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e6858e6657
Add a column pg_class.relallvisible to remember the number of pages that were all-visible according to the visibility map as of the last VACUUM (or ANALYZE, or some other operations that update pg_class.relpages). Use relallvisible/relpages, instead of an arbitrary constant, to estimate how many heap page fetches can be avoided during an index-only scan. This is pretty primitive and will no doubt see refinements once we've acquired more field experience with the index-only scan mechanism, but it's way better than using a constant. Note: I had to adjust an underspecified query in the window.sql regression test, because it was changing answers when the plan changed to use an index-only scan. Some of the adjacent tests perhaps should be adjusted as well, but I didn't do that here.
34 lines
1.1 KiB
C
34 lines
1.1 KiB
C
/*-------------------------------------------------------------------------
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*
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* visibilitymap.h
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* visibility map interface
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*
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*
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* Portions Copyright (c) 2007-2011, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/visibilitymap.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef VISIBILITYMAP_H
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#define VISIBILITYMAP_H
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#include "access/xlogdefs.h"
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#include "storage/block.h"
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#include "storage/buf.h"
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#include "utils/relcache.h"
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extern void visibilitymap_clear(Relation rel, BlockNumber heapBlk,
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Buffer vmbuf);
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extern void visibilitymap_pin(Relation rel, BlockNumber heapBlk,
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Buffer *vmbuf);
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extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
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extern void visibilitymap_set(Relation rel, BlockNumber heapBlk,
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XLogRecPtr recptr, Buffer vmbuf);
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extern bool visibilitymap_test(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
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extern BlockNumber visibilitymap_count(Relation rel);
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extern void visibilitymap_truncate(Relation rel, BlockNumber nheapblocks);
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#endif /* VISIBILITYMAP_H */
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