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Combine freezing and pruning steps in VACUUM

Browse Source 
Execute both freezing and pruning of tuples in the same
heap_page_prune() function, now called heap_page_prune_and_freeze(),
and emit a single WAL record containing all changes. That reduces the
overall amount of WAL generated.

This moves the freezing logic from vacuumlazy.c to the
heap_page_prune_and_freeze() function. The main difference in the
coding is that in vacuumlazy.c, we looked at the tuples after the
pruning had already happened, but in heap_page_prune_and_freeze() we
operate on the tuples before pruning. The heap_prepare_freeze_tuple()
function is now invoked after we have determined that a tuple is not
going to be pruned away.

VACUUM no longer needs to loop through the items on the page after
pruning. heap_page_prune_and_freeze() does all the work. It now
returns the list of dead offsets, including existing LP_DEAD items, to
the caller. Similarly it's now responsible for tracking 'all_visible',
'all_frozen', and 'hastup' on the caller's behalf.

Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/20240330055710.kqg6ii2cdojsxgje@liskov
This commit is contained in:
Heikki Linnakangas 2024-04-03 19:32:28 +03:00
parent 26d138f644
commit 6dbb490261
7 changed files with 813 additions and 545 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
src/backend/access/heap/heapam.c
View File

@ -6447,9 +6447,9 @@ FreezeMultiXactId(MultiXactId multi, uint16 t_infomask,
* XIDs or MultiXactIds that will need to be processed by a future VACUUM.
*
* VACUUM caller must assemble HeapTupleFreeze freeze plan entries for every
* tuple that we returned true for, and call heap_freeze_execute_prepared to
* execute freezing. Caller must initialize pagefrz fields for page as a
* whole before first call here for each heap page.
* tuple that we returned true for, and then execute freezing. Caller must
* initialize pagefrz fields for page as a whole before first call here for
* each heap page.
*
* VACUUM caller decides on whether or not to freeze the page as a whole.
* We'll often prepare freeze plans for a page that caller just discards.
@ -6765,35 +6765,19 @@ heap_execute_freeze_tuple(HeapTupleHeader tuple, HeapTupleFreeze *frz)
}
/*
* heap_freeze_execute_prepared
* Perform xmin/xmax XID status sanity checks before actually executing freeze
* plans.
*
* Executes freezing of one or more heap tuples on a page on behalf of caller.
* Caller passes an array of tuple plans from heap_prepare_freeze_tuple.
* Caller must set 'offset' in each plan for us. Note that we destructively
* sort caller's tuples array in-place, so caller had better be done with it.
*
* WAL-logs the changes so that VACUUM can advance the rel's relfrozenxid
* later on without any risk of unsafe pg_xact lookups, even following a hard
* crash (or when querying from a standby). We represent freezing by setting
* infomask bits in tuple headers, but this shouldn't be thought of as a hint.
* See section on buffer access rules in src/backend/storage/buffer/README.
* heap_prepare_freeze_tuple doesn't perform these checks directly because
* pg_xact lookups are relatively expensive. They shouldn't be repeated by
* successive VACUUMs that each decide against freezing the same page.
*/
void
heap_freeze_execute_prepared(Relation rel, Buffer buffer,
TransactionId snapshotConflictHorizon,
HeapTupleFreeze *tuples, int ntuples)
heap_pre_freeze_checks(Buffer buffer,
HeapTupleFreeze *tuples, int ntuples)
{
Page page = BufferGetPage(buffer);
Assert(ntuples > 0);
/*
* Perform xmin/xmax XID status sanity checks before critical section.
*
* heap_prepare_freeze_tuple doesn't perform these checks directly because
* pg_xact lookups are relatively expensive. They shouldn't be repeated
* by successive VACUUMs that each decide against freezing the same page.
*/
for (int i = 0; i < ntuples; i++)
{
HeapTupleFreeze *frz = tuples + i;
@ -6832,8 +6816,19 @@ heap_freeze_execute_prepared(Relation rel, Buffer buffer,
xmax)));
}
}
}
START_CRIT_SECTION();
/*
* Helper which executes freezing of one or more heap tuples on a page on
* behalf of caller. Caller passes an array of tuple plans from
* heap_prepare_freeze_tuple. Caller must set 'offset' in each plan for us.
* Must be called in a critical section that also marks the buffer dirty and,
* if needed, emits WAL.
*/
void
heap_freeze_prepared_tuples(Buffer buffer, HeapTupleFreeze *tuples, int ntuples)
{
Page page = BufferGetPage(buffer);
for (int i = 0; i < ntuples; i++)
{
@ -6844,22 +6839,6 @@ heap_freeze_execute_prepared(Relation rel, Buffer buffer,
htup = (HeapTupleHeader) PageGetItem(page, itemid);
heap_execute_freeze_tuple(htup, frz);
}
MarkBufferDirty(buffer);
/* Now WAL-log freezing if necessary */
if (RelationNeedsWAL(rel))
{
log_heap_prune_and_freeze(rel, buffer, snapshotConflictHorizon,
false, /* no cleanup lock required */
PRUNE_VACUUM_SCAN,
tuples, ntuples,
NULL, 0, /* redirected */
NULL, 0, /* dead */
NULL, 0); /* unused */
}
END_CRIT_SECTION();
}
/*

2
src/backend/access/heap/heapam_handler.c
View File

@ -1122,7 +1122,7 @@ heapam_scan_analyze_next_tuple(TableScanDesc scan, TransactionId OldestXmin,
* We ignore unused and redirect line pointers. DEAD line pointers
* should be counted as dead, because we need vacuum to run to get rid
* of them. Note that this rule agrees with the way that
* heap_page_prune() counts things.
* heap_page_prune_and_freeze() counts things.
*/
if (!ItemIdIsNormal(itemid))
{

763
src/backend/access/heap/pruneheap.c
View File

File diff suppressed because it is too large Load Diff

435
src/backend/access/heap/vacuumlazy.c
View File

@ -46,6 +46,7 @@
#include "commands/dbcommands.h"
#include "commands/progress.h"
#include "commands/vacuum.h"
#include "common/int.h"
#include "executor/instrument.h"
#include "miscadmin.h"
#include "pgstat.h"
@ -439,12 +440,13 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
* as an upper bound on the XIDs stored in the pages we'll actually scan
* (NewRelfrozenXid tracking must never be allowed to miss unfrozen XIDs).
*
* Next acquire vistest, a related cutoff that's used in heap_page_prune.
* We expect vistest will always make heap_page_prune remove any deleted
* tuple whose xmax is < OldestXmin. lazy_scan_prune must never become
* confused about whether a tuple should be frozen or removed. (In the
* future we might want to teach lazy_scan_prune to recompute vistest from
* time to time, to increase the number of dead tuples it can prune away.)
* Next acquire vistest, a related cutoff that's used in pruning. We
* expect vistest will always make heap_page_prune_and_freeze() remove any
* deleted tuple whose xmax is < OldestXmin. lazy_scan_prune must never
* become confused about whether a tuple should be frozen or removed. (In
* the future we might want to teach lazy_scan_prune to recompute vistest
* from time to time, to increase the number of dead tuples it can prune
* away.)
*/
vacrel->aggressive = vacuum_get_cutoffs(rel, params, &vacrel->cutoffs);
vacrel->rel_pages = orig_rel_pages = RelationGetNumberOfBlocks(rel);
@ -1382,27 +1384,18 @@ lazy_scan_new_or_empty(LVRelState *vacrel, Buffer buf, BlockNumber blkno,
return false;
}
/* qsort comparator for sorting OffsetNumbers */
static int
cmpOffsetNumbers(const void *a, const void *b)
{
return pg_cmp_u16(*(const OffsetNumber *) a, *(const OffsetNumber *) b);
}
/*
* lazy_scan_prune() -- lazy_scan_heap() pruning and freezing.
*
* Caller must hold pin and buffer cleanup lock on the buffer.
*
* Prior to PostgreSQL 14 there were very rare cases where heap_page_prune()
* was allowed to disagree with our HeapTupleSatisfiesVacuum() call about
* whether or not a tuple should be considered DEAD. This happened when an
* inserting transaction concurrently aborted (after our heap_page_prune()
* call, before our HeapTupleSatisfiesVacuum() call). There was rather a lot
* of complexity just so we could deal with tuples that were DEAD to VACUUM,
* but nevertheless were left with storage after pruning.
*
* As of Postgres 17, we circumvent this problem altogether by reusing the
* result of heap_page_prune()'s visibility check. Without the second call to
* HeapTupleSatisfiesVacuum(), there is no new HTSV_Result and there can be no
* disagreement. We'll just handle such tuples as if they had become fully dead
* right after this operation completes instead of in the middle of it. Note that
* any tuple that becomes dead after the call to heap_page_prune() can't need to
* be frozen, because it was visible to another session when vacuum started.
*
* vmbuffer is the buffer containing the VM block with visibility information
* for the heap block, blkno. all_visible_according_to_vm is the saved
* visibility status of the heap block looked up earlier by the caller. We
@ -1421,330 +1414,46 @@ lazy_scan_prune(LVRelState *vacrel,
bool *has_lpdead_items)
{
Relation rel = vacrel->rel;
