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Count pages set all-visible and all-frozen in VM during vacuum

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Heap vacuum already counts and logs pages with newly frozen tuples. Now
count and log the number of pages newly set all-visible and all-frozen
in the visibility map.

Pages that are all-visible but not all-frozen are debt for future
aggressive vacuums. The counts of newly all-visible and all-frozen pages
give us insight into the rate at which this debt is being accrued and
paid down.

Author: Melanie Plageman
Reviewed-by: Masahiko Sawada, Alastair Turner, Nitin Jadhav, Andres Freund, Bilal Yavuz, Tomas Vondra
Discussion: https://postgr.es/m/flat/CAAKRu_ZQe26xdvAqo4weHLR%3DivQ8J4xrSfDDD8uXnh-O-6P6Lg%40mail.gmail.com#6d8d2b4219394f774889509bf3bdc13d,
https://postgr.es/m/ctdjzroezaxmiyah3gwbwm67defsrwj2b5fpfs4ku6msfpxeia%40mwjyqlhwr2wu
This commit is contained in:
Melanie Plageman 2024-12-17 14:13:27 -05:00
parent 4b565a198b
commit dc6acfd910
1 changed files with 111 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

123
src/backend/access/heap/vacuumlazy.c
View File

@ -189,6 +189,21 @@ typedef struct LVRelState
BlockNumber scanned_pages; /* # pages examined (not skipped via VM) */
BlockNumber removed_pages; /* # pages removed by relation truncation */
BlockNumber new_frozen_tuple_pages; /* # pages with newly frozen tuples */
/* # pages newly set all-visible in the VM */
BlockNumber vm_new_visible_pages;
/*
* # pages newly set all-visible and all-frozen in the VM. This is a
* subset of vm_new_visible_pages. That is, vm_new_visible_pages includes
* all pages set all-visible, but vm_new_visible_frozen_pages includes
* only those which were also set all-frozen.
*/
BlockNumber vm_new_visible_frozen_pages;
/* # all-visible pages newly set all-frozen in the VM */
BlockNumber vm_new_frozen_pages;
BlockNumber lpdead_item_pages; /* # pages with LP_DEAD items */
BlockNumber missed_dead_pages; /* # pages with missed dead tuples */
BlockNumber nonempty_pages; /* actually, last nonempty page + 1 */
@ -428,6 +443,10 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
vacrel->recently_dead_tuples = 0;
vacrel->missed_dead_tuples = 0;
vacrel->vm_new_visible_pages = 0;
vacrel->vm_new_visible_frozen_pages = 0;
vacrel->vm_new_frozen_pages = 0;
/*
* Get cutoffs that determine which deleted tuples are considered DEAD,
* not just RECENTLY_DEAD, and which XIDs/MXIDs to freeze. Then determine
@ -701,6 +720,13 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
100.0 * vacrel->new_frozen_tuple_pages /
orig_rel_pages,
(long long) vacrel->tuples_frozen);
appendStringInfo(&buf,
_("visibility map: %u pages set all-visible, %u pages set all-frozen (%u were all-visible)\n"),
vacrel->vm_new_visible_pages,
vacrel->vm_new_visible_frozen_pages +
vacrel->vm_new_frozen_pages,
vacrel->vm_new_frozen_pages);
if (vacrel->do_index_vacuuming)
{
if (vacrel->nindexes == 0 || vacrel->num_index_scans == 0)
@ -1354,6 +1380,8 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno,
*/
if (!PageIsAllVisible(page))
{
uint8 old_vmbits;
START_CRIT_SECTION();
/* mark buffer dirty before writing a WAL record */
@ -1373,10 +1401,24 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno,
log_newpage_buffer(buf, true);
PageSetAllVisible(page);
visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId,
VISIBILITYMAP_ALL_VISIBLE | VISIBILITYMAP_ALL_FROZEN);
old_vmbits = visibilitymap_set(vacrel->rel, blkno, buf,
InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId,
VISIBILITYMAP_ALL_VISIBLE |
VISIBILITYMAP_ALL_FROZEN);
END_CRIT_SECTION();
/*
* If the page wasn't already set all-visible and/or all-frozen in
* the VM, count it as newly set for logging.
