Hi,
suppose, for simplicity, there is a table with index like this:
create table TABLE1 (
A integer
);
create index TABLE1_A on TABLE1 (A);
My question is: why psql (7.3.3) does not use index when filtering by A IS
NULL, A IS NOT
NULL expressions?
In fact, I need to filter by expression ((A is null) or (A > const)).
Is there a way to filter by this expression using index?
Functional index cannot be used (except strange solution with CASE-ing and
converting NULL values into some integer constant)
----------------------------------------------------------------------------
--
Index Scan using table1_a on table1 (cost=0.00..437.14 rows=29164 width=4)
Index Cond: (a > 1000)
----------------------------------------------------------------------------
--
Seq Scan on table1 (cost=0.00..448.22 rows=1 width=4)
Filter: (a IS NULL)
--------------------------------------------------------
Seq Scan on table1 (cost=0.00..448.22 rows=30222 width=4)
Filter: (a IS NOT NULL)
------------------------------------------------------------
Seq Scan on table1 (cost=0.00..523.77 rows=29164 width=4)
Filter: ((a IS NULL) OR (a > 1000))
------------------------------------------------------------
CH
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