OffsetNumber offnum,
maxoff;
ItemId itemid;
PruneResult presult;
int tuples_frozen,
lpdead_items,
live_tuples,
recently_dead_tuples;
HeapPageFreeze pagefrz;
bool hastup = false;
bool all_visible,
all_frozen;
TransactionId visibility_cutoff_xid;
PruneFreezeResult presult;
int prune_options = 0;
int64 fpi_before = pgWalUsage.wal_fpi;
OffsetNumber deadoffsets[MaxHeapTuplesPerPage];
HeapTupleFreeze frozen[MaxHeapTuplesPerPage];
Assert(BufferGetBlockNumber(buf) == blkno);
/*
* maxoff might be reduced following line pointer array truncation in
* heap_page_prune. That's safe for us to ignore, since the reclaimed
* space will continue to look like LP_UNUSED items below.
*/
maxoff = PageGetMaxOffsetNumber(page);
/* Initialize (or reset) page-level state */
pagefrz.freeze_required = false;
pagefrz.FreezePageRelfrozenXid = vacrel->NewRelfrozenXid;
pagefrz.FreezePageRelminMxid = vacrel->NewRelminMxid;
pagefrz.NoFreezePageRelfrozenXid = vacrel->NewRelfrozenXid;
pagefrz.NoFreezePageRelminMxid = vacrel->NewRelminMxid;
tuples_frozen = 0;
lpdead_items = 0;
live_tuples = 0;
recently_dead_tuples = 0;
/*
* Prune all HOT-update chains in this page.
*
* We count the number of tuples removed from the page by the pruning step
* in presult.ndeleted. It should not be confused with lpdead_items;
* lpdead_items's final value can be thought of as the number of tuples
* that were deleted from indexes.
* Prune all HOT-update chains and potentially freeze tuples on this page.
*
* If the relation has no indexes, we can immediately mark would-be dead
* items LP_UNUSED.
*/
prune_options = 0;
if (vacrel->nindexes == 0)
prune_options = HEAP_PAGE_PRUNE_MARK_UNUSED_NOW;
heap_page_prune(rel, buf, vacrel->vistest, prune_options,
&presult, PRUNE_VACUUM_SCAN, &vacrel->offnum);
/*
* We will update the VM after collecting LP_DEAD items and freezing
* tuples. Keep track of whether or not the page is all_visible and
* all_frozen and use this information to update the VM. all_visible
* implies 0 lpdead_items, but don't trust all_frozen result unless
* all_visible is also set to true.
*
* Also keep track of the visibility cutoff xid for recovery conflicts.
* The number of tuples removed from the page is returned in
* presult.ndeleted. It should not be confused with presult.lpdead_items;
* presult.lpdead_items's final value can be thought of as the number of
* tuples that were deleted from indexes.
*
* We will update the VM after collecting LP_DEAD items and freezing
* tuples. Pruning will have determined whether or not the page is
* all-visible.
*/
all_visible = true;
all_frozen = true;
visibility_cutoff_xid = InvalidTransactionId;
prune_options = HEAP_PAGE_PRUNE_FREEZE;
if (vacrel->nindexes == 0)
prune_options |= HEAP_PAGE_PRUNE_MARK_UNUSED_NOW;
/*
* Now scan the page to collect LP_DEAD items and update the variables set
* just above.
*/
for (offnum = FirstOffsetNumber;
offnum <= maxoff;
offnum = OffsetNumberNext(offnum))
{
HeapTupleHeader htup;
bool totally_frozen;
heap_page_prune_and_freeze(rel, buf, vacrel->vistest, prune_options,
&vacrel->cutoffs, &presult, PRUNE_VACUUM_SCAN,
&vacrel->offnum,
&vacrel->NewRelfrozenXid, &vacrel->NewRelminMxid);
/*
* Set the offset number so that we can display it along with any
* error that occurred while processing this tuple.
*/
vacrel->offnum = offnum;
itemid = PageGetItemId(page, offnum);
Assert(MultiXactIdIsValid(vacrel->NewRelminMxid));
Assert(TransactionIdIsValid(vacrel->NewRelfrozenXid));
if (!ItemIdIsUsed(itemid))
continue;
/* Redirect items mustn't be touched */
if (ItemIdIsRedirected(itemid))
{
/* page makes rel truncation unsafe */
hastup = true;
continue;
}
if (ItemIdIsDead(itemid))
{
/*
* Deliberately don't set hastup for LP_DEAD items. We make the
* soft assumption that any LP_DEAD items encountered here will
* become LP_UNUSED later on, before count_nondeletable_pages is