*/
if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
{
vacrel->vm_new_visible_pages++;
vacrel->vm_new_visible_frozen_pages++;
}
else if ((old_vmbits & VISIBILITYMAP_ALL_FROZEN) == 0)
vacrel->vm_new_frozen_pages++;
}
freespace = PageGetHeapFreeSpace(page);
@ -1531,6 +1573,7 @@ lazy_scan_prune(LVRelState *vacrel,
*/
if (!all_visible_according_to_vm && presult.all_visible)
{
uint8 old_vmbits;
uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
if (presult.all_frozen)
@ -1554,9 +1597,24 @@ lazy_scan_prune(LVRelState *vacrel,
*/
PageSetAllVisible(page);
MarkBufferDirty(buf);
visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, presult.vm_conflict_horizon,
flags);
old_vmbits = visibilitymap_set(vacrel->rel, blkno, buf,
InvalidXLogRecPtr,
vmbuffer, presult.vm_conflict_horizon,
flags);
/*
* If the page wasn't already set all-visible and/or all-frozen in the
* VM, count it as newly set for logging.
*/
if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
{
vacrel->vm_new_visible_pages++;
if (presult.all_frozen)
vacrel->vm_new_visible_frozen_pages++;
}
else if ((old_vmbits & VISIBILITYMAP_ALL_FROZEN) == 0 &&
presult.all_frozen)
vacrel->vm_new_frozen_pages++;
}
/*
@ -1606,6 +1664,8 @@ lazy_scan_prune(LVRelState *vacrel,
else if (all_visible_according_to_vm && presult.all_visible &&
presult.all_frozen && !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
{
uint8 old_vmbits;
/*
* Avoid relying on all_visible_according_to_vm as a proxy for the
* page-level PD_ALL_VISIBLE bit being set, since it might have become
@ -1625,10 +1685,31 @@ lazy_scan_prune(LVRelState *vacrel,
* was logged when the page's tuples were frozen.
*/
Assert(!TransactionIdIsValid(presult.vm_conflict_horizon));
visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId,
VISIBILITYMAP_ALL_VISIBLE |
VISIBILITYMAP_ALL_FROZEN);
old_vmbits = visibilitymap_set(vacrel->rel, blkno, buf,
InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId,
VISIBILITYMAP_ALL_VISIBLE |
VISIBILITYMAP_ALL_FROZEN);
/*
* The page was likely already set all-visible in the VM. However,
* there is a small chance that it was modified sometime between
* setting all_visible_according_to_vm and checking the visibility
* during pruning. Check the return value of old_vmbits anyway to
* ensure the visibility map counters used for logging are accurate.
*/
if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
{
vacrel->vm_new_visible_pages++;
vacrel->vm_new_visible_frozen_pages++;
}
/*
* We already checked that the page was not set all-frozen in the VM
* above, so we don't need to test the value of old_vmbits.
*/
else
vacrel->vm_new_frozen_pages++;
}
}
@ -2274,6 +2355,7 @@ lazy_vacuum_heap_page(LVRelState *vacrel, BlockNumber blkno, Buffer buffer,
if (heap_page_is_all_visible(vacrel, buffer, &visibility_cutoff_xid,
&all_frozen))
{
uint8 old_vmbits;
uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
if (all_frozen)
@ -2283,8 +2365,25 @@ lazy_vacuum_heap_page(LVRelState *vacrel, BlockNumber blkno, Buffer buffer,
}
PageSetAllVisible(page);
visibilitymap_set(vacrel->rel, blkno, buffer, InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid, flags);
old_vmbits = visibilitymap_set(vacrel->rel, blkno, buffer,
InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid,
flags);
/*
* If the page wasn't already set all-visible and/or all-frozen in the
* VM, count it as newly set for logging.
*/
if ((old_vmbits & VISIBILITYMAP_ALL_VISIBLE) == 0)
{
vacrel->vm_new_visible_pages++;
if (all_frozen)
vacrel->vm_new_visible_frozen_pages++;
}
else if ((old_vmbits & VISIBILITYMAP_ALL_FROZEN) == 0 &&
all_frozen)
vacrel->vm_new_frozen_pages++;
}
/* Revert to the previous phase information for error traceback */