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Store tuples for EvalPlanQual in slots, rather than as HeapTuples.

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For the upcoming pluggable table access methods it's quite
inconvenient to store tuples as HeapTuples, as that'd require
converting tuples from a their native format into HeapTuples. Instead
use slots to manage epq tuples.

To fit into that scheme, change the foreign data wrapper callback
RefetchForeignRow, to store the tuple in a slot. Insist on using the
caller provided slot, so it conveniently can be stored in the
corresponding EPQ slot.  As there is no in core user of
RefetchForeignRow, that change was done blindly, but we plan to test
that soon.

To avoid duplicating that work for row locks, move row locks to just
directly use the EPQ slots - it previously temporarily stored tuples
in LockRowsState.lr_curtuples, but that doesn't seem beneficial, given
we'd possibly end up with a significant number of additional slots.

The behaviour of es_epqTupleSet[rti -1] is now checked by
es_epqTupleSlot[rti -1] != NULL, as that is distinguishable from a
slot containing an empty tuple.

Author: Andres Freund, Haribabu Kommi, Ashutosh Bapat
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
This commit is contained in:
Andres Freund
2019-03-01 10:37:57 -08:00
parent 6cbdbd9e8d
commit ad0bda5d24
13 changed files with 189 additions and 213 deletions
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16
src/backend/executor/execScan.c
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@ -40,7 +40,7 @@ ExecScanFetch(ScanState *node,
CHECK_FOR_INTERRUPTS();
if (estate->es_epqTuple != NULL)
if (estate->es_epqTupleSlot != NULL)
{
/*
* We are inside an EvalPlanQual recheck. Return the test tuple if
@ -63,7 +63,7 @@ ExecScanFetch(ScanState *node,
ExecClearTuple(slot); /* would not be returned by scan */
return slot;
}
else if (estate->es_epqTupleSet[scanrelid - 1])
else if (estate->es_epqTupleSlot[scanrelid - 1] != NULL)
{
TupleTableSlot *slot = node->ss_ScanTupleSlot;
@ -73,17 +73,15 @@ ExecScanFetch(ScanState *node,
/* Else mark to remember that we shouldn't return more */
estate->es_epqScanDone[scanrelid - 1] = true;
/* Return empty slot if we haven't got a test tuple */
if (estate->es_epqTuple[scanrelid - 1] == NULL)
return ExecClearTuple(slot);
slot = estate->es_epqTupleSlot[scanrelid - 1];
/* Store test tuple in the plan node's scan slot */
ExecForceStoreHeapTuple(estate->es_epqTuple[scanrelid - 1],
slot);
/* Return empty slot if we haven't got a test tuple */
if (TupIsNull(slot))
return NULL;
/* Check if it meets the access-method conditions */
if (!(*recheckMtd) (node, slot))
ExecClearTuple(slot); /* would not be returned by scan */
return ExecClearTuple(slot); /* would not be returned by scan */
return slot;
}