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4e82a95476
indexscan always occurs in one call, and the results are returned in a TIDBitmap instead of a limited-size array of TIDs. This should improve speed a little by reducing AM entry/exit overhead, and it is necessary infrastructure if we are ever to support bitmap indexes. In an only slightly related change, add support for TIDBitmaps to preserve (somewhat lossily) the knowledge that particular TIDs reported by an index need to have their quals rechecked when the heap is visited. This facility is not really used yet; we'll need to extend the forced-recheck feature to plain indexscans before it's useful, and that hasn't been coded yet. The intent is to use it to clean up 8.3's horrid @@@ kluge for text search with weighted queries. There might be other uses in future, but that one alone is sufficient reason. Heikki Linnakangas, with some adjustments by me.
42 lines
1.3 KiB
SQL
42 lines
1.3 KiB
SQL
-- Test bitmap AND and OR
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-- Generate enough data that we can test the lossy bitmaps.
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-- There's 55 tuples per page in the table. 53 is just
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-- below 55, so that an index scan with qual a = constant
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-- will return at least one hit per page. 59 is just above
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-- 55, so that an index scan with qual b = constant will return
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-- hits on most but not all pages. 53 and 59 are prime, so that
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-- there's a maximum number of a,b combinations in the table.
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-- That allows us to test all the different combinations of
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-- lossy and non-lossy pages with the minimum amount of data
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CREATE TABLE bmscantest (a int, b int, t text);
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INSERT INTO bmscantest
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SELECT (r%53), (r%59), 'foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo'
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FROM generate_series(1,70000) r;
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CREATE INDEX i_bmtest_a ON bmscantest(a);
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CREATE INDEX i_bmtest_b ON bmscantest(b);
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-- We want to use bitmapscans. With default settings, the planner currently
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-- chooses a bitmap scan for the queries below anyway, but let's make sure.
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set enable_indexscan=false;
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set enable_seqscan=false;
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-- Lower work_mem to trigger use of lossy bitmaps
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set work_mem = 64;
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-- Test bitmap-and.
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SELECT count(*) FROM bmscantest WHERE a = 1 AND b = 1;
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-- Test bitmap-or.
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SELECT count(*) FROM bmscantest WHERE a = 1 OR b = 1;
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-- clean up
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DROP TABLE bmscantest;
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