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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
48 lines
1.3 KiB
SQL
48 lines
1.3 KiB
SQL
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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SELECT count(*) FROM tst WHERE t = '5';
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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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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EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE t = '5';
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EXPLAIN (COSTS OFF) SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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SELECT count(*) FROM tst WHERE i = 7;
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SELECT count(*) FROM tst WHERE t = '5';
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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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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SELECT count(*) FROM tst WHERE t = '5';
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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VACUUM FULL tst;
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SELECT count(*) FROM tst WHERE i = 7;
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SELECT count(*) FROM tst WHERE t = '5';
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SELECT count(*) FROM tst WHERE i = 7 AND t = '5';
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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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