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Commit2a912bc

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committed
Unpin buffer before inplace update waits for an XID to end.
Commita07e03f changed inplace updatesto wait for heap_update() commands like GRANT TABLE and GRANT DATABASE.By keeping the pin during that wait, a sequence of autovacuum workersand an uncommitted GRANT starved one foreground LockBufferForCleanup()for six minutes, on buildfarm member sarus. Prevent, at the cost of abit of complexity. Back-patch to v12, like the earlier commit. Thatcommit and heap_inplace_lock() have not yet appeared in any release.Discussion:https://postgr.es/m/20241026184936.ae.nmisch@google.com
1 parent8a84861 commit2a912bc

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3 files changed

+14
-11
lines changed

3 files changed

+14
-11
lines changed

‎src/backend/access/heap/heapam.c

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -5943,8 +5943,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
59435943
* transaction. If compatible, return true with the buffer exclusive-locked,
59445944
* and the caller must release that by calling
59455945
* heap_inplace_update_and_unlock(), calling heap_inplace_unlock(), or raising
5946-
* an error. Otherwise,return false after blocking transactions, if any,
5947-
*have ended.
5946+
* an error. Otherwise,call release_callback(arg), wait for blocking
5947+
*transactions to end, and return false.
59485948
*
59495949
* Since this is intended for system catalogs and SERIALIZABLE doesn't cover
59505950
* DDL, this doesn't guarantee any particular predicate locking.
@@ -5978,7 +5978,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
59785978
*/
59795979
bool
59805980
heap_inplace_lock(Relationrelation,
5981-
HeapTupleoldtup_ptr,Bufferbuffer)
5981+
HeapTupleoldtup_ptr,Bufferbuffer,
5982+
void (*release_callback) (void*),void*arg)
59825983
{
59835984
HeapTupleDataoldtup=*oldtup_ptr;/* minimize diff vs. heap_update() */
59845985
TM_Resultresult;
@@ -6043,6 +6044,7 @@ heap_inplace_lock(Relation relation,
60436044
lockmode,NULL))
60446045
{
60456046
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6047+
release_callback(arg);
60466048
ret= false;
60476049
MultiXactIdWait((MultiXactId)xwait,mxact_status,infomask,
60486050
relation,&oldtup.t_self,XLTW_Update,
@@ -6058,6 +6060,7 @@ heap_inplace_lock(Relation relation,
60586060
else
60596061
{
60606062
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6063+
release_callback(arg);
60616064
ret= false;
60626065
XactLockTableWait(xwait,relation,&oldtup.t_self,
60636066
XLTW_Update);
@@ -6069,6 +6072,7 @@ heap_inplace_lock(Relation relation,
60696072
if (!ret)
60706073
{
60716074
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6075+
release_callback(arg);
60726076
}
60736077
}
60746078

‎src/backend/access/index/genam.c

Lines changed: 5 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -708,6 +708,7 @@ systable_inplace_update_begin(Relation relation,
708708
intretries=0;
709709
SysScanDescscan;
710710
HeapTupleoldtup;
711+
BufferHeapTupleTableSlot*bslot;
711712

712713
/*
713714
* For now, we don't allow parallel updates. Unlike a regular update,
@@ -729,10 +730,9 @@ systable_inplace_update_begin(Relation relation,
729730
Assert(IsInplaceUpdateRelation(relation)|| !IsSystemRelation(relation));
730731

731732
/* Loop for an exclusive-locked buffer of a non-updated tuple. */
732-
for (;;)
733+
do
733734
{
734735
TupleTableSlot*slot;
735-
BufferHeapTupleTableSlot*bslot;
736736

737737
CHECK_FOR_INTERRUPTS();
738738

@@ -758,11 +758,9 @@ systable_inplace_update_begin(Relation relation,
758758
slot=scan->slot;
759759
Assert(TTS_IS_BUFFERTUPLE(slot));
760760
bslot= (BufferHeapTupleTableSlot*)slot;
761-
if (heap_inplace_lock(scan->heap_rel,
762-
bslot->base.tuple,bslot->buffer))
763-
break;
764-
systable_endscan(scan);
765-
};
761+
}while (!heap_inplace_lock(scan->heap_rel,
762+
bslot->base.tuple,bslot->buffer,
763+
(void (*) (void*))systable_endscan,scan));
766764

767765
*oldtupcopy=heap_copytuple(oldtup);
768766
*state=scan;

‎src/include/access/heapam.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -158,7 +158,8 @@ extern TM_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
158158
Buffer*buffer,structTM_FailureData*tmfd);
159159

160160
externboolheap_inplace_lock(Relationrelation,
161-
HeapTupleoldtup_ptr,Bufferbuffer);
161+
HeapTupleoldtup_ptr,Bufferbuffer,
162+
void (*release_callback) (void*),void*arg);
162163
externvoidheap_inplace_update_and_unlock(Relationrelation,
163164
HeapTupleoldtup,HeapTupletuple,
164165
Bufferbuffer);

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