diff options
Diffstat (limited to 'src/backend/storage/freespace/README')
| -rw-r--r-- | src/backend/storage/freespace/README | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/src/backend/storage/freespace/README b/src/backend/storage/freespace/README index bbd1b93fac6..e7ff23b76f7 100644 --- a/src/backend/storage/freespace/README +++ b/src/backend/storage/freespace/README @@ -180,13 +180,13 @@ have a corrupted page, with a parent somewhere with too small a value. Secondly, if we detect corrupted pages while we search, traversing down the tree. That check will notice if a parent node is set to too high a value. In both cases, the upper nodes on the page are immediately rebuilt, fixing -the corruption. +the corruption so far as that page is concerned. -Vacuum updates all the bottom level pages with correct amount of free space -on the heap pages, fixing any outdated values there. After the heap and -index passes are done, FreeSpaceMapVacuum is called, and the FSM tree is -scanned in depth-first order. This fixes any discrepancies between upper -and lower level FSM pages. +VACUUM updates all the bottom-level FSM pages with the correct amount of free +space on corresponding heap pages, as it proceeds through the heap. This +goes through fsm_set_avail(), so that the upper nodes on those pages are +immediately updated. Periodically, VACUUM calls FreeSpaceMapVacuum[Range] +to propagate the new free-space info into the upper pages of the FSM tree. TODO ---- |