On 29/01/2012 16:06, p...@beccati.com wrote:
> The following bug has been logged on the website:
>
> Bug reference: 6416
> Logged by: Matteo Beccati
> Email address: p...@beccati.com
> PostgreSQL version: 9.1.2
> Operating system: Debian Sqeeze
> Description:
>
> I've just noticed that an expression index I've created was not used with a
> view contiaining a UNION ALL. Switching to UNION or querying the table
> directly works as expected.
>
> A self contained test case follows:
Sorry about the formatting issue. You will find it attached.
Cheers
--
Matteo Beccati
Development & Consulting - http://www.beccati.com/
regression=# CREATE FUNCTION ab(in text, in text, out ab text) AS $$BEGIN ab :=
$1 || $2; END;$$ LANGUAGE plpgsql IMMUTABLE;
CREATE FUNCTION
regression=# CREATE table t1 (a text, b text);
CREATE TABLE
regression=# CREATE INDEX t1_ab_idx on t1 (ab(a, b));
CREATE INDEX
regression=# CREATE table t2 (ab text primary key);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t2_pkey" for
table "t2"
CREATE TABLE
regression=# INSERT INTO t1 VALUES ('a', 'b');
INSERT 0 1
regression=# INSERT INTO t2 VALUES ('ab');
INSERT 0 1
regression=# VACUUM ANALYZE ;
VACUUM
regression=# SET enable_seqscan = false;
SET
regression=# EXPLAIN ANALYZE SELECT * FROM (SELECT ab(a, b) AS ab FROM t1 UNION
ALL SELECT * FROM t2) t WHERE ab = 'ab';
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------
Result (cost=10000000000.00..10000000009.53 rows=2 width=18) (actual
time=0.052..0.066 rows=2 loops=1)
-> Append (cost=10000000000.00..10000000009.53 rows=2 width=18) (actual
time=0.052..0.065 rows=2 loops=1)
-> Seq Scan on t1 (cost=10000000000.00..10000000001.26 rows=1
width=32) (actual time=0.051..0.052 rows=1 loops=1)
Filter: (ab(a, b) = 'ab'::text)
-> Index Scan using t2_pkey on t2 (cost=0.00..8.27 rows=1 width=3)
(actual time=0.010..0.011 rows=1 loops=1)
Index Cond: (ab = 'ab'::text)
Total runtime: 0.106 ms
(7 rows)
regression=# EXPLAIN ANALYZE SELECT * FROM (SELECT ab(a, b) AS ab FROM t1 UNION
SELECT * FROM t2) t WHERE ab = 'ab';
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------
Unique (cost=17.07..17.08 rows=2 width=4) (actual time=0.071..0.073 rows=1
loops=1)
-> Sort (cost=17.07..17.07 rows=2 width=4) (actual time=0.070..0.070
rows=2 loops=1)
Sort Key: (ab(t1.a, t1.b))
Sort Method: quicksort Memory: 25kB
-> Append (cost=0.25..17.06 rows=2 width=4) (actual
time=0.050..0.058 rows=2 loops=1)
-> Index Scan using t1_ab_idx on t1 (cost=0.25..8.77 rows=1
width=4) (actual time=0.049..0.050 rows=1 loops=1)
Index Cond: (ab(a, b) = 'ab'::text)
-> Index Scan using t2_pkey on t2 (cost=0.00..8.27 rows=1
width=3) (actual time=0.004..0.005 rows=1 loops=1)
Index Cond: (ab = 'ab'::text)
Total runtime: 0.116 ms
(10 rows)
regression=# EXPLAIN ANALYZE SELECT * FROM (SELECT ab(a, b) AS ab FROM t1) t
WHERE ab = 'ab';
QUERY PLAN
--------------------------------------------------------------------------------------------------------------
Index Scan using t1_ab_idx on t1 (cost=0.25..8.77 rows=1 width=4) (actual
time=0.030..0.032 rows=1 loops=1)
Index Cond: (ab(a, b) = 'ab'::text)
Total runtime: 0.048 ms
(3 rows)
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