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Keep all_frozen updated in heap_page_prune_and_freeze

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Previously, we relied on all_visible and all_frozen being used together
to ensure that all_frozen was correct, but it is better to keep both
fields updated.

Future changes will separate their usage, so we should not depend on
all_visible for the validity of all_frozen.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_ZMw6Npd_qm2KM%2BFwQ3cMOMx1Dh3VMhp8-V7SOLxdK9-g%40mail.gmail.com
This commit is contained in:
Melanie Plageman
2025-11-20 10:58:34 -05:00
parent 1937ed7062
commit 351d7e2441
2 changed files with 37 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

60
src/backend/access/heap/pruneheap.c
View File

@@ -143,10 +143,6 @@ typedef struct
* whether to freeze the page or not. The all_visible and all_frozen
* values returned to the caller are adjusted to include LP_DEAD items at
* the end.
*
* all_frozen should only be considered valid if all_visible is also set;
* we don't bother to clear the all_frozen flag every time we clear the
* all_visible flag.
*/
bool all_visible;
bool all_frozen;
@@ -359,8 +355,10 @@ heap_page_will_freeze(Relation relation, Buffer buffer,
* anymore. The opportunistic freeze heuristic must be improved;
* however, for now, try to approximate the old logic.
*/
if (prstate->all_visible && prstate->all_frozen && prstate->nfrozen > 0)
if (prstate->all_frozen && prstate->nfrozen > 0)
{
Assert(prstate->all_visible);
/*
* Freezing would make the page all-frozen. Have already emitted
* an FPI or will do so anyway?
@@ -544,9 +542,9 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
* dead tuples which are not yet removable. However, dead tuples which
* will be removed by the end of vacuuming should not preclude us from
* opportunistically freezing. Because of that, we do not clear
* all_visible when we see LP_DEAD items. We fix that at the end of the
* function, when we return the value to the caller, so that the caller
* doesn't set the VM bit incorrectly.
* all_visible and all_frozen when we see LP_DEAD items. We fix that at
* the end of the function, when we return the value to the caller, so
* that the caller doesn't set the VM bits incorrectly.
*/
if (prstate.attempt_freeze)
{
@@ -783,6 +781,8 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
do_hint_prune,
&prstate);
Assert(!prstate.all_frozen || prstate.all_visible);
/* Any error while applying the changes is critical */
START_CRIT_SECTION();
@@ -852,7 +852,7 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
*/
if (do_freeze)
{
if (prstate.all_visible && prstate.all_frozen)
if (prstate.all_frozen)
frz_conflict_horizon = prstate.visibility_cutoff_xid;
else
{
@@ -889,16 +889,16 @@ heap_page_prune_and_freeze(PruneFreezeParams *params,
presult->recently_dead_tuples = prstate.recently_dead_tuples;
/*
* It was convenient to ignore LP_DEAD items in all_visible earlier on to
* make the choice of whether or not to freeze the page unaffected by the
* short-term presence of LP_DEAD items. These LP_DEAD items were
* effectively assumed to be LP_UNUSED items in the making. It doesn't
* matter which vacuum heap pass (initial pass or final pass) ends up
* setting the page all-frozen, as long as the ongoing VACUUM does it.
* It was convenient to ignore LP_DEAD items in all_visible/all_frozen
* earlier on to make the choice of whether or not to freeze the page
* unaffected by the short-term presence of LP_DEAD items. These LP_DEAD
* items were effectively assumed to be LP_UNUSED items in the making. It
* doesn't matter which vacuum heap pass (initial pass or final pass) ends
* up setting the page all-frozen, as long as the ongoing VACUUM does it.
*
* Now that freezing has been finalized, unset all_visible if there are
* any LP_DEAD items on the page. It needs to reflect the present state
* of the page, as expected by our caller.
* Now that freezing has been finalized, unset all_visible and all_frozen
* if there are any LP_DEAD items on the page. It needs to reflect the
* present state of the page, as expected by our caller.
*/
if (prstate.all_visible && prstate.lpdead_items == 0)
{
@@ -1289,8 +1289,9 @@ heap_prune_record_dead(PruneState *prstate, OffsetNumber offnum,
prstate->ndead++;
/*
* Deliberately delay unsetting all_visible until later during pruning.
* Removable dead tuples shouldn't preclude freezing the page.
* Deliberately delay unsetting all_visible and all_frozen until later
* during pruning. Removable dead tuples shouldn't preclude freezing the
* page.
*/
/* Record the dead offset for vacuum */
@@ -1418,6 +1419,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
if (!HeapTupleHeaderXminCommitted(htup))
{
prstate->all_visible = false;
prstate->all_frozen = false;
break;
}
@@ -1432,14 +1434,15 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
/*
* For now always use prstate->cutoffs for this test, because
* we only update 'all_visible' when freezing is requested. We
* could use GlobalVisTestIsRemovableXid instead, if a
* non-freezing caller wanted to set the VM bit.
* we only update 'all_visible' and 'all_frozen' when freezing
* is requested. We could use GlobalVisTestIsRemovableXid
* instead, if a non-freezing caller wanted to set the VM bit.
*/
Assert(prstate->cutoffs);
if (!TransactionIdPrecedes(xmin, prstate->cutoffs->OldestXmin))
{
prstate->all_visible = false;
prstate->all_frozen = false;
break;
}
@@ -1453,6 +1456,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
case HEAPTUPLE_RECENTLY_DEAD:
prstate->recently_dead_tuples++;
prstate->all_visible = false;
prstate->all_frozen = false;
/*
* This tuple will soon become DEAD. Update the hint field so
@@ -1472,6 +1476,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
* does, so be consistent.
*/
prstate->all_visible = false;
prstate->all_frozen = false;
/*
* If we wanted to optimize for aborts, we might consider marking
@@ -1490,6 +1495,7 @@ heap_prune_record_unchanged_lp_normal(Page page, PruneState *prstate, OffsetNumb
*/
prstate->live_tuples++;
prstate->all_visible = false;
prstate->all_frozen = false;
/*
* This tuple may soon become DEAD. Update the hint field so that
@@ -1554,10 +1560,10 @@ heap_prune_record_unchanged_lp_dead(Page page, PruneState *prstate, OffsetNumber
* hastup/nonempty_pages as provisional no matter how LP_DEAD items are
* handled (handled here, or handled later on).
*
* Similarly, don't unset all_visible until later, at the end of
* heap_page_prune_and_freeze(). This will allow us to attempt to freeze
* the page after pruning. As long as we unset it before updating the
* visibility map, this will be correct.
* Similarly, don't unset all_visible and all_frozen until later, at the
* end of heap_page_prune_and_freeze(). This will allow us to attempt to
* freeze the page after pruning. As long as we unset it before updating
* the visibility map, this will be correct.
*/
/* Record the dead offset for vacuum */

9
src/backend/access/heap/vacuumlazy.c
View File

@@ -2017,7 +2017,6 @@ lazy_scan_prune(LVRelState *vacrel,
* agreement with heap_page_is_all_visible() using an assertion.
*/
#ifdef USE_ASSERT_CHECKING
/* Note that all_frozen value does not matter when !all_visible */
if (presult.all_visible)
{
TransactionId debug_cutoff;
@@ -2071,6 +2070,7 @@ lazy_scan_prune(LVRelState *vacrel,
*has_lpdead_items = (presult.lpdead_items > 0);
Assert(!presult.all_visible || !(*has_lpdead_items));
Assert(!presult.all_frozen || presult.all_visible);
/*
* Handle setting visibility map bit based on information from the VM (as
@@ -2176,11 +2176,10 @@ lazy_scan_prune(LVRelState *vacrel,
/*
* If the all-visible page is all-frozen but not marked as such yet, mark
* it as all-frozen. Note that all_frozen is only valid if all_visible is
* true, so we must check both all_visible and all_frozen.
* it as all-frozen.
*/
else if (all_visible_according_to_vm && presult.all_visible &&
presult.all_frozen && !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
else if (all_visible_according_to_vm && presult.all_frozen &&
!VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
{
uint8 old_vmbits;