Update HOT README about when single-page vacuums happen.
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$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.6 2010/04/23 23:21:44 rhaas Exp $
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$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.7 2010/09/19 17:51:44 momjian Exp $
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Heap Only Tuples (HOT)
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Heap Only Tuples (HOT)
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======================
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======================
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@ -246,6 +246,12 @@ scans reasonably sized, the maximum number of line pointers per page
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is arbitrarily capped at MaxHeapTuplesPerPage (the most tuples that
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is arbitrarily capped at MaxHeapTuplesPerPage (the most tuples that
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could fit without HOT pruning).
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could fit without HOT pruning).
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Effectively, space reclamation happens during tuple retrieval when the
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page is nearly full (<10% free) and a buffer cleanup lock can be
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acquired. This means that UPDATE, DELETE, and SELECT can trigger space
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reclamation, but often not during INSERT ... VALUES because it does
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not retrieve a row.
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VACUUM
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VACUUM
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------
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------
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