* reached. If we don't make this assumption then rel truncation
* will only happen every other VACUUM, at most. Besides, VACUUM
* must treat hastup/nonempty_pages as provisional no matter how
* LP_DEAD items are handled (handled here, or handled later on).
*
* Also deliberately delay unsetting all_visible until just before
* we return to lazy_scan_heap caller, as explained in full below.
* (This is another case where it's useful to anticipate that any
* LP_DEAD items will become LP_UNUSED during the ongoing VACUUM.)
*/
deadoffsets[lpdead_items++] = offnum;
continue;
}
Assert(ItemIdIsNormal(itemid));
htup = (HeapTupleHeader) PageGetItem(page, itemid);
/*
* The criteria for counting a tuple as live in this block need to
* match what analyze.c's acquire_sample_rows() does, otherwise VACUUM
* and ANALYZE may produce wildly different reltuples values, e.g.
* when there are many recently-dead tuples.
*
* The logic here is a bit simpler than acquire_sample_rows(), as
* VACUUM can't run inside a transaction block, which makes some cases
* impossible (e.g. in-progress insert from the same transaction).
*
* We treat LP_DEAD items (which are the closest thing to DEAD tuples
* that might be seen here) differently, too: we assume that they'll
* become LP_UNUSED before VACUUM finishes. This difference is only
* superficial. VACUUM effectively agrees with ANALYZE about DEAD
* items, in the end. VACUUM won't remember LP_DEAD items, but only
* because they're not supposed to be left behind when it is done.
* (Cases where we bypass index vacuuming will violate this optimistic
* assumption, but the overall impact of that should be negligible.)
*/
switch (htsv_get_valid_status(presult.htsv[offnum]))
{
case HEAPTUPLE_LIVE:
/*
* Count it as live. Not only is this natural, but it's also
* what acquire_sample_rows() does.
*/
live_tuples++;
/*
* Is the tuple definitely visible to all transactions?
*
* NB: Like with per-tuple hint bits, we can't set the
* PD_ALL_VISIBLE flag if the inserter committed
* asynchronously. See SetHintBits for more info. Check that
* the tuple is hinted xmin-committed because of that.
*/
if (all_visible)
{
TransactionId xmin;
if (!HeapTupleHeaderXminCommitted(htup))
{
all_visible = false;
break;
}
/*
* The inserter definitely committed. But is it old enough
* that everyone sees it as committed?
*/
xmin = HeapTupleHeaderGetXmin(htup);
if (!TransactionIdPrecedes(xmin,
vacrel->cutoffs.OldestXmin))
{
all_visible = false;
break;
}
/* Track newest xmin on page. */
if (TransactionIdFollows(xmin, visibility_cutoff_xid) &&
TransactionIdIsNormal(xmin))
visibility_cutoff_xid = xmin;
}
break;
case HEAPTUPLE_RECENTLY_DEAD:
/*
* If tuple is recently dead then we must not remove it from
* the relation. (We only remove items that are LP_DEAD from
* pruning.)
*/
recently_dead_tuples++;
all_visible = false;
break;
case HEAPTUPLE_INSERT_IN_PROGRESS:
/*
* We do not count these rows as live, because we expect the
* inserting transaction to update the counters at commit, and
* we assume that will happen only after we report our
* results. This assumption is a bit shaky, but it is what
* acquire_sample_rows() does, so be consistent.
*/
all_visible = false;
break;
case HEAPTUPLE_DELETE_IN_PROGRESS:
/* This is an expected case during concurrent vacuum */
all_visible = false;
/*
* Count such rows as live. As above, we assume the deleting
* transaction will commit and update the counters after we
* report.
*/
live_tuples++;
break;
default:
elog(ERROR, "unexpected HeapTupleSatisfiesVacuum result");
break;
}
hastup = true; /* page makes rel truncation unsafe */
/* Tuple with storage -- consider need to freeze */
if (heap_prepare_freeze_tuple(htup, &vacrel->cutoffs, &pagefrz,
&frozen[tuples_frozen], &totally_frozen))
{
/* Save prepared freeze plan for later */
frozen[tuples_frozen++].offset = offnum;
}
/*
* If any tuple isn't either totally frozen already or eligible to
* become totally frozen (according to its freeze plan), then the page
* definitely cannot be set all-frozen in the visibility map later on
*/
if (!totally_frozen)
all_frozen = false;
}
/*
* We have now divided every item on the page into either an LP_DEAD item
* that will need to be vacuumed in indexes later, or a LP_NORMAL tuple
* that remains and needs to be considered for freezing now (LP_UNUSED and
* LP_REDIRECT items also remain, but are of no further interest to us).
*/
vacrel->offnum = InvalidOffsetNumber;
/*
* Freeze the page when heap_prepare_freeze_tuple indicates that at least
* one XID/MXID from before FreezeLimit/MultiXactCutoff is present. Also
* freeze when pruning generated an FPI, if doing so means that we set the
* page all-frozen afterwards (might not happen until final heap pass).
*/
if (pagefrz.freeze_required || tuples_frozen == 0 ||
(all_visible && all_frozen &&
fpi_before != pgWalUsage.wal_fpi))
if (presult.nfrozen > 0)
{
/*
* We're freezing the page. Our final NewRelfrozenXid doesn't need to
* be affected by the XIDs that are just about to be frozen anyway.
* We don't increment the frozen_pages instrumentation counter when
* nfrozen == 0, since it only counts pages with newly frozen tuples
* (don't confuse that with pages newly set all-frozen in VM).
*/
vacrel->NewRelfrozenXid = pagefrz.FreezePageRelfrozenXid;
vacrel->NewRelminMxid = pagefrz.FreezePageRelminMxid;
if (tuples_frozen == 0)
{
/*
* We have no freeze plans to execute, so there's no added cost
* from following the freeze path. That's why it was chosen. This
* is important in the case where the page only contains totally
* frozen tuples at this point (perhaps only following pruning).
* Such pages can be marked all-frozen in the VM by our caller,
* even though none of its tuples were newly frozen here (note
* that the "no freeze" path never sets pages all-frozen).
*
* We never increment the frozen_pages instrumentation counter
* here, since it only counts pages with newly frozen tuples
* (don't confuse that with pages newly set all-frozen in VM).
*/
}
else
{
TransactionId snapshotConflictHorizon;
vacrel->frozen_pages++;
/*
* We can use visibility_cutoff_xid as our cutoff for conflicts
* when the whole page is eligible to become all-frozen in the VM
* once we're done with it. Otherwise we generate a conservative
* cutoff by stepping back from OldestXmin.
*/
if (all_visible && all_frozen)
{
/* Using same cutoff when setting VM is now unnecessary */
snapshotConflictHorizon = visibility_cutoff_xid;
visibility_cutoff_xid = InvalidTransactionId;
}
else
{
/* Avoids false conflicts when hot_standby_feedback in use */
snapshotConflictHorizon = vacrel->cutoffs.OldestXmin;
TransactionIdRetreat(snapshotConflictHorizon);
}
/* Execute all freeze plans for page as a single atomic action */
heap_freeze_execute_prepared(vacrel->rel, buf,
snapshotConflictHorizon,
frozen, tuples_frozen);
}
}
else
{
/*
* Page requires "no freeze" processing. It might be set all-visible
* in the visibility map, but it can never be set all-frozen.
*/
vacrel->NewRelfrozenXid = pagefrz.NoFreezePageRelfrozenXid;
vacrel->NewRelminMxid = pagefrz.NoFreezePageRelminMxid;
all_frozen = false;
tuples_frozen = 0; /* avoid miscounts in instrumentation */
vacrel->frozen_pages++;
}
/*
@ -1756,71 +1465,71 @@ lazy_scan_prune(LVRelState *vacrel,
*/
#ifdef USE_ASSERT_CHECKING
/* Note that all_frozen value does not matter when !all_visible */
if (all_visible && lpdead_items == 0)
if (presult.all_visible)
{
TransactionId debug_cutoff;
bool debug_all_frozen;
Assert(presult.lpdead_items == 0);
if (!heap_page_is_all_visible(vacrel, buf,
&debug_cutoff, &debug_all_frozen))
Assert(false);
Assert(presult.all_frozen == debug_all_frozen);
Assert(!TransactionIdIsValid(debug_cutoff) ||
debug_cutoff == visibility_cutoff_xid);
debug_cutoff == presult.vm_conflict_horizon);
}
#endif
/*
* Now save details of the LP_DEAD items from the page in vacrel
*/
if (lpdead_items > 0)
if (presult.lpdead_items > 0)
{
vacrel->lpdead_item_pages++;
dead_items_add(vacrel, blkno, deadoffsets, lpdead_items);
/*
* 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 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. It needs
* to reflect the present state of things, as expected by our caller.
* deadoffsets are collected incrementally in
* heap_page_prune_and_freeze() as each dead line pointer is recorded,
* with an indeterminate order, but dead_items_add requires them to be
* sorted.
*/
all_visible = false;
qsort(presult.deadoffsets, presult.lpdead_items, sizeof(OffsetNumber),
cmpOffsetNumbers);
dead_items_add(vacrel, blkno, presult.deadoffsets, presult.lpdead_items);
}
/* Finally, add page-local counts to whole-VACUUM counts */
vacrel->tuples_deleted += presult.ndeleted;
vacrel->tuples_frozen += tuples_frozen;
vacrel->lpdead_items += lpdead_items;
vacrel->live_tuples += live_tuples;
vacrel->recently_dead_tuples += recently_dead_tuples;
vacrel->tuples_frozen += presult.nfrozen;
vacrel->lpdead_items += presult.lpdead_items;
vacrel->live_tuples += presult.live_tuples;
vacrel->recently_dead_tuples += presult.recently_dead_tuples;
/* Can't truncate this page */
if (hastup)
if (presult.hastup)
vacrel->nonempty_pages = blkno + 1;
/* Did we find LP_DEAD items? */
*has_lpdead_items = (lpdead_items > 0);
*has_lpdead_items = (presult.lpdead_items > 0);
Assert(!all_visible || !(*has_lpdead_items));
Assert(!presult.all_visible || !(*has_lpdead_items));
/*
* Handle setting visibility map bit based on information from the VM (as
* of last heap_vac_scan_next_block() call), and from all_visible and
* all_frozen variables
*/
if (!all_visible_according_to_vm && all_visible)
if (!all_visible_according_to_vm && presult.all_visible)
{
uint8 flags = VISIBILITYMAP_ALL_VISIBLE;
if (all_frozen)
if (presult.all_frozen)
{
Assert(!TransactionIdIsValid(visibility_cutoff_xid));
Assert(!TransactionIdIsValid(presult.vm_conflict_horizon));
flags |= VISIBILITYMAP_ALL_FROZEN;
}
@ -1840,7 +1549,7 @@ lazy_scan_prune(LVRelState *vacrel,
PageSetAllVisible(page);
MarkBufferDirty(buf);
visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, visibility_cutoff_xid,
vmbuffer, presult.vm_conflict_horizon,
flags);
}
@ -1873,7 +1582,7 @@ lazy_scan_prune(LVRelState *vacrel,
* There should never be LP_DEAD items on a page with PD_ALL_VISIBLE set,
* however.
*/
else if (lpdead_items > 0 && PageIsAllVisible(page))
else if (presult.lpdead_items > 0 && PageIsAllVisible(page))
{
elog(WARNING, "page containing LP_DEAD items is marked as all-visible in relation \"%s\" page %u",
vacrel->relname, blkno);
@ -1888,8 +1597,8 @@ lazy_scan_prune(LVRelState *vacrel,
* 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.
*/
else if (all_visible_according_to_vm && all_visible &&
all_frozen && !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
else if (all_visible_according_to_vm && presult.all_visible &&
presult.all_frozen && !VM_ALL_FROZEN(vacrel->rel, blkno, &vmbuffer))
{
/*
* Avoid relying on all_visible_according_to_vm as a proxy for the
@ -1905,11 +1614,11 @@ lazy_scan_prune(LVRelState *vacrel,
/*
* Set the page all-frozen (and all-visible) in the VM.
*
* We can pass InvalidTransactionId as our visibility_cutoff_xid,
* since a snapshotConflictHorizon sufficient to make everything safe
* for REDO was logged when the page's tuples were frozen.
* We can pass InvalidTransactionId as our cutoff_xid, since a
* snapshotConflictHorizon sufficient to make everything safe for REDO
* was logged when the page's tuples were frozen.
*/
Assert(!TransactionIdIsValid(visibility_cutoff_xid));
Assert(!TransactionIdIsValid(presult.vm_conflict_horizon));
visibilitymap_set(vacrel->rel, blkno, buf, InvalidXLogRecPtr,
vmbuffer, InvalidTransactionId,
VISIBILITYMAP_ALL_VISIBLE |

6
src/backend/storage/ipc/procarray.c
View File

@ -1715,9 +1715,9 @@ TransactionIdIsActive(TransactionId xid)
* Note: the approximate horizons (see definition of GlobalVisState) are
* updated by the computations done here. That's currently required for
* correctness and a small optimization. Without doing so it's possible that
* heap vacuum's call to heap_page_prune() uses a more conservative horizon
* than later when deciding which tuples can be removed - which the code
* doesn't expect (breaking HOT).
* heap vacuum's call to heap_page_prune_and_freeze() uses a more conservative
* horizon than later when deciding which tuples can be removed - which the
* code doesn't expect (breaking HOT).
*/
static void
ComputeXidHorizons(ComputeXidHorizonsResult *h)

85
src/include/access/heapam.h
View File

@ -36,8 +36,9 @@
#define HEAP_INSERT_NO_LOGICAL TABLE_INSERT_NO_LOGICAL
#define HEAP_INSERT_SPECULATIVE 0x0010
/* "options" flag bits for heap_page_prune */
/* "options" flag bits for heap_page_prune_and_freeze */
#define HEAP_PAGE_PRUNE_MARK_UNUSED_NOW (1 << 0)
#define HEAP_PAGE_PRUNE_FREEZE (1 << 1)
typedef struct BulkInsertStateData *BulkInsertState;
struct TupleTableSlot;
@ -195,26 +196,49 @@ typedef struct HeapPageFreeze
} HeapPageFreeze;
/*
* Per-page state returned from pruning
* Per-page state returned by heap_page_prune_and_freeze()
*/
typedef struct PruneResult
typedef struct PruneFreezeResult
{
int ndeleted; /* Number of tuples deleted from the page */
int nnewlpdead; /* Number of newly LP_DEAD items */
int nfrozen; /* Number of tuples we froze */
/* Number of live and recently dead tuples on the page, after pruning */
int live_tuples;
int recently_dead_tuples;
/*
* Tuple visibility is only computed once for each tuple, for correctness
* and efficiency reasons; see comment in heap_page_prune() for details.
* This is of type int8[], instead of HTSV_Result[], so we can use -1 to
* indicate no visibility has been computed, e.g. for LP_DEAD items.
* all_visible and all_frozen indicate if the all-visible and all-frozen
* bits in the visibility map can be set for this page, after pruning.
*
* This needs to be MaxHeapTuplesPerPage + 1 long as FirstOffsetNumber is
* 1. Otherwise every access would need to subtract 1.
* vm_conflict_horizon is the newest xmin of live tuples on the page. The
* caller can use it as the conflict horizon when setting the VM bits. It
* is only valid if we froze some tuples (nfrozen > 0), and all_frozen is
* true.
*
* These are only set if the HEAP_PRUNE_FREEZE option is set.
*/
int8 htsv[MaxHeapTuplesPerPage + 1];
} PruneResult;
bool all_visible;
bool all_frozen;
TransactionId vm_conflict_horizon;
/* 'reason' codes for heap_page_prune() */
/*
* Whether or not the page makes rel truncation unsafe. This is set to
* 'true', even if the page contains LP_DEAD items. VACUUM will remove
* them before attempting to truncate.
*/
bool hastup;
/*
* LP_DEAD items on the page after pruning. Includes existing LP_DEAD
* items.
*/
int lpdead_items;
OffsetNumber deadoffsets[MaxHeapTuplesPerPage];
} PruneFreezeResult;
/* 'reason' codes for heap_page_prune_and_freeze() */
typedef enum
{
PRUNE_ON_ACCESS, /* on-access pruning */
@ -222,20 +246,6 @@ typedef enum
PRUNE_VACUUM_CLEANUP, /* VACUUM 2nd heap pass */
} PruneReason;
/*
* Pruning calculates tuple visibility once and saves the results in an array
* of int8. See PruneResult.htsv for details. This helper function is meant to
* guard against examining visibility status array members which have not yet
* been computed.
*/
static inline HTSV_Result
htsv_get_valid_status(int status)
{
Assert(status >= HEAPTUPLE_DEAD &&
status <= HEAPTUPLE_DELETE_IN_PROGRESS);
return (HTSV_Result) status;
}
/* ----------------
* function prototypes for heap access method
*
@ -309,9 +319,11 @@ extern bool heap_prepare_freeze_tuple(HeapTupleHeader tuple,
const struct VacuumCutoffs *cutoffs,
HeapPageFreeze *pagefrz,
HeapTupleFreeze *frz, bool *totally_frozen);
extern void heap_freeze_execute_prepared(Relation rel, Buffer buffer,
TransactionId snapshotConflictHorizon,
HeapTupleFreeze *tuples, int ntuples);
extern void heap_pre_freeze_checks(Buffer buffer,
HeapTupleFreeze *tuples, int ntuples);
extern void heap_freeze_prepared_tuples(Buffer buffer,
HeapTupleFreeze *tuples, int ntuples);
extern bool heap_freeze_tuple(HeapTupleHeader tuple,
TransactionId relfrozenxid, TransactionId relminmxid,
TransactionId FreezeLimit, TransactionId MultiXactCutoff);
@ -332,12 +344,15 @@ extern TransactionId heap_index_delete_tuples(Relation rel,
/* in heap/pruneheap.c */
struct GlobalVisState;
extern void heap_page_prune_opt(Relation relation, Buffer buffer);
extern void heap_page_prune(Relation relation, Buffer buffer,
struct GlobalVisState *vistest,
int options,
PruneResult *presult,
PruneReason reason,
OffsetNumber *off_loc);
extern void heap_page_prune_and_freeze(Relation relation, Buffer buffer,
struct GlobalVisState *vistest,
int options,
struct VacuumCutoffs *cutoffs,
PruneFreezeResult *presult,
PruneReason reason,
OffsetNumber *off_loc,
TransactionId *new_relfrozen_xid,
MultiXactId *new_relmin_mxid);
extern void heap_page_prune_execute(Buffer buffer, bool lp_truncate_only,
OffsetNumber *redirected, int nredirected,
OffsetNumber *nowdead, int ndead,

2
src/tools/pgindent/typedefs.list
View File

@ -2195,7 +2195,7 @@ PromptInterruptContext
ProtocolVersion
PrsStorage
PruneReason
PruneResult
PruneFreezeResult
PruneState
PruneStepResult
PsqlScanCallbacks