-value

[Tobias Brox - Tue at 11:02:07AM +0800]
> test=# explain select * from mock where b is NULL;
> QUERY PLAN
> --------------------------------------------------------------------
> Seq Scan on mock (cost=100000000.00..100000020.00 rows=6 width=8)
> Filter: (b IS NULL)
> (2 rows)

(...)

> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
> joining column's datatypes do not match

That tip helped me :-)

test=# explain select * from mock where (b IS NULL)=true;
QUERY PLAN

----------------------------------------------------------------------
Index Scan using b_is_null on mock (cost=0.00..4.68 rows=1 width=8)
Index Cond: ((b IS NULL) = true)
(2 rows)

--
Tobias Brox, Beijing