Do execGrouping.c via expression eval machinery, take two.

This has a performance benefit on own, although not hugely so. The
primary benefit is that it will allow for to JIT tuple deforming and
comparator invocations.

Large parts of this were previously committed (773aec7aa), but the
commit contained an omission around cross-type comparisons and was
thus reverted.

Author: Andres Freund
Discussion: https://postgr.es/m/20171129080934.amqqkke2zjtekd4t@alap3.anarazel.de

src/backend/executor/execExpr.c

@@ -3193,3 +3193,146 @@ ExecBuildAggTransCall(ExprState *state, AggState *aggstate,
 		as->d.agg_strict_trans_check.jumpnull = state->steps_len;
 	}
 }
+
+/*
+ * Build equality expression that can be evaluated using ExecQual(), returning
+ * true if the expression context's inner/outer tuple are NOT DISTINCT. I.e
+ * two nulls match, a null and a not-null don't match.
+ *
+ * desc: tuple descriptor of the to-be-compared tuples
+ * numCols: the number of attributes to be examined
+ * keyColIdx: array of attribute column numbers
+ * eqFunctions: array of function oids of the equality functions to use
+ * parent: parent executor node
+ */
+ExprState *
+ExecBuildGroupingEqual(TupleDesc ldesc, TupleDesc rdesc,
+					   int numCols,
+					   AttrNumber *keyColIdx,
+					   Oid *eqfunctions,
+					   PlanState *parent)
+{
+	ExprState  *state = makeNode(ExprState);
+	ExprEvalStep scratch = {0};
+	int			natt;
+	int			maxatt = -1;
+	List	   *adjust_jumps = NIL;
+	ListCell   *lc;
+
+	/*
+	 * When no columns are actually compared, the result's always true. See
+	 * special case in ExecQual().
+	 */
+	if (numCols == 0)
+		return NULL;
+
+	state->expr = NULL;
+	state->flags = EEO_FLAG_IS_QUAL;
+	state->parent = parent;
+
+	scratch.resvalue = &state->resvalue;
+	scratch.resnull = &state->resnull;
+
+	/* compute max needed attribute */
+	for (natt = 0; natt < numCols; natt++)
+	{
+		int			attno = keyColIdx[natt];
+
+		if (attno > maxatt)
+			maxatt = attno;
+	}
+	Assert(maxatt >= 0);
+
+	/* push deform steps */
+	scratch.opcode = EEOP_INNER_FETCHSOME;
+	scratch.d.fetch.last_var = maxatt;
+	ExprEvalPushStep(state, &scratch);
+
+	scratch.opcode = EEOP_OUTER_FETCHSOME;
+	scratch.d.fetch.last_var = maxatt;
+	ExprEvalPushStep(state, &scratch);
+
+	/*
+	 * Start comparing at the last field (least significant sort key). That's
+	 * the most likely to be different if we are dealing with sorted input.
+	 */
+	for (natt = numCols; --natt >= 0;)
+	{
+		int			attno = keyColIdx[natt];
+		Form_pg_attribute latt = TupleDescAttr(ldesc, attno - 1);
+		Form_pg_attribute ratt = TupleDescAttr(rdesc, attno - 1);
+		Oid			foid = eqfunctions[natt];
+		FmgrInfo   *finfo;
+		FunctionCallInfo fcinfo;
+		AclResult	aclresult;
+
+		/* Check permission to call function */
+		aclresult = pg_proc_aclcheck(foid, GetUserId(), ACL_EXECUTE);
+		if (aclresult != ACLCHECK_OK)
+			aclcheck_error(aclresult, OBJECT_FUNCTION, get_func_name(foid));
+
+		InvokeFunctionExecuteHook(foid);
+
+		/* Set up the primary fmgr lookup information */
+		finfo = palloc0(sizeof(FmgrInfo));
+		fcinfo = palloc0(sizeof(FunctionCallInfoData));
+		fmgr_info(foid, finfo);
+		fmgr_info_set_expr(NULL, finfo);
+		InitFunctionCallInfoData(*fcinfo, finfo, 2,
+								 InvalidOid, NULL, NULL);
+
+		/* left arg */
+		scratch.opcode = EEOP_INNER_VAR;
+		scratch.d.var.attnum = attno - 1;
+		scratch.d.var.vartype = latt->atttypid;
+		scratch.resvalue = &fcinfo->arg[0];
+		scratch.resnull = &fcinfo->argnull[0];
+		ExprEvalPushStep(state, &scratch);
+
+		/* right arg */
+		scratch.opcode = EEOP_OUTER_VAR;
+		scratch.d.var.attnum = attno - 1;
+		scratch.d.var.vartype = ratt->atttypid;
+		scratch.resvalue = &fcinfo->arg[1];
+		scratch.resnull = &fcinfo->argnull[1];
+		ExprEvalPushStep(state, &scratch);
+
+		/* evaluate distinctness */
+		scratch.opcode = EEOP_NOT_DISTINCT;
+		scratch.d.func.finfo = finfo;
+		scratch.d.func.fcinfo_data = fcinfo;
+		scratch.d.func.fn_addr = finfo->fn_addr;
+		scratch.d.func.nargs = 2;
+		scratch.resvalue = &state->resvalue;
+		scratch.resnull = &state->resnull;
+		ExprEvalPushStep(state, &scratch);
+
+		/* then emit EEOP_QUAL to detect if result is false (or null) */
+		scratch.opcode = EEOP_QUAL;
+		scratch.d.qualexpr.jumpdone = -1;
+		scratch.resvalue = &state->resvalue;
+		scratch.resnull = &state->resnull;
+		ExprEvalPushStep(state, &scratch);
+		adjust_jumps = lappend_int(adjust_jumps,
+								   state->steps_len - 1);
+	}
+
+	/* adjust jump targets */
+	foreach(lc, adjust_jumps)
+	{
+		ExprEvalStep *as = &state->steps[lfirst_int(lc)];
+
+		Assert(as->opcode == EEOP_QUAL);
+		Assert(as->d.qualexpr.jumpdone == -1);
+		as->d.qualexpr.jumpdone = state->steps_len;
+	}
+
+	scratch.resvalue = NULL;
+	scratch.resnull = NULL;
+	scratch.opcode = EEOP_DONE;
+	ExprEvalPushStep(state, &scratch);
+
+	ExecReadyExpr(state);
+
+	return state;
+}

src/backend/executor/execExprInterp.c

@@ -355,6 +355,7 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 		&&CASE_EEOP_MAKE_READONLY,
 		&&CASE_EEOP_IOCOERCE,
 		&&CASE_EEOP_DISTINCT,
+		&&CASE_EEOP_NOT_DISTINCT,
 		&&CASE_EEOP_NULLIF,
 		&&CASE_EEOP_SQLVALUEFUNCTION,
 		&&CASE_EEOP_CURRENTOFEXPR,
@@ -1198,6 +1199,34 @@ ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
 			EEO_NEXT();
 		}
 
+		/* see EEOP_DISTINCT for comments, this is just inverted */
+		EEO_CASE(EEOP_NOT_DISTINCT)
+		{
+			FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
+
+			if (fcinfo->argnull[0] && fcinfo->argnull[1])
+			{
+				*op->resvalue = BoolGetDatum(true);
+				*op->resnull = false;
+			}
+			else if (fcinfo->argnull[0] || fcinfo->argnull[1])
+			{
+				*op->resvalue = BoolGetDatum(false);
+				*op->resnull = false;
+			}
+			else
+			{
+				Datum		eqresult;
+
+				fcinfo->isnull = false;
+				eqresult = op->d.func.fn_addr(fcinfo);
+				*op->resvalue = eqresult;
+				*op->resnull = fcinfo->isnull;
+			}
+
+			EEO_NEXT();
+		}
+
 		EEO_CASE(EEOP_NULLIF)
 		{
 			/*

src/backend/executor/execGrouping.c

@@ -52,172 +52,33 @@ static int	TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tup
  *****************************************************************************/
 
 /*
- * execTuplesMatch
- *		Return true if two tuples match in all the indicated fields.
- *
- * This actually implements SQL's notion of "not distinct".  Two nulls
- * match, a null and a not-null don't match.
- *
- * slot1, slot2: the tuples to compare (must have same columns!)
- * numCols: the number of attributes to be examined
- * matchColIdx: array of attribute column numbers
- * eqFunctions: array of fmgr lookup info for the equality functions to use
- * evalContext: short-term memory context for executing the functions
- *
- * NB: evalContext is reset each time!
- */
-bool
-execTuplesMatch(TupleTableSlot *slot1,
-				TupleTableSlot *slot2,
-				int numCols,
-				AttrNumber *matchColIdx,
-				FmgrInfo *eqfunctions,
-				MemoryContext evalContext)
-{
-	MemoryContext oldContext;
-	bool		result;
-	int			i;
-
-	/* Reset and switch into the temp context. */
-	MemoryContextReset(evalContext);
-	oldContext = MemoryContextSwitchTo(evalContext);
-
-	/*
-	 * We cannot report a match without checking all the fields, but we can
-	 * report a non-match as soon as we find unequal fields.  So, start
-	 * comparing at the last field (least significant sort key). That's the
-	 * most likely to be different if we are dealing with sorted input.
-	 */
-	result = true;
-
-	for (i = numCols; --i >= 0;)
-	{
-		AttrNumber	att = matchColIdx[i];
-		Datum		attr1,
-					attr2;
-		bool		isNull1,
-					isNull2;
-
-		attr1 = slot_getattr(slot1, att, &isNull1);
-
-		attr2 = slot_getattr(slot2, att, &isNull2);
-
-		if (isNull1 != isNull2)
-		{
-			result = false;		/* one null and one not; they aren't equal */
-			break;
-		}
-
-		if (isNull1)
-			continue;			/* both are null, treat as equal */
-
-		/* Apply the type-specific equality function */
-
-		if (!DatumGetBool(FunctionCall2(&eqfunctions[i],
-										attr1, attr2)))
-		{
-			result = false;		/* they aren't equal */
-			break;
-		}
-	}
-
-	MemoryContextSwitchTo(oldContext);
-
-	return result;
-}
-
-/*
- * execTuplesUnequal
- *		Return true if two tuples are definitely unequal in the indicated
- *		fields.
- *
- * Nulls are neither equal nor unequal to anything else.  A true result
- * is obtained only if there are non-null fields that compare not-equal.
- *
- * Parameters are identical to execTuplesMatch.
+ * execTuplesMatchPrepare
+ *		Build expression that can be evaluated using ExecQual(), returning
+ *		whether an ExprContext's inner/outer tuples are NOT DISTINCT
  */
-bool
-execTuplesUnequal(TupleTableSlot *slot1,
-				  TupleTableSlot *slot2,
+ExprState *
+execTuplesMatchPrepare(TupleDesc desc,
 					   int numCols,
-				  AttrNumber *matchColIdx,
-				  FmgrInfo *eqfunctions,
-				  MemoryContext evalContext)
+					   AttrNumber *keyColIdx,
+					   Oid *eqOperators,
+					   PlanState *parent)
 {
-	MemoryContext oldContext;
-	bool		result;
+	Oid		   *eqFunctions = (Oid *) palloc(numCols * sizeof(Oid));
 	int			i;
+	ExprState  *expr;
 
-	/* Reset and switch into the temp context. */
-	MemoryContextReset(evalContext);
-	oldContext = MemoryContextSwitchTo(evalContext);
-
-	/*
-	 * We cannot report a match without checking all the fields, but we can
-	 * report a non-match as soon as we find unequal fields.  So, start
-	 * comparing at the last field (least significant sort key). That's the
-	 * most likely to be different if we are dealing with sorted input.
-	 */
-	result = false;
-
-	for (i = numCols; --i >= 0;)
-	{
-		AttrNumber	att = matchColIdx[i];
-		Datum		attr1,
-					attr2;
-		bool		isNull1,
-					isNull2;
-
-		attr1 = slot_getattr(slot1, att, &isNull1);
-
-		if (isNull1)
-			continue;			/* can't prove anything here */
-
-		attr2 = slot_getattr(slot2, att, &isNull2);
-
-		if (isNull2)
-			continue;			/* can't prove anything here */
-
-		/* Apply the type-specific equality function */
-
-		if (!DatumGetBool(FunctionCall2(&eqfunctions[i],
-										attr1, attr2)))
-		{
-			result = true;		/* they are unequal */
-			break;
-		}
-	}
-
-	MemoryContextSwitchTo(oldContext);
-
-	return result;
-}
-
-
-/*
- * execTuplesMatchPrepare
- *		Look up the equality functions needed for execTuplesMatch or
- *		execTuplesUnequal, given an array of equality operator OIDs.
- *
- * The result is a palloc'd array.
- */
-FmgrInfo *
-execTuplesMatchPrepare(int numCols,
-					   Oid *eqOperators)
-{
-	FmgrInfo   *eqFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
-	int			i;
+	if (numCols == 0)
+		return NULL;
 
+	/* lookup equality functions */
 	for (i = 0; i < numCols; i++)
-	{
-		Oid			eq_opr = eqOperators[i];
-		Oid			eq_function;
+		eqFunctions[i] = get_opcode(eqOperators[i]);
 
-		eq_function = get_opcode(eq_opr);
-		fmgr_info(eq_function, &eqFunctions[i]);
-	}
+	/* build actual expression */
+	expr = ExecBuildGroupingEqual(desc, desc, numCols, keyColIdx, eqFunctions,
+								  parent);
 
-	return eqFunctions;
+	return expr;
 }
 
 /*
@@ -233,12 +94,12 @@ execTuplesMatchPrepare(int numCols,
 void
 execTuplesHashPrepare(int numCols,
 					  Oid *eqOperators,
-					  FmgrInfo **eqFunctions,
+					  Oid **eqFuncOids,
 					  FmgrInfo **hashFunctions)
 {
 	int			i;
 
-	*eqFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
+	*eqFuncOids = (Oid *) palloc(numCols * sizeof(Oid));
 	*hashFunctions = (FmgrInfo *) palloc(numCols * sizeof(FmgrInfo));
 
 	for (i = 0; i < numCols; i++)
@@ -255,7 +116,7 @@ execTuplesHashPrepare(int numCols,
 				 eq_opr);
 		/* We're not supporting cross-type cases here */
 		Assert(left_hash_function == right_hash_function);
-		fmgr_info(eq_function, &(*eqFunctions)[i]);
+		(*eqFuncOids)[i] = eq_function;
 		fmgr_info(right_hash_function, &(*hashFunctions)[i]);
 	}
 }
@@ -288,8 +149,10 @@ execTuplesHashPrepare(int numCols,
  * storage that will live as long as the hashtable does.
  */
 TupleHashTable
-BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
-					FmgrInfo *eqfunctions,
+BuildTupleHashTable(PlanState *parent,
+					TupleDesc inputDesc,
+					int numCols, AttrNumber *keyColIdx,
+					Oid *eqfuncoids,
 					FmgrInfo *hashfunctions,
 					long nbuckets, Size additionalsize,
 					MemoryContext tablecxt, MemoryContext tempcxt,
@@ -297,6 +160,7 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 {
 	TupleHashTable hashtable;
 	Size		entrysize = sizeof(TupleHashEntryData) + additionalsize;
+	MemoryContext oldcontext;
 
 	Assert(nbuckets > 0);
 
@@ -309,14 +173,13 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 	hashtable->numCols = numCols;
 	hashtable->keyColIdx = keyColIdx;
 	hashtable->tab_hash_funcs = hashfunctions;
-	hashtable->tab_eq_funcs = eqfunctions;
 	hashtable->tablecxt = tablecxt;
 	hashtable->tempcxt = tempcxt;
 	hashtable->entrysize = entrysize;
 	hashtable->tableslot = NULL;	/* will be made on first lookup */
 	hashtable->inputslot = NULL;
 	hashtable->in_hash_funcs = NULL;
-	hashtable->cur_eq_funcs = NULL;
+	hashtable->cur_eq_func = NULL;
 
 	/*
 	 * If parallelism is in use, even if the master backend is performing the
@@ -333,6 +196,24 @@ BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
 
 	hashtable->hashtab = tuplehash_create(tablecxt, nbuckets, hashtable);
 
+	oldcontext = MemoryContextSwitchTo(hashtable->tablecxt);
+
+	/*
+	 * We copy the input tuple descriptor just for safety --- we assume all
+	 * input tuples will have equivalent descriptors.
+	 */
+	hashtable->tableslot = MakeSingleTupleTableSlot(CreateTupleDescCopy(inputDesc));
+
+	/* build comparator for all columns */
+	hashtable->tab_eq_func = ExecBuildGroupingEqual(inputDesc, inputDesc,
+													numCols,
+													keyColIdx, eqfuncoids,
+													parent);
+
+	MemoryContextSwitchTo(oldcontext);
+
+	hashtable->exprcontext = CreateExprContext(parent->state);
+
 	return hashtable;
 }
 
@@ -357,29 +238,13 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
 	bool		found;
 	MinimalTuple key;
 
-	/* If first time through, clone the input slot to make table slot */
-	if (hashtable->tableslot == NULL)
-	{
-		TupleDesc	tupdesc;
-
-		oldContext = MemoryContextSwitchTo(hashtable->tablecxt);
-
-		/*
-		 * We copy the input tuple descriptor just for safety --- we assume
-		 * all input tuples will have equivalent descriptors.
-		 */
-		tupdesc = CreateTupleDescCopy(slot->tts_tupleDescriptor);
-		hashtable->tableslot = MakeSingleTupleTableSlot(tupdesc);
-		MemoryContextSwitchTo(oldContext);
-	}
-
 	/* Need to run the hash functions in short-lived context */
 	oldContext = MemoryContextSwitchTo(hashtable->tempcxt);
 
 	/* set up data needed by hash and match functions */
 	hashtable->inputslot = slot;
 	hashtable->in_hash_funcs = hashtable->tab_hash_funcs;
-	hashtable->cur_eq_funcs = hashtable->tab_eq_funcs;
+	hashtable->cur_eq_func = hashtable->tab_eq_func;
 
 	key = NULL;					/* flag to reference inputslot */
 
@@ -424,7 +289,7 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
  */
 TupleHashEntry
 FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
-				   FmgrInfo *eqfunctions,
+				   ExprState *eqcomp,
 				   FmgrInfo *hashfunctions)
 {
 	TupleHashEntry entry;
@@ -437,7 +302,7 @@ FindTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
 	/* Set up data needed by hash and match functions */
 	hashtable->inputslot = slot;
 	hashtable->in_hash_funcs = hashfunctions;
-	hashtable->cur_eq_funcs = eqfunctions;
+	hashtable->cur_eq_func = eqcomp;
 
 	/* Search the hash table */
 	key = NULL;					/* flag to reference inputslot */
@@ -524,9 +389,6 @@ TupleHashTableHash(struct tuplehash_hash *tb, const MinimalTuple tuple)
  * See whether two tuples (presumably of the same hash value) match
  *
  * As above, the passed pointers are pointers to TupleHashEntryData.
- *
- * Also, the caller must select an appropriate memory context for running
- * the compare functions.  (dynahash.c doesn't change CurrentMemoryContext.)
  */
 static int
 TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const MinimalTuple tuple2)
@@ -534,6 +396,7 @@ TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const
 	TupleTableSlot *slot1;
 	TupleTableSlot *slot2;
 	TupleHashTable hashtable = (TupleHashTable) tb->private_data;
+	ExprContext *econtext = hashtable->exprcontext;
 
 	/*
 	 * We assume that simplehash.h will only ever call us with the first
@@ -548,13 +411,7 @@ TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const
 	slot2 = hashtable->inputslot;
 
 	/* For crosstype comparisons, the inputslot must be first */
-	if (execTuplesMatch(slot2,
-						slot1,
-						hashtable->numCols,
-						hashtable->keyColIdx,
-						hashtable->cur_eq_funcs,
-						hashtable->tempcxt))
-		return 0;
-	else
-		return 1;
+	econtext->ecxt_innertuple = slot2;
+	econtext->ecxt_outertuple = slot1;
+	return !ExecQualAndReset(hashtable->cur_eq_func, econtext);
 }

src/backend/executor/nodeAgg.c

@@ -755,7 +755,7 @@ process_ordered_aggregate_single(AggState *aggstate,
 			((oldIsNull && *isNull) ||
 			 (!oldIsNull && !*isNull &&
 			  oldAbbrevVal == newAbbrevVal &&
-			  DatumGetBool(FunctionCall2(&pertrans->equalfns[0],
+			  DatumGetBool(FunctionCall2(&pertrans->equalfnOne,
 										 oldVal, *newVal)))))
 		{
 			/* equal to prior, so forget this one */
@@ -802,7 +802,7 @@ process_ordered_aggregate_multi(AggState *aggstate,
 								AggStatePerTrans pertrans,
 								AggStatePerGroup pergroupstate)
 {
-	MemoryContext workcontext = aggstate->tmpcontext->ecxt_per_tuple_memory;
+	ExprContext *tmpcontext = aggstate->tmpcontext;
 	FunctionCallInfo fcinfo = &pertrans->transfn_fcinfo;
 	TupleTableSlot *slot1 = pertrans->sortslot;
 	TupleTableSlot *slot2 = pertrans->uniqslot;
@@ -811,6 +811,7 @@ process_ordered_aggregate_multi(AggState *aggstate,
 	Datum		newAbbrevVal = (Datum) 0;
 	Datum		oldAbbrevVal = (Datum) 0;
 	bool		haveOldValue = false;
+	TupleTableSlot *save = aggstate->tmpcontext->ecxt_outertuple;
 	int			i;
 
 	tuplesort_performsort(pertrans->sortstates[aggstate->current_set]);
@@ -824,22 +825,20 @@ process_ordered_aggregate_multi(AggState *aggstate,
 	{
 		CHECK_FOR_INTERRUPTS();
 
-		/*
-		 * Extract the first numTransInputs columns as datums to pass to the
-		 * transfn.  (This will help execTuplesMatch too, so we do it
-		 * immediately.)
-		 */
-		slot_getsomeattrs(slot1, numTransInputs);
+		tmpcontext->ecxt_outertuple = slot1;
+		tmpcontext->ecxt_innertuple = slot2;
 
 		if (numDistinctCols == 0 ||
 			!haveOldValue ||
 			newAbbrevVal != oldAbbrevVal ||
-			!execTuplesMatch(slot1, slot2,
-							 numDistinctCols,
-							 pertrans->sortColIdx,
-							 pertrans->equalfns,
-							 workcontext))
+			!ExecQual(pertrans->equalfnMulti, tmpcontext))
 		{
+			/*
+			 * Extract the first numTransInputs columns as datums to pass to
+			 * the transfn.
+			 */
+			slot_getsomeattrs(slot1, numTransInputs);
+
 			/* Load values into fcinfo */
 			/* Start from 1, since the 0th arg will be the transition value */
 			for (i = 0; i < numTransInputs; i++)
@@ -857,15 +856,14 @@ process_ordered_aggregate_multi(AggState *aggstate,
 
 				slot2 = slot1;
 				slot1 = tmpslot;
-				/* avoid execTuplesMatch() calls by reusing abbreviated keys */
+				/* avoid ExecQual() calls by reusing abbreviated keys */
 				oldAbbrevVal = newAbbrevVal;
 				haveOldValue = true;
 			}
 		}
 
-		/* Reset context each time, unless execTuplesMatch did it for us */
-		if (numDistinctCols == 0)
-			MemoryContextReset(workcontext);
+		/* Reset context each time */
+		ResetExprContext(tmpcontext);
 
 		ExecClearTuple(slot1);
 	}
@@ -875,6 +873,9 @@ process_ordered_aggregate_multi(AggState *aggstate,
 
 	tuplesort_end(pertrans->sortstates[aggstate->current_set]);
 	pertrans->sortstates[aggstate->current_set] = NULL;
+
+	/* restore previous slot, potentially in use for grouping sets */
+	tmpcontext->ecxt_outertuple = save;
 }
 
 /*
@@ -1276,9 +1277,11 @@ build_hash_table(AggState *aggstate)
 
 		Assert(perhash->aggnode->numGroups > 0);
 
-		perhash->hashtable = BuildTupleHashTable(perhash->numCols,
+		perhash->hashtable = BuildTupleHashTable(&aggstate->ss.ps,
+												 perhash->hashslot->tts_tupleDescriptor,
+												 perhash->numCols,
 												 perhash->hashGrpColIdxHash,
-												 perhash->eqfunctions,
+												 perhash->eqfuncoids,
 												 perhash->hashfunctions,
 												 perhash->aggnode->numGroups,
 												 additionalsize,
@@ -1314,6 +1317,7 @@ find_hash_columns(AggState *aggstate)
 	Bitmapset  *base_colnos;
 	List	   *outerTlist = outerPlanState(aggstate)->plan->targetlist;
 	int			numHashes = aggstate->num_hashes;
+	EState	   *estate = aggstate->ss.ps.state;
 	int			j;
 
 	/* Find Vars that will be needed in tlist and qual */
@@ -1393,6 +1397,12 @@ find_hash_columns(AggState *aggstate)
 		}
 
 		hashDesc = ExecTypeFromTL(hashTlist, false);
+
+		execTuplesHashPrepare(perhash->numCols,
+							  perhash->aggnode->grpOperators,
+							  &perhash->eqfuncoids,
+							  &perhash->hashfunctions);
+		perhash->hashslot = ExecAllocTableSlot(&estate->es_tupleTable);
 		ExecSetSlotDescriptor(perhash->hashslot, hashDesc);
 
 		list_free(hashTlist);
@@ -1694,17 +1704,14 @@ agg_retrieve_direct(AggState *aggstate)
 		 *		of the next grouping set
 		 *----------
 		 */
+		tmpcontext->ecxt_innertuple = econtext->ecxt_outertuple;
 		if (aggstate->input_done ||
 			(node->aggstrategy != AGG_PLAIN &&
 			 aggstate->projected_set != -1 &&
 			 aggstate->projected_set < (numGroupingSets - 1) &&
 			 nextSetSize > 0 &&
-			 !execTuplesMatch(econtext->ecxt_outertuple,
-							  tmpcontext->ecxt_outertuple,
-							  nextSetSize,
-							  node->grpColIdx,
-							  aggstate->phase->eqfunctions,
-							  tmpcontext->ecxt_per_tuple_memory)))
+			 !ExecQualAndReset(aggstate->phase->eqfunctions[nextSetSize - 1],
+							   tmpcontext)))
 		{
 			aggstate->projected_set += 1;
 
@@ -1847,12 +1854,9 @@ agg_retrieve_direct(AggState *aggstate)
 					 */
 					if (node->aggstrategy != AGG_PLAIN)
 					{
-						if (!execTuplesMatch(firstSlot,
-											 outerslot,
-											 node->numCols,
-											 node->grpColIdx,
-											 aggstate->phase->eqfunctions,
-											 tmpcontext->ecxt_per_tuple_memory))
+						tmpcontext->ecxt_innertuple = firstSlot;
+						if (!ExecQual(aggstate->phase->eqfunctions[node->numCols - 1],
+									  tmpcontext))
 						{
 							aggstate->grp_firstTuple = ExecCopySlotTuple(outerslot);
 							break;
@@ -2078,6 +2082,7 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 	AggStatePerGroup *pergroups;
 	Plan	   *outerPlan;
 	ExprContext *econtext;
+	TupleDesc	scanDesc;
 	int			numaggs,
 				transno,
 				aggno;
@@ -2233,9 +2238,9 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 	 * initialize source tuple type.
 	 */
 	ExecAssignScanTypeFromOuterPlan(&aggstate->ss);
+	scanDesc = aggstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
 	if (node->chain)
-		ExecSetSlotDescriptor(aggstate->sort_slot,
-							  aggstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor);
+		ExecSetSlotDescriptor(aggstate->sort_slot, scanDesc);
 
 	/*
 	 * Initialize result tuple type and projection info.
@@ -2355,11 +2360,43 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 			 */
 			if (aggnode->aggstrategy == AGG_SORTED)
 			{
+				int			i = 0;
+
 				Assert(aggnode->numCols > 0);
 
+				/*
+				 * Build a separate function for each subset of columns that
+				 * need to be compared.
+				 */
 				phasedata->eqfunctions =
-					execTuplesMatchPrepare(aggnode->numCols,
-										   aggnode->grpOperators);
+					(ExprState **) palloc0(aggnode->numCols * sizeof(ExprState *));
+
+				/* for each grouping set */
+				for (i = 0; i < phasedata->numsets; i++)
+				{
+					int		length = phasedata->gset_lengths[i];
+
+					if (phasedata->eqfunctions[length - 1] != NULL)
+						continue;
+
+					phasedata->eqfunctions[length - 1] =
+						execTuplesMatchPrepare(scanDesc,
+											   length,
+											   aggnode->grpColIdx,
+											   aggnode->grpOperators,
+											   (PlanState *) aggstate);
+				}
+
+				/* and for all grouped columns, unless already computed */
+				if (phasedata->eqfunctions[aggnode->numCols - 1] == NULL)
+				{
+					phasedata->eqfunctions[aggnode->numCols - 1] =
+						execTuplesMatchPrepare(scanDesc,
+											   aggnode->numCols,
+											   aggnode->grpColIdx,
+											   aggnode->grpOperators,
+											   (PlanState *) aggstate);
+				}
 			}
 
 			phasedata->aggnode = aggnode;
@@ -2412,16 +2449,6 @@ ExecInitAgg(Agg *node, EState *estate, int eflags)
 	 */
 	if (use_hashing)
 	{
-		for (i = 0; i < numHashes; ++i)
-		{
-			aggstate->perhash[i].hashslot = ExecInitExtraTupleSlot(estate);
-
-			execTuplesHashPrepare(aggstate->perhash[i].numCols,
-								  aggstate->perhash[i].aggnode->grpOperators,
-								  &aggstate->perhash[i].eqfunctions,
-								  &aggstate->perhash[i].hashfunctions);
-		}
-
 		/* this is an array of pointers, not structures */
 		aggstate->hash_pergroup = pergroups;
 
@@ -3101,24 +3128,28 @@ build_pertrans_for_aggref(AggStatePerTrans pertrans,
 
 	if (aggref->aggdistinct)
 	{
+		Oid		   *ops;
+
 		Assert(numArguments > 0);
+		Assert(list_length(aggref->aggdistinct) == numDistinctCols);
 
-		/*
-		 * We need the equal function for each DISTINCT comparison we will
-		 * make.
-		 */
-		pertrans->equalfns =
-			(FmgrInfo *) palloc(numDistinctCols * sizeof(FmgrInfo));
+		ops = palloc(numDistinctCols * sizeof(Oid));
 
 		i = 0;
 		foreach(lc, aggref->aggdistinct)
-		{
-			SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc);
+			ops[i++] = ((SortGroupClause *) lfirst(lc))->eqop;
 
-			fmgr_info(get_opcode(sortcl->eqop), &pertrans->equalfns[i]);
-			i++;
-		}
-		Assert(i == numDistinctCols);
+		/* lookup / build the necessary comparators */
+		if (numDistinctCols == 1)
+			fmgr_info(get_opcode(ops[0]), &pertrans->equalfnOne);
+		else
+			pertrans->equalfnMulti =
+				execTuplesMatchPrepare(pertrans->sortdesc,
+									   numDistinctCols,
+									   pertrans->sortColIdx,
+									   ops,
+									   &aggstate->ss.ps);
+		pfree(ops);
 	}
 
 	pertrans->sortstates = (Tuplesortstate **)

src/backend/executor/nodeGroup.c

@@ -25,6 +25,7 @@
 #include "executor/executor.h"
 #include "executor/nodeGroup.h"
 #include "miscadmin.h"
+#include "utils/memutils.h"
 
 
 /*
@@ -37,8 +38,6 @@ ExecGroup(PlanState *pstate)
 {
 	GroupState *node = castNode(GroupState, pstate);
 	ExprContext *econtext;
-	int			numCols;
-	AttrNumber *grpColIdx;
 	TupleTableSlot *firsttupleslot;
 	TupleTableSlot *outerslot;
 
@@ -50,8 +49,6 @@ ExecGroup(PlanState *pstate)
 	if (node->grp_done)
 		return NULL;
 	econtext = node->ss.ps.ps_ExprContext;
-	numCols = ((Group *) node->ss.ps.plan)->numCols;
-	grpColIdx = ((Group *) node->ss.ps.plan)->grpColIdx;
 
 	/*
 	 * The ScanTupleSlot holds the (copied) first tuple of each group.
@@ -59,7 +56,7 @@ ExecGroup(PlanState *pstate)
 	firsttupleslot = node->ss.ss_ScanTupleSlot;
 
 	/*
-	 * We need not call ResetExprContext here because execTuplesMatch will
+	 * We need not call ResetExprContext here because ExecQualAndReset() will
 	 * reset the per-tuple memory context once per input tuple.
 	 */
 
@@ -124,10 +121,9 @@ ExecGroup(PlanState *pstate)
 			 * Compare with first tuple and see if this tuple is of the same
 			 * group.  If so, ignore it and keep scanning.
 			 */
-			if (!execTuplesMatch(firsttupleslot, outerslot,
-								 numCols, grpColIdx,
-								 node->eqfunctions,
-								 econtext->ecxt_per_tuple_memory))
+			econtext->ecxt_innertuple = firsttupleslot;
+			econtext->ecxt_outertuple = outerslot;
+			if (!ExecQualAndReset(node->eqfunction, econtext))
 				break;
 		}
 
@@ -166,6 +162,7 @@ GroupState *
 ExecInitGroup(Group *node, EState *estate, int eflags)
 {
 	GroupState *grpstate;
+	AttrNumber *grpColIdx = grpColIdx = node->grpColIdx;
 
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -215,9 +212,12 @@ ExecInitGroup(Group *node, EState *estate, int eflags)
 	/*
 	 * Precompute fmgr lookup data for inner loop
 	 */
-	grpstate->eqfunctions =
-		execTuplesMatchPrepare(node->numCols,
-							   node->grpOperators);
+	grpstate->eqfunction =
+		execTuplesMatchPrepare(ExecGetResultType(outerPlanState(grpstate)),
+							   node->numCols,
+							   grpColIdx,
+							   node->grpOperators,
+							   &grpstate->ss.ps);
 
 	return grpstate;
 }

src/backend/executor/nodeRecursiveunion.c

@@ -32,13 +32,16 @@ static void
 build_hash_table(RecursiveUnionState *rustate)
 {
 	RecursiveUnion *node = (RecursiveUnion *) rustate->ps.plan;
+	TupleDesc	desc = ExecGetResultType(outerPlanState(rustate));
 
 	Assert(node->numCols > 0);
 	Assert(node->numGroups > 0);
 
-	rustate->hashtable = BuildTupleHashTable(node->numCols,
+	rustate->hashtable = BuildTupleHashTable(&rustate->ps,
+											 desc,
+											 node->numCols,
 											 node->dupColIdx,
-											 rustate->eqfunctions,
+											 rustate->eqfuncoids,
 											 rustate->hashfunctions,
 											 node->numGroups,
 											 0,
@@ -175,7 +178,7 @@ ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
 	rustate->ps.state = estate;
 	rustate->ps.ExecProcNode = ExecRecursiveUnion;
 
-	rustate->eqfunctions = NULL;
+	rustate->eqfuncoids = NULL;
 	rustate->hashfunctions = NULL;
 	rustate->hashtable = NULL;
 	rustate->tempContext = NULL;
@@ -250,7 +253,7 @@ ExecInitRecursiveUnion(RecursiveUnion *node, EState *estate, int eflags)
 	{
 		execTuplesHashPrepare(node->numCols,
 							  node->dupOperators,
-							  &rustate->eqfunctions,
+							  &rustate->eqfuncoids,
 							  &rustate->hashfunctions);
 		build_hash_table(rustate);
 	}

src/backend/executor/nodeSetOp.c

@@ -120,18 +120,22 @@ static void
 build_hash_table(SetOpState *setopstate)
 {
 	SetOp	   *node = (SetOp *) setopstate->ps.plan;
+	ExprContext *econtext = setopstate->ps.ps_ExprContext;
+	TupleDesc	desc = ExecGetResultType(outerPlanState(setopstate));
 
 	Assert(node->strategy == SETOP_HASHED);
 	Assert(node->numGroups > 0);
 
-	setopstate->hashtable = BuildTupleHashTable(node->numCols,
+	setopstate->hashtable = BuildTupleHashTable(&setopstate->ps,
+												desc,
+												node->numCols,
 												node->dupColIdx,
-												setopstate->eqfunctions,
+												setopstate->eqfuncoids,
 												setopstate->hashfunctions,
 												node->numGroups,
 												0,
 												setopstate->tableContext,
-												setopstate->tempContext,
+												econtext->ecxt_per_tuple_memory,
 												false);
 }
 
@@ -220,11 +224,11 @@ ExecSetOp(PlanState *pstate)
 static TupleTableSlot *
 setop_retrieve_direct(SetOpState *setopstate)
 {
-	SetOp	   *node = (SetOp *) setopstate->ps.plan;
 	PlanState  *outerPlan;
 	SetOpStatePerGroup pergroup;
 	TupleTableSlot *outerslot;
 	TupleTableSlot *resultTupleSlot;
+	ExprContext *econtext = setopstate->ps.ps_ExprContext;
 
 	/*
 	 * get state info from node
@@ -292,11 +296,10 @@ setop_retrieve_direct(SetOpState *setopstate)
 			/*
 			 * Check whether we've crossed a group boundary.
 			 */
-			if (!execTuplesMatch(resultTupleSlot,
-								 outerslot,
-								 node->numCols, node->dupColIdx,
-								 setopstate->eqfunctions,
-								 setopstate->tempContext))
+			econtext->ecxt_outertuple = resultTupleSlot;
+			econtext->ecxt_innertuple = outerslot;
+
+			if (!ExecQualAndReset(setopstate->eqfunction, econtext))
 			{
 				/*
 				 * Save the first input tuple of the next group.
@@ -338,6 +341,7 @@ setop_fill_hash_table(SetOpState *setopstate)
 	PlanState  *outerPlan;
 	int			firstFlag;
 	bool		in_first_rel PG_USED_FOR_ASSERTS_ONLY;
+	ExprContext *econtext = setopstate->ps.ps_ExprContext;
 
 	/*
 	 * get state info from node
@@ -404,8 +408,8 @@ setop_fill_hash_table(SetOpState *setopstate)
 				advance_counts((SetOpStatePerGroup) entry->additional, flag);
 		}
 
-		/* Must reset temp context after each hashtable lookup */
-		MemoryContextReset(setopstate->tempContext);
+		/* Must reset expression context after each hashtable lookup */
+		ResetExprContext(econtext);
 	}
 
 	setopstate->table_filled = true;
@@ -476,6 +480,7 @@ SetOpState *
 ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 {
 	SetOpState *setopstate;
+	TupleDesc	outerDesc;
 
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -488,7 +493,7 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	setopstate->ps.state = estate;
 	setopstate->ps.ExecProcNode = ExecSetOp;
 
-	setopstate->eqfunctions = NULL;
+	setopstate->eqfuncoids = NULL;
 	setopstate->hashfunctions = NULL;
 	setopstate->setop_done = false;
 	setopstate->numOutput = 0;
@@ -498,16 +503,9 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	setopstate->tableContext = NULL;
 
 	/*
-	 * Miscellaneous initialization
-	 *
-	 * SetOp nodes have no ExprContext initialization because they never call
-	 * ExecQual or ExecProject.  But they do need a per-tuple memory context
-	 * anyway for calling execTuplesMatch.
+	 * create expression context
 	 */
-	setopstate->tempContext =
-		AllocSetContextCreate(CurrentMemoryContext,
-							  "SetOp",
-							  ALLOCSET_DEFAULT_SIZES);
+	ExecAssignExprContext(estate, &setopstate->ps);
 
 	/*
 	 * If hashing, we also need a longer-lived context to store the hash
@@ -534,6 +532,7 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	if (node->strategy == SETOP_HASHED)
 		eflags &= ~EXEC_FLAG_REWIND;
 	outerPlanState(setopstate) = ExecInitNode(outerPlan(node), estate, eflags);
+	outerDesc = ExecGetResultType(outerPlanState(setopstate));
 
 	/*
 	 * setop nodes do no projections, so initialize projection info for this
@@ -550,12 +549,15 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	if (node->strategy == SETOP_HASHED)
 		execTuplesHashPrepare(node->numCols,
 							  node->dupOperators,
-							  &setopstate->eqfunctions,
+							  &setopstate->eqfuncoids,
 							  &setopstate->hashfunctions);
 	else
-		setopstate->eqfunctions =
-			execTuplesMatchPrepare(node->numCols,
-								   node->dupOperators);
+		setopstate->eqfunction =
+			execTuplesMatchPrepare(outerDesc,
+								   node->numCols,
+								   node->dupColIdx,
+								   node->dupOperators,
+								   &setopstate->ps);
 
 	if (node->strategy == SETOP_HASHED)
 	{
@@ -585,9 +587,9 @@ ExecEndSetOp(SetOpState *node)
 	ExecClearTuple(node->ps.ps_ResultTupleSlot);
 
 	/* free subsidiary stuff including hashtable */
-	MemoryContextDelete(node->tempContext);
 	if (node->tableContext)
 		MemoryContextDelete(node->tableContext);
+	ExecFreeExprContext(&node->ps);
 
 	ExecEndNode(outerPlanState(node));
 }

src/backend/executor/nodeSubplan.c

@@ -149,7 +149,7 @@ ExecHashSubPlan(SubPlanState *node,
 		if (node->havehashrows &&
 			FindTupleHashEntry(node->hashtable,
 							   slot,
-							   node->cur_eq_funcs,
+							   node->cur_eq_comp,
 							   node->lhs_hash_funcs) != NULL)
 		{
 			ExecClearTuple(slot);
@@ -494,9 +494,11 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 	if (nbuckets < 1)
 		nbuckets = 1;
 
-	node->hashtable = BuildTupleHashTable(ncols,
+	node->hashtable = BuildTupleHashTable(node->parent,
+										  node->descRight,
+										  ncols,
 										  node->keyColIdx,
-										  node->tab_eq_funcs,
+										  node->tab_eq_funcoids,
 										  node->tab_hash_funcs,
 										  nbuckets,
 										  0,
@@ -514,9 +516,11 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 			if (nbuckets < 1)
 				nbuckets = 1;
 		}
-		node->hashnulls = BuildTupleHashTable(ncols,
+		node->hashnulls = BuildTupleHashTable(node->parent,
+											  node->descRight,
+											  ncols,
 											  node->keyColIdx,
-											  node->tab_eq_funcs,
+											  node->tab_eq_funcoids,
 											  node->tab_hash_funcs,
 											  nbuckets,
 											  0,
@@ -598,6 +602,77 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
 	MemoryContextSwitchTo(oldcontext);
 }
 
+/*
+ * execTuplesUnequal
+ *		Return true if two tuples are definitely unequal in the indicated
+ *		fields.
+ *
+ * Nulls are neither equal nor unequal to anything else.  A true result
+ * is obtained only if there are non-null fields that compare not-equal.
+ *
+ * slot1, slot2: the tuples to compare (must have same columns!)
+ * numCols: the number of attributes to be examined
+ * matchColIdx: array of attribute column numbers
+ * eqFunctions: array of fmgr lookup info for the equality functions to use
+ * evalContext: short-term memory context for executing the functions
+ */
+static bool
+execTuplesUnequal(TupleTableSlot *slot1,
+				  TupleTableSlot *slot2,
+				  int numCols,
+				  AttrNumber *matchColIdx,
+				  FmgrInfo *eqfunctions,
+				  MemoryContext evalContext)
+{
+	MemoryContext oldContext;
+	bool		result;
+	int			i;
+
+	/* Reset and switch into the temp context. */
+	MemoryContextReset(evalContext);
+	oldContext = MemoryContextSwitchTo(evalContext);
+
+	/*
+	 * We cannot report a match without checking all the fields, but we can
+	 * report a non-match as soon as we find unequal fields.  So, start
+	 * comparing at the last field (least significant sort key). That's the
+	 * most likely to be different if we are dealing with sorted input.
+	 */
+	result = false;
+
+	for (i = numCols; --i >= 0;)
+	{
+		AttrNumber	att = matchColIdx[i];
+		Datum		attr1,
+					attr2;
+		bool		isNull1,
+					isNull2;
+
+		attr1 = slot_getattr(slot1, att, &isNull1);
+
+		if (isNull1)
+			continue;			/* can't prove anything here */
+
+		attr2 = slot_getattr(slot2, att, &isNull2);
+
+		if (isNull2)
+			continue;			/* can't prove anything here */
+
+		/* Apply the type-specific equality function */
+
+		if (!DatumGetBool(FunctionCall2(&eqfunctions[i],
+										attr1, attr2)))
+		{
+			result = true;		/* they are unequal */
+			break;
+		}
+	}
+
+	MemoryContextSwitchTo(oldContext);
+
+	return result;
+}
+
 /*
  * findPartialMatch: does the hashtable contain an entry that is not
  * provably distinct from the tuple?
@@ -719,6 +794,7 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 	sstate->hashtempcxt = NULL;
 	sstate->innerecontext = NULL;
 	sstate->keyColIdx = NULL;
+	sstate->tab_eq_funcoids = NULL;
 	sstate->tab_hash_funcs = NULL;
 	sstate->tab_eq_funcs = NULL;
 	sstate->lhs_hash_funcs = NULL;
@@ -757,7 +833,8 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 	{
 		int			ncols,
 					i;
-		TupleDesc	tupDesc;
+		TupleDesc	tupDescLeft;
+		TupleDesc	tupDescRight;
 		TupleTableSlot *slot;
 		List	   *oplist,
 				   *lefttlist,
@@ -815,6 +892,7 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 		Assert(list_length(oplist) == ncols);
 
 		lefttlist = righttlist = NIL;
+		sstate->tab_eq_funcoids = (Oid *) palloc(ncols * sizeof(Oid));
 		sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 		sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
 		sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
@@ -848,6 +926,7 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 			righttlist = lappend(righttlist, tle);
 
 			/* Lookup the equality function (potentially cross-type) */
+			sstate->tab_eq_funcoids[i - 1] = opexpr->opfuncid;
 			fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
 			fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
 
@@ -877,23 +956,34 @@ ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
 		 * (hack alert!).  The righthand expressions will be evaluated in our
 		 * own innerecontext.
 		 */
-		tupDesc = ExecTypeFromTL(lefttlist, false);
+		tupDescLeft = ExecTypeFromTL(lefttlist, false);
 		slot = ExecInitExtraTupleSlot(estate);
-		ExecSetSlotDescriptor(slot, tupDesc);
+		ExecSetSlotDescriptor(slot, tupDescLeft);
 		sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
 												   NULL,
 												   slot,
 												   parent,
 												   NULL);
 
-		tupDesc = ExecTypeFromTL(righttlist, false);
+		sstate->descRight = tupDescRight = ExecTypeFromTL(righttlist, false);
 		slot = ExecInitExtraTupleSlot(estate);
-		ExecSetSlotDescriptor(slot, tupDesc);
+		ExecSetSlotDescriptor(slot, tupDescRight);
 		sstate->projRight = ExecBuildProjectionInfo(righttlist,
 													sstate->innerecontext,
 													slot,
 													sstate->planstate,
 													NULL);
+
+		/*
+		 * Create comparator for lookups of rows in the table (potentially
+		 *  across-type comparison).
+		 */
+		sstate->cur_eq_comp = ExecBuildGroupingEqual(tupDescLeft, tupDescRight,
+													 ncols,
+													 sstate->keyColIdx,
+													 sstate->tab_eq_funcoids,
+													 parent);
+
 	}
 
 	return sstate;

src/backend/executor/nodeUnique.c

@@ -47,7 +47,7 @@ static TupleTableSlot *			/* return: a tuple or NULL */
 ExecUnique(PlanState *pstate)
 {
 	UniqueState *node = castNode(UniqueState, pstate);
-	Unique	   *plannode = (Unique *) node->ps.plan;
+	ExprContext *econtext = node->ps.ps_ExprContext;
 	TupleTableSlot *resultTupleSlot;
 	TupleTableSlot *slot;
 	PlanState  *outerPlan;
@@ -89,10 +89,9 @@ ExecUnique(PlanState *pstate)
 		 * If so then we loop back and fetch another new tuple from the
 		 * subplan.
 		 */
-		if (!execTuplesMatch(slot, resultTupleSlot,
-							 plannode->numCols, plannode->uniqColIdx,
-							 node->eqfunctions,
-							 node->tempContext))
+		econtext->ecxt_innertuple = slot;
+		econtext->ecxt_outertuple = resultTupleSlot;
+		if (!ExecQualAndReset(node->eqfunction, econtext))
 			break;
 	}
 
@@ -129,16 +128,9 @@ ExecInitUnique(Unique *node, EState *estate, int eflags)
 	uniquestate->ps.ExecProcNode = ExecUnique;
 
 	/*
-	 * Miscellaneous initialization
-	 *
-	 * Unique nodes have no ExprContext initialization because they never call
-	 * ExecQual or ExecProject.  But they do need a per-tuple memory context
-	 * anyway for calling execTuplesMatch.
+	 * create expression context
 	 */
-	uniquestate->tempContext =
-		AllocSetContextCreate(CurrentMemoryContext,
-							  "Unique",
-							  ALLOCSET_DEFAULT_SIZES);
+	ExecAssignExprContext(estate, &uniquestate->ps);
 
 	/*
 	 * Tuple table initialization
@@ -160,9 +152,12 @@ ExecInitUnique(Unique *node, EState *estate, int eflags)
 	/*
 	 * Precompute fmgr lookup data for inner loop
 	 */
-	uniquestate->eqfunctions =
-		execTuplesMatchPrepare(node->numCols,
-							   node->uniqOperators);
+	uniquestate->eqfunction =
+		execTuplesMatchPrepare(ExecGetResultType(outerPlanState(uniquestate)),
+							   node->numCols,
+							   node->uniqColIdx,
+							   node->uniqOperators,
+							   &uniquestate->ps);
 
 	return uniquestate;
 }
@@ -180,7 +175,7 @@ ExecEndUnique(UniqueState *node)
 	/* clean up tuple table */
 	ExecClearTuple(node->ps.ps_ResultTupleSlot);
 
-	MemoryContextDelete(node->tempContext);
+	ExecFreeExprContext(&node->ps);
 
 	ExecEndNode(outerPlanState(node));
 }

src/backend/executor/nodeWindowAgg.c

@@ -1272,12 +1272,13 @@ spool_tuples(WindowAggState *winstate, int64 pos)
 
 		if (node->partNumCols > 0)
 		{
+			ExprContext *econtext = winstate->tmpcontext;
+
+			econtext->ecxt_innertuple = winstate->first_part_slot;
+			econtext->ecxt_outertuple = outerslot;
+
 			/* Check if this tuple still belongs to the current partition */
-			if (!execTuplesMatch(winstate->first_part_slot,
-								 outerslot,
-								 node->partNumCols, node->partColIdx,
-								 winstate->partEqfunctions,
-								 winstate->tmpcontext->ecxt_per_tuple_memory))
+			if (!ExecQualAndReset(winstate->partEqfunction, econtext))
 			{
 				/*
 				 * end of partition; copy the tuple for the next cycle.
@@ -2245,6 +2246,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 				wfuncno,
 				numaggs,
 				aggno;
+	TupleDesc	scanDesc;
 	ListCell   *l;
 
 	/* check for unsupported flags */
@@ -2327,6 +2329,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 	 * store in the tuplestore and use in all our working slots).
 	 */
 	ExecAssignScanTypeFromOuterPlan(&winstate->ss);
+	scanDesc = winstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
 
 	ExecSetSlotDescriptor(winstate->first_part_slot,
 						  winstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor);
@@ -2351,11 +2354,20 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 
 	/* Set up data for comparing tuples */
 	if (node->partNumCols > 0)
-		winstate->partEqfunctions = execTuplesMatchPrepare(node->partNumCols,
-														   node->partOperators);
+		winstate->partEqfunction =
+			execTuplesMatchPrepare(scanDesc,
+								   node->partNumCols,
+								   node->partColIdx,
+								   node->partOperators,
+								   &winstate->ss.ps);
+
 	if (node->ordNumCols > 0)
-		winstate->ordEqfunctions = execTuplesMatchPrepare(node->ordNumCols,
-														  node->ordOperators);
+		winstate->ordEqfunction =
+			execTuplesMatchPrepare(scanDesc,
+								   node->ordNumCols,
+								   node->ordColIdx,
+								   node->ordOperators,
+								   &winstate->ss.ps);
 
 	/*
 	 * WindowAgg nodes use aggvalues and aggnulls as well as Agg nodes.
@@ -2879,15 +2891,15 @@ are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 		  TupleTableSlot *slot2)
 {
 	WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
+	ExprContext *econtext = winstate->tmpcontext;
 
 	/* If no ORDER BY, all rows are peers with each other */
 	if (node->ordNumCols == 0)
 		return true;
 
-	return execTuplesMatch(slot1, slot2,
-						   node->ordNumCols, node->ordColIdx,
-						   winstate->ordEqfunctions,
-						   winstate->tmpcontext->ecxt_per_tuple_memory);
+	econtext->ecxt_outertuple = slot1;
+	econtext->ecxt_innertuple = slot2;
+	return ExecQualAndReset(winstate->ordEqfunction, econtext);
 }
 
 /*

src/backend/utils/adt/orderedsetaggs.c

@@ -27,6 +27,7 @@
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
+#include "utils/memutils.h"
 #include "utils/timestamp.h"
 #include "utils/tuplesort.h"
 
@@ -54,6 +55,8 @@ typedef struct OSAPerQueryState
 	Aggref	   *aggref;
 	/* Memory context containing this struct and other per-query data: */
 	MemoryContext qcontext;
+	/* Context for expression evaluation */
+	ExprContext *econtext;
 	/* Do we expect multiple final-function calls within one group? */
 	bool		rescan_needed;
 
@@ -71,7 +74,7 @@ typedef struct OSAPerQueryState
 	Oid		   *sortCollations;
 	bool	   *sortNullsFirsts;
 	/* Equality operator call info, created only if needed: */
-	FmgrInfo   *equalfns;
+	ExprState  *compareTuple;
 
 	/* These fields are used only when accumulating datums: */
 
@@ -1287,6 +1290,8 @@ hypothetical_cume_dist_final(PG_FUNCTION_ARGS)
 Datum
 hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 {
+	ExprContext *econtext;
+	ExprState  *compareTuple;
 	int			nargs = PG_NARGS() - 1;
 	int64		rank = 1;
 	int64		duplicate_count = 0;
@@ -1294,12 +1299,9 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 	int			numDistinctCols;
 	Datum		abbrevVal = (Datum) 0;
 	Datum		abbrevOld = (Datum) 0;
-	AttrNumber *sortColIdx;
-	FmgrInfo   *equalfns;
 	TupleTableSlot *slot;
 	TupleTableSlot *extraslot;
 	TupleTableSlot *slot2;
-	MemoryContext tmpcontext;
 	int			i;
 
 	Assert(AggCheckCallContext(fcinfo, NULL) == AGG_CONTEXT_AGGREGATE);
@@ -1309,6 +1311,9 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 		PG_RETURN_INT64(rank);
 
 	osastate = (OSAPerGroupState *) PG_GETARG_POINTER(0);
+	econtext = osastate->qstate->econtext;
+	if (!econtext)
+		osastate->qstate->econtext = econtext = CreateStandaloneExprContext();
 
 	/* Adjust nargs to be the number of direct (or aggregated) args */
 	if (nargs % 2 != 0)
@@ -1323,26 +1328,22 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 	 */
 	numDistinctCols = osastate->qstate->numSortCols - 1;
 
-	/* Look up the equality function(s), if we didn't already */
-	equalfns = osastate->qstate->equalfns;
-	if (equalfns == NULL)
+	/* Build tuple comparator, if we didn't already */
+	compareTuple = osastate->qstate->compareTuple;
+	if (compareTuple == NULL)
 	{
-		MemoryContext qcontext = osastate->qstate->qcontext;
+		AttrNumber *sortColIdx = osastate->qstate->sortColIdx;
+		MemoryContext oldContext;
 
-		equalfns = (FmgrInfo *)
-			MemoryContextAlloc(qcontext, numDistinctCols * sizeof(FmgrInfo));
-		for (i = 0; i < numDistinctCols; i++)
-		{
-			fmgr_info_cxt(get_opcode(osastate->qstate->eqOperators[i]),
-						  &equalfns[i],
-						  qcontext);
-		}
-		osastate->qstate->equalfns = equalfns;
+		oldContext = MemoryContextSwitchTo(osastate->qstate->qcontext);
+		compareTuple = execTuplesMatchPrepare(osastate->qstate->tupdesc,
+											  numDistinctCols,
+											  sortColIdx,
+											  osastate->qstate->eqOperators,
+											  NULL);
+		MemoryContextSwitchTo(oldContext);
+		osastate->qstate->compareTuple = compareTuple;
 	}
-	sortColIdx = osastate->qstate->sortColIdx;
-
-	/* Get short-term context we can use for execTuplesMatch */
-	tmpcontext = AggGetTempMemoryContext(fcinfo);
 
 	/* because we need a hypothetical row, we can't share transition state */
 	Assert(!osastate->sort_done);
@@ -1385,19 +1386,18 @@ hypothetical_dense_rank_final(PG_FUNCTION_ARGS)
 			break;
 
 		/* count non-distinct tuples */
+		econtext->ecxt_outertuple = slot;
+		econtext->ecxt_innertuple = slot2;
+
 		if (!TupIsNull(slot2) &&
 			abbrevVal == abbrevOld &&
-			execTuplesMatch(slot, slot2,
-							numDistinctCols,
-							sortColIdx,
-							equalfns,
-							tmpcontext))
+			ExecQualAndReset(compareTuple, econtext))
 			duplicate_count++;
 
 		tmpslot = slot2;
 		slot2 = slot;
 		slot = tmpslot;
-		/* avoid execTuplesMatch() calls by reusing abbreviated keys */
+		/* avoid ExecQual() calls by reusing abbreviated keys */
 		abbrevOld = abbrevVal;
 
 		rank++;

src/include/executor/execExpr.h

@@ -148,6 +148,7 @@ typedef enum ExprEvalOp
 	/* evaluate assorted special-purpose expression types */
 	EEOP_IOCOERCE,
 	EEOP_DISTINCT,
+	EEOP_NOT_DISTINCT,
 	EEOP_NULLIF,
 	EEOP_SQLVALUEFUNCTION,
 	EEOP_CURRENTOFEXPR,

src/include/executor/executor.h

@@ -113,26 +113,19 @@ extern bool execCurrentOf(CurrentOfExpr *cexpr,
 /*
  * prototypes from functions in execGrouping.c
  */
-extern bool execTuplesMatch(TupleTableSlot *slot1,
-				TupleTableSlot *slot2,
+extern ExprState *execTuplesMatchPrepare(TupleDesc desc,
 					   int numCols,
-				AttrNumber *matchColIdx,
-				FmgrInfo *eqfunctions,
-				MemoryContext evalContext);
-extern bool execTuplesUnequal(TupleTableSlot *slot1,
-				  TupleTableSlot *slot2,
-				  int numCols,
-				  AttrNumber *matchColIdx,
-				  FmgrInfo *eqfunctions,
-				  MemoryContext evalContext);
-extern FmgrInfo *execTuplesMatchPrepare(int numCols,
-					   Oid *eqOperators);
+					   AttrNumber *keyColIdx,
+					   Oid *eqOperators,
+					   PlanState *parent);
 extern void execTuplesHashPrepare(int numCols,
 					  Oid *eqOperators,
-					  FmgrInfo **eqFunctions,
+					  Oid **eqFuncOids,
 					  FmgrInfo **hashFunctions);
-extern TupleHashTable BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
-					FmgrInfo *eqfunctions,
+extern TupleHashTable BuildTupleHashTable(PlanState *parent,
+					TupleDesc inputDesc,
+					int numCols, AttrNumber *keyColIdx,
+					Oid *eqfuncoids,
 					FmgrInfo *hashfunctions,
 					long nbuckets, Size additionalsize,
 					MemoryContext tablecxt,
@@ -142,7 +135,7 @@ extern TupleHashEntry LookupTupleHashEntry(TupleHashTable hashtable,
 					 bool *isnew);
 extern TupleHashEntry FindTupleHashEntry(TupleHashTable hashtable,
 				   TupleTableSlot *slot,
-				   FmgrInfo *eqfunctions,
+				   ExprState *eqcomp,
 				   FmgrInfo *hashfunctions);
 
 /*
@@ -257,6 +250,11 @@ extern ExprState *ExecInitCheck(List *qual, PlanState *parent);
 extern List *ExecInitExprList(List *nodes, PlanState *parent);
 extern ExprState *ExecBuildAggTrans(AggState *aggstate, struct AggStatePerPhaseData *phase,
 				  bool doSort, bool doHash);
+extern ExprState *ExecBuildGroupingEqual(TupleDesc ldesc, TupleDesc rdesc,
+					   int numCols,
+					   AttrNumber *keyColIdx,
+					   Oid *eqfunctions,
+					   PlanState *parent);
 extern ProjectionInfo *ExecBuildProjectionInfo(List *targetList,
 						ExprContext *econtext,
 						TupleTableSlot *slot,

src/include/executor/nodeAgg.h

@@ -102,11 +102,12 @@ typedef struct AggStatePerