diff options
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/access/heap/pruneheap.c | 25 |
1 files changed, 8 insertions, 17 deletions
diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c index c7331d8108e..50ed76198c9 100644 --- a/src/backend/access/heap/pruneheap.c +++ b/src/backend/access/heap/pruneheap.c @@ -190,6 +190,12 @@ heap_page_prune_opt(Relation relation, Buffer buffer) /* And release buffer lock */ LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + + /* + * We avoid reuse of any free space created on the page by unrelated + * UPDATEs/INSERTs by opting to not update the FSM at this point. The + * free space should be reused by UPDATEs to *this* page. + */ } } @@ -197,7 +203,8 @@ heap_page_prune_opt(Relation relation, Buffer buffer) /* * Prune and repair fragmentation in the specified page. * - * Caller must have pin and buffer cleanup lock on the page. + * Caller must have pin and buffer cleanup lock on the page. Note that we + * don't update the FSM information for page on caller's behalf. * * vistest is used to distinguish whether tuples are DEAD or RECENTLY_DEAD * (see heap_prune_satisfies_vacuum and @@ -382,22 +389,6 @@ heap_page_prune(Relation relation, Buffer buffer, if (report_stats && ndeleted > prstate.ndead) pgstat_update_heap_dead_tuples(relation, ndeleted - prstate.ndead); - /* - * XXX Should we update the FSM information of this page ? - * - * There are two schools of thought here. We may not want to update FSM - * information so that the page is not used for unrelated UPDATEs/INSERTs - * and any free space in this page will remain available for further - * UPDATEs in *this* page, thus improving chances for doing HOT updates. - * - * But for a large table and where a page does not receive further UPDATEs - * for a long time, we might waste this space by not updating the FSM - * information. The relation may get extended and fragmented further. - * - * One possibility is to leave "fillfactor" worth of space in this page - * and update FSM with the remaining space. - */ - return ndeleted; } |