Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit42f9427

Browse files
Update heap_page_prune() free space map comments.
It is up to the heap_page_prune() caller to decide what to do aboutupdating the FSM for a page following pruning. Update old comments thataddress what we might want to do as if it was the responsibility ofheap_page_prune() itself. heap_page_prune() doesn't have enoughhigh-level context to make a sensible choice.
1 parenteb9baef commit42f9427

File tree

1 file changed

+8
-17
lines changed

1 file changed

+8
-17
lines changed

‎src/backend/access/heap/pruneheap.c

Lines changed: 8 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -190,14 +190,21 @@ heap_page_prune_opt(Relation relation, Buffer buffer)
190190

191191
/* And release buffer lock */
192192
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
193+
194+
/*
195+
* We avoid reuse of any free space created on the page by unrelated
196+
* UPDATEs/INSERTs by opting to not update the FSM at this point. The
197+
* free space should be reused by UPDATEs to *this* page.
198+
*/
193199
}
194200
}
195201

196202

197203
/*
198204
* Prune and repair fragmentation in the specified page.
199205
*
200-
* Caller must have pin and buffer cleanup lock on the page.
206+
* Caller must have pin and buffer cleanup lock on the page. Note that we
207+
* don't update the FSM information for page on caller's behalf.
201208
*
202209
* vistest is used to distinguish whether tuples are DEAD or RECENTLY_DEAD
203210
* (see heap_prune_satisfies_vacuum and
@@ -382,22 +389,6 @@ heap_page_prune(Relation relation, Buffer buffer,
382389
if (report_stats&&ndeleted>prstate.ndead)
383390
pgstat_update_heap_dead_tuples(relation,ndeleted-prstate.ndead);
384391

385-
/*
386-
* XXX Should we update the FSM information of this page ?
387-
*
388-
* There are two schools of thought here. We may not want to update FSM
389-
* information so that the page is not used for unrelated UPDATEs/INSERTs
390-
* and any free space in this page will remain available for further
391-
* UPDATEs in *this* page, thus improving chances for doing HOT updates.
392-
*
393-
* But for a large table and where a page does not receive further UPDATEs
394-
* for a long time, we might waste this space by not updating the FSM
395-
* information. The relation may get extended and fragmented further.
396-
*
397-
* One possibility is to leave "fillfactor" worth of space in this page
398-
* and update FSM with the remaining space.
399-
*/
400-
401392
returnndeleted;
402393
}
403394

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp