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Don't force materializing when copying a buffer tuple table slot.

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After 5408e233f0 it's not necessary to force materializing the
target slot when copying from one buffer slot to another. Previously
that was required because the HeapTupleData portion of the source slot
wasn't guaranteed to stay valid long enough, but now we can simply
copy that part into the destination slot's tupdata.

Author: Andres Freund
This commit is contained in:
Andres Freund
2019-02-28 13:55:27 -08:00
parent 2c31825fb9
commit 8f0577386e
1 changed files with 11 additions and 8 deletions
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19
src/backend/executor/execTuples.c
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@ -747,10 +747,12 @@ tts_buffer_heap_copyslot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
/* /*
* If the source slot is of a different kind, or is a buffer slot that has * If the source slot is of a different kind, or is a buffer slot that has
* been materialized, make a new copy of the tuple. * been materialized / is virtual, make a new copy of the tuple. Otherwise
* make a new reference to the in-buffer tuple.
*/ */
if (dstslot->tts_ops != srcslot->tts_ops || if (dstslot->tts_ops != srcslot->tts_ops ||
TTS_SHOULDFREE(srcslot)) TTS_SHOULDFREE(srcslot) ||
!bsrcslot->base.tuple)
{ {
MemoryContext oldContext; MemoryContext oldContext;
@ -763,18 +765,19 @@ tts_buffer_heap_copyslot(TupleTableSlot *dstslot, TupleTableSlot *srcslot)
} }
else else
{ {
if (!bsrcslot->base.tuple) Assert(BufferIsValid(bsrcslot->buffer));
tts_buffer_heap_materialize(srcslot);
tts_buffer_heap_store_tuple(dstslot, bsrcslot->base.tuple, tts_buffer_heap_store_tuple(dstslot, bsrcslot->base.tuple,
bsrcslot->buffer, false); bsrcslot->buffer, false);
/* /*
* Need to materialize because the HeapTupleData portion of the tuple * The HeapTupleData portion of the source tuple might be shorter
* might be in a foreign memory context. That's annoying, but until * lived than the destination slot. Therefore copy the HeapTuple into
* that's moved into the slot, unavoidable. * our slot's tupdata, which is guaranteed to live long enough (but
* will still point into the buffer).
*/ */
tts_buffer_heap_materialize(dstslot); memcpy(&bdstslot->base.tupdata, bdstslot->base.tuple, sizeof(HeapTupleData));
bdstslot->base.tuple = &bdstslot->base.tupdata;
} }
} }