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CREATE EXTENSION bloom;
CREATE TABLE tst (
i int4,
t text
);
INSERT INTO tst SELECT i%10, substr(md5(i::text), 1, 1) FROM generate_series(1,100000) i;
CREATE INDEX bloomidx ON tst USING bloom (i, t) WITH (col1 = 3);
SET enable_seqscan=on;
SET enable_bitmapscan=off;
SET enable_indexscan=off;
SELECT count(*) FROM tst WHERE i = 7;
count
-------
10000
(1 row)
SELECT count(*) FROM tst WHERE t = '5';
count
-------
6264
(1 row)
SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
count
-------
588
(1 row)
SET enable_seqscan=off;
SET enable_bitmapscan=on;
SET enable_indexscan=on;
EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE i = 7;
QUERY PLAN
-------------------------------------------
Aggregate
-> Bitmap Heap Scan on tst
Recheck Cond: (i = 7)
-> Bitmap Index Scan on bloomidx
Index Cond: (i = 7)
(5 rows)
EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE t = '5';
QUERY PLAN
-------------------------------------------
Aggregate
-> Bitmap Heap Scan on tst
Recheck Cond: (t = '5'::text)
-> Bitmap Index Scan on bloomidx
Index Cond: (t = '5'::text)
(5 rows)
EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
QUERY PLAN
---------------------------------------------------------
Aggregate
-> Bitmap Heap Scan on tst
Recheck Cond: ((i = 7) AND (t = '5'::text))
-> Bitmap Index Scan on bloomidx
Index Cond: ((i = 7) AND (t = '5'::text))
(5 rows)
SELECT count(*) FROM tst WHERE i = 7;
count
-------
10000
(1 row)
SELECT count(*) FROM tst WHERE t = '5';
count
-------
6264
(1 row)
SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
count
-------
588
(1 row)
DELETE FROM tst;
INSERT INTO tst SELECT i%10, substr(md5(i::text), 1, 1) FROM generate_series(1,100000) i;
VACUUM ANALYZE tst;
SELECT count(*) FROM tst WHERE i = 7;
count
-------
10000
(1 row)
SELECT count(*) FROM tst WHERE t = '5';
count
-------
6264
(1 row)
SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
count
-------
588
(1 row)
VACUUM FULL tst;
SELECT count(*) FROM tst WHERE i = 7;
count
-------
10000
(1 row)
SELECT count(*) FROM tst WHERE t = '5';
count
-------
6264
(1 row)
SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
count
-------
588
(1 row)
RESET enable_seqscan;
RESET enable_bitmapscan;
RESET enable_indexscan;
|
