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Commit30d47ec

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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 parent502e7bf commit30d47ec

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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
@@ -6165,8 +6165,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
61656165
* transaction. If compatible, return true with the buffer exclusive-locked,
61666166
* and the caller must release that by calling
61676167
* heap_inplace_update_and_unlock(), calling heap_inplace_unlock(), or raising
6168-
* an error. Otherwise,return false after blocking transactions, if any,
6169-
*have ended.
6168+
* an error. Otherwise,call release_callback(arg), wait for blocking
6169+
*transactions to end, and return false.
61706170
*
61716171
* Since this is intended for system catalogs and SERIALIZABLE doesn't cover
61726172
* DDL, this doesn't guarantee any particular predicate locking.
@@ -6200,7 +6200,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
62006200
*/
62016201
bool
62026202
heap_inplace_lock(Relationrelation,
6203-
HeapTupleoldtup_ptr,Bufferbuffer)
6203+
HeapTupleoldtup_ptr,Bufferbuffer,
6204+
void (*release_callback) (void*),void*arg)
62046205
{
62056206
HeapTupleDataoldtup=*oldtup_ptr;/* minimize diff vs. heap_update() */
62066207
TM_Resultresult;
@@ -6265,6 +6266,7 @@ heap_inplace_lock(Relation relation,
62656266
lockmode,NULL))
62666267
{
62676268
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6269+
release_callback(arg);
62686270
ret= false;
62696271
MultiXactIdWait((MultiXactId)xwait,mxact_status,infomask,
62706272
relation,&oldtup.t_self,XLTW_Update,
@@ -6280,6 +6282,7 @@ heap_inplace_lock(Relation relation,
62806282
else
62816283
{
62826284
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6285+
release_callback(arg);
62836286
ret= false;
62846287
XactLockTableWait(xwait,relation,&oldtup.t_self,
62856288
XLTW_Update);
@@ -6291,6 +6294,7 @@ heap_inplace_lock(Relation relation,
62916294
if (!ret)
62926295
{
62936296
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6297+
release_callback(arg);
62946298
}
62956299
}
62966300

‎src/backend/access/index/genam.c

Lines changed: 5 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -814,6 +814,7 @@ systable_inplace_update_begin(Relation relation,
814814
intretries=0;
815815
SysScanDescscan;
816816
HeapTupleoldtup;
817+
BufferHeapTupleTableSlot*bslot;
817818

818819
/*
819820
* For now, we don't allow parallel updates. Unlike a regular update,
@@ -835,10 +836,9 @@ systable_inplace_update_begin(Relation relation,
835836
Assert(IsInplaceUpdateRelation(relation)|| !IsSystemRelation(relation));
836837

837838
/* Loop for an exclusive-locked buffer of a non-updated tuple. */
838-
for (;;)
839+
do
839840
{
840841
TupleTableSlot*slot;
841-
BufferHeapTupleTableSlot*bslot;
842842

843843
CHECK_FOR_INTERRUPTS();
844844

@@ -864,11 +864,9 @@ systable_inplace_update_begin(Relation relation,
864864
slot=scan->slot;
865865
Assert(TTS_IS_BUFFERTUPLE(slot));
866866
bslot= (BufferHeapTupleTableSlot*)slot;
867-
if (heap_inplace_lock(scan->heap_rel,
868-
bslot->base.tuple,bslot->buffer))
869-
break;
870-
systable_endscan(scan);
871-
};
867+
}while (!heap_inplace_lock(scan->heap_rel,
868+
bslot->base.tuple,bslot->buffer,
869+
(void (*) (void*))systable_endscan,scan));
872870

873871
*oldtupcopy=heap_copytuple(oldtup);
874872
*state=scan;

‎src/include/access/heapam.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -338,7 +338,8 @@ extern TM_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
338338
Buffer*buffer,structTM_FailureData*tmfd);
339339

340340
externboolheap_inplace_lock(Relationrelation,
341-
HeapTupleoldtup_ptr,Bufferbuffer);
341+
HeapTupleoldtup_ptr,Bufferbuffer,
342+
void (*release_callback) (void*),void*arg);
342343
externvoidheap_inplace_update_and_unlock(Relationrelation,
343344
HeapTupleoldtup,HeapTupletuple,
344345
Bufferbuffer);

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