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1 |
| -$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.6 2010/04/23 23:21:44rhaas Exp $ |
| 1 | +$PostgreSQL: pgsql/src/backend/access/heap/README.HOT,v 1.7 2010/09/19 17:51:44momjian Exp $ |
2 | 2 |
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3 | 3 | Heap Only Tuples (HOT)
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4 | 4 | ======================
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@@ -246,6 +246,12 @@ scans reasonably sized, the maximum number of line pointers per page
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246 | 246 | is arbitrarily capped at MaxHeapTuplesPerPage (the most tuples that
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247 | 247 | could fit without HOT pruning).
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248 | 248 |
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| 249 | +Effectively, space reclamation happens during tuple retrieval when the |
| 250 | +page is nearly full (<10% free) and a buffer cleanup lock can be |
| 251 | +acquired. This means that UPDATE, DELETE, and SELECT can trigger space |
| 252 | +reclamation, but often not during INSERT ... VALUES because it does |
| 253 | +not retrieve a row. |
| 254 | + |
249 | 255 |
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250 | 256 | VACUUM
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251 | 257 | ------
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