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Postgres FD Implementation
Commit cecde975 authored by Bruce Momjian's avatar Bruce Momjian
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Update HOT README about when single-page vacuums happen.

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