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9ee014fc89
Module provides new access method. It is actually a simple Bloom filter implemented as pgsql's index. It could give some benefits on search with large number of columns. Module is a single way to test generic WAL interface committed earlier. Author: Teodor Sigaev, Alexander Korotkov Reviewers: Aleksander Alekseev, Michael Paquier, Jim Nasby
123 lines
2.4 KiB
Plaintext
123 lines
2.4 KiB
Plaintext
CREATE EXTENSION bloom;
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CREATE TABLE tst (
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i int4,
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t text
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);
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INSERT INTO tst SELECT i%10, substr(md5(i::text), 1, 1) FROM generate_series(1,100000) i;
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CREATE INDEX bloomidx ON tst USING bloom (i, t) WITH (col1 = 3);
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SET enable_seqscan=on;
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SET enable_bitmapscan=off;
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SET enable_indexscan=off;
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SELECT count(*) FROM tst WHERE i = 7;
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count
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-------
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10000
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(1 row)
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SELECT count(*) FROM tst WHERE t = '5';
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count
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-------
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6264
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(1 row)
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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count
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-------
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588
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(1 row)
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SET enable_seqscan=off;
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SET enable_bitmapscan=on;
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SET enable_indexscan=on;
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EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE i = 7;
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QUERY PLAN
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-------------------------------------------
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Aggregate
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-> Bitmap Heap Scan on tst
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Recheck Cond: (i = 7)
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-> Bitmap Index Scan on bloomidx
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Index Cond: (i = 7)
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(5 rows)
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EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE t = '5';
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QUERY PLAN
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-------------------------------------------
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Aggregate
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-> Bitmap Heap Scan on tst
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Recheck Cond: (t = '5'::text)
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-> Bitmap Index Scan on bloomidx
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Index Cond: (t = '5'::text)
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(5 rows)
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EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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QUERY PLAN
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---------------------------------------------------------
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Aggregate
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-> Bitmap Heap Scan on tst
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Recheck Cond: ((i = 7) AND (t = '5'::text))
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-> Bitmap Index Scan on bloomidx
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Index Cond: ((i = 7) AND (t = '5'::text))
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(5 rows)
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SELECT count(*) FROM tst WHERE i = 7;
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count
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-------
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10000
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(1 row)
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SELECT count(*) FROM tst WHERE t = '5';
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count
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-------
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6264
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(1 row)
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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count
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-------
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588
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(1 row)
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DELETE FROM tst;
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INSERT INTO tst SELECT i%10, substr(md5(i::text), 1, 1) FROM generate_series(1,100000) i;
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VACUUM ANALYZE tst;
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SELECT count(*) FROM tst WHERE i = 7;
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count
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-------
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10000
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(1 row)
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SELECT count(*) FROM tst WHERE t = '5';
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count
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-------
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6264
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(1 row)
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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count
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-------
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588
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(1 row)
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VACUUM FULL tst;
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SELECT count(*) FROM tst WHERE i = 7;
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count
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-------
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10000
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(1 row)
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SELECT count(*) FROM tst WHERE t = '5';
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count
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-------
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6264
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(1 row)
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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count
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-------
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588
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(1 row)
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RESET enable_seqscan;
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RESET enable_bitmapscan;
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RESET enable_indexscan;
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