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Commit370bc77

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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 parenta0c8d60 commit370bc77

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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
@@ -6023,8 +6023,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
60236023
* transaction. If compatible, return true with the buffer exclusive-locked,
60246024
* and the caller must release that by calling
60256025
* heap_inplace_update_and_unlock(), calling heap_inplace_unlock(), or raising
6026-
* an error. Otherwise,return false after blocking transactions, if any,
6027-
*have ended.
6026+
* an error. Otherwise,call release_callback(arg), wait for blocking
6027+
*transactions to end, and return false.
60286028
*
60296029
* Since this is intended for system catalogs and SERIALIZABLE doesn't cover
60306030
* DDL, this doesn't guarantee any particular predicate locking.
@@ -6058,7 +6058,8 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
60586058
*/
60596059
bool
60606060
heap_inplace_lock(Relationrelation,
6061-
HeapTupleoldtup_ptr,Bufferbuffer)
6061+
HeapTupleoldtup_ptr,Bufferbuffer,
6062+
void (*release_callback) (void*),void*arg)
60626063
{
60636064
HeapTupleDataoldtup=*oldtup_ptr;/* minimize diff vs. heap_update() */
60646065
TM_Resultresult;
@@ -6123,6 +6124,7 @@ heap_inplace_lock(Relation relation,
61236124
lockmode,NULL))
61246125
{
61256126
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6127+
release_callback(arg);
61266128
ret= false;
61276129
MultiXactIdWait((MultiXactId)xwait,mxact_status,infomask,
61286130
relation,&oldtup.t_self,XLTW_Update,
@@ -6138,6 +6140,7 @@ heap_inplace_lock(Relation relation,
61386140
else
61396141
{
61406142
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6143+
release_callback(arg);
61416144
ret= false;
61426145
XactLockTableWait(xwait,relation,&oldtup.t_self,
61436146
XLTW_Update);
@@ -6149,6 +6152,7 @@ heap_inplace_lock(Relation relation,
61496152
if (!ret)
61506153
{
61516154
LockBuffer(buffer,BUFFER_LOCK_UNLOCK);
6155+
release_callback(arg);
61526156
}
61536157
}
61546158

‎src/backend/access/index/genam.c‎

Lines changed: 5 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -805,6 +805,7 @@ systable_inplace_update_begin(Relation relation,
805805
intretries=0;
806806
SysScanDescscan;
807807
HeapTupleoldtup;
808+
BufferHeapTupleTableSlot*bslot;
808809

809810
/*
810811
* For now, we don't allow parallel updates. Unlike a regular update,
@@ -826,10 +827,9 @@ systable_inplace_update_begin(Relation relation,
826827
Assert(IsInplaceUpdateRelation(relation)|| !IsSystemRelation(relation));
827828

828829
/* Loop for an exclusive-locked buffer of a non-updated tuple. */
829-
for (;;)
830+
do
830831
{
831832
TupleTableSlot*slot;
832-
BufferHeapTupleTableSlot*bslot;
833833

834834
CHECK_FOR_INTERRUPTS();
835835

@@ -855,11 +855,9 @@ systable_inplace_update_begin(Relation relation,
855855
slot=scan->slot;
856856
Assert(TTS_IS_BUFFERTUPLE(slot));
857857
bslot= (BufferHeapTupleTableSlot*)slot;
858-
if (heap_inplace_lock(scan->heap_rel,
859-
bslot->base.tuple,bslot->buffer))
860-
break;
861-
systable_endscan(scan);
862-
};
858+
}while (!heap_inplace_lock(scan->heap_rel,
859+
bslot->base.tuple,bslot->buffer,
860+
(void (*) (void*))systable_endscan,scan));
863861

864862
*oldtupcopy=heap_copytuple(oldtup);
865863
*state=scan;

‎src/include/access/heapam.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -257,7 +257,8 @@ extern TM_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
257257
Buffer*buffer,structTM_FailureData*tmfd);
258258

259259
externboolheap_inplace_lock(Relationrelation,
260-
HeapTupleoldtup_ptr,Bufferbuffer);
260+
HeapTupleoldtup_ptr,Bufferbuffer,
261+
void (*release_callback) (void*),void*arg);
261262
externvoidheap_inplace_update_and_unlock(Relationrelation,
262263
HeapTupleoldtup,HeapTupletuple,
263264
Bufferbuffer);

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