|
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 |
|
3 | 3 | Heap Only Tuples (HOT) |
4 | 4 | ====================== |
@@ -246,6 +246,12 @@ scans reasonably sized, the maximum number of line pointers per page |
246 | 246 | is arbitrarily capped at MaxHeapTuplesPerPage (the most tuples that |
247 | 247 | could fit without HOT pruning). |
248 | 248 |
|
| 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 |
|
250 | 256 | VACUUM |
251 | 257 | ------ |
|