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Commit8aa02b5

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Add ExecStorePinnedBufferHeapTuple.
This allows to avoid an unnecessary pin/unpin cycle when storing atuple in an already pinned buffer into a slot, when the pin isn'tfurther needed at the call site.Only a single caller for now (to ensure coverage), but upcomingpatches will increase use of the new function.Author: Andres FreundDiscussion:https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
1 parentf4b6341 commit8aa02b5

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3 files changed

+60
-19
lines changed

3 files changed

+60
-19
lines changed

‎src/backend/executor/execTuples.c

Lines changed: 52 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -74,7 +74,11 @@ static TupleDesc ExecTypeFromTLInternal(List *targetList,
7474
staticpg_attribute_always_inlinevoid
7575
slot_deform_heap_tuple(TupleTableSlot*slot,HeapTupletuple,uint32*offp,
7676
intnatts);
77-
staticvoidtts_buffer_heap_store_tuple(TupleTableSlot*slot,HeapTupletuple,Bufferbuffer);
77+
staticinlinevoidtts_buffer_heap_store_tuple(TupleTableSlot*slot,
78+
HeapTupletuple,
79+
Bufferbuffer,
80+
booltransfer_pin);
81+
staticvoidtts_heap_store_tuple(TupleTableSlot*slot,HeapTupletuple,boolshouldFree);
7882

7983

8084
constTupleTableSlotOpsTTSOpsVirtual;
@@ -743,7 +747,9 @@ tts_buffer_heap_copyslot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
743747
}
744748
else
745749
{
746-
tts_buffer_heap_store_tuple(dstslot,bsrcslot->base.tuple,bsrcslot->buffer);
750+
tts_buffer_heap_store_tuple(dstslot,bsrcslot->base.tuple,
751+
bsrcslot->buffer, false);
752+
747753
/*
748754
* Need to materialize because the HeapTupleData portion of the tuple
749755
* might be in a foreign memory context. That's annoying, but until
@@ -792,8 +798,9 @@ tts_buffer_heap_copy_minimal_tuple(TupleTableSlot *slot)
792798
returnminimal_tuple_from_heap_tuple(bslot->base.tuple);
793799
}
794800

795-
staticvoid
796-
tts_buffer_heap_store_tuple(TupleTableSlot*slot,HeapTupletuple,Bufferbuffer)
801+
staticinlinevoid
802+
tts_buffer_heap_store_tuple(TupleTableSlot*slot,HeapTupletuple,
803+
Bufferbuffer,booltransfer_pin)
797804
{
798805
BufferHeapTupleTableSlot*bslot= (BufferHeapTupleTableSlot*)slot;
799806

@@ -813,7 +820,9 @@ tts_buffer_heap_store_tuple(TupleTableSlot *slot, HeapTuple tuple, Buffer buffer
813820

814821
/*
815822
* If tuple is on a disk page, keep the page pinned as long as we hold a
816-
* pointer into it. We assume the caller already has such a pin.
823+
* pointer into it. We assume the caller already has such a pin. If
824+
* transfer_pin is true, we'll transfer that pin to this slot, if not
825+
* we'll pin it again ourselves.
817826
*
818827
* This is coded to optimize the case where the slot previously held a
819828
* tuple on the same disk page: in that case releasing and re-acquiring
@@ -824,8 +833,19 @@ tts_buffer_heap_store_tuple(TupleTableSlot *slot, HeapTuple tuple, Buffer buffer
824833
{
825834
if (BufferIsValid(bslot->buffer))
826835
ReleaseBuffer(bslot->buffer);
836+
827837
bslot->buffer=buffer;
828-
IncrBufferRefCount(buffer);
838+
839+
if (!transfer_pin&&BufferIsValid(buffer))
840+
IncrBufferRefCount(buffer);
841+
}
842+
elseif (transfer_pin&&BufferIsValid(buffer))
843+
{
844+
/*
845+
* In transfer_pin mode the caller won't know about the same-page
846+
* optimization, so we gotta release its pin.
847+
*/
848+
ReleaseBuffer(buffer);
829849
}
830850
}
831851

@@ -1321,7 +1341,32 @@ ExecStoreBufferHeapTuple(HeapTuple tuple,
13211341

13221342
if (unlikely(!TTS_IS_BUFFERTUPLE(slot)))
13231343
elog(ERROR,"trying to store an on-disk heap tuple into wrong type of slot");
1324-
tts_buffer_heap_store_tuple(slot,tuple,buffer);
1344+
tts_buffer_heap_store_tuple(slot,tuple,buffer, false);
1345+
1346+
1347+
returnslot;
1348+
}
1349+
1350+
/*
1351+
* Like ExecStoreBufferHeapTuple, but transfer an existing pin from the caller
1352+
* to the slot, i.e. the caller doesn't need to, and may not, release the pin.
1353+
*/
1354+
TupleTableSlot*
1355+
ExecStorePinnedBufferHeapTuple(HeapTupletuple,
1356+
TupleTableSlot*slot,
1357+
Bufferbuffer)
1358+
{
1359+
/*
1360+
* sanity checks
1361+
*/
1362+
Assert(tuple!=NULL);
1363+
Assert(slot!=NULL);
1364+
Assert(slot->tts_tupleDescriptor!=NULL);
1365+
Assert(BufferIsValid(buffer));
1366+
1367+
if (unlikely(!TTS_IS_BUFFERTUPLE(slot)))
1368+
elog(ERROR,"trying to store an on-disk heap tuple into wrong type of slot");
1369+
tts_buffer_heap_store_tuple(slot,tuple,buffer, true);
13251370

13261371
returnslot;
13271372
}

‎src/backend/executor/nodeTidscan.c

Lines changed: 5 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -379,19 +379,12 @@ TidNext(TidScanState *node)
379379
{
380380
/*
381381
* Store the scanned tuple in the scan tuple slot of the scan
382-
* state. Eventually we will only do this and not return a tuple.
382+
* state, transferring the pin to the slot.
383383
*/
384-
ExecStoreBufferHeapTuple(tuple,/* tuple to store */
385-
slot,/* slot to store in */
386-
buffer);/* buffer associated with
387-
* tuple */
388-
389-
/*
390-
* At this point we have an extra pin on the buffer, because
391-
* ExecStoreHeapTuple incremented the pin count. Drop our local
392-
* pin.
393-
*/
394-
ReleaseBuffer(buffer);
384+
ExecStorePinnedBufferHeapTuple(tuple,/* tuple to store */
385+
slot,/* slot to store in */
386+
buffer);/* buffer associated with
387+
* tuple */
395388

396389
returnslot;
397390
}

‎src/include/executor/tuptable.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -305,6 +305,9 @@ extern void ExecForceStoreHeapTuple(HeapTuple tuple, TupleTableSlot *slot);
305305
externTupleTableSlot*ExecStoreBufferHeapTuple(HeapTupletuple,
306306
TupleTableSlot*slot,
307307
Bufferbuffer);
308+
externTupleTableSlot*ExecStorePinnedBufferHeapTuple(HeapTupletuple,
309+
TupleTableSlot*slot,
310+
Bufferbuffer);
308311
externTupleTableSlot*ExecStoreMinimalTuple(MinimalTuplemtup,
309312
TupleTableSlot*slot,
310313
boolshouldFree);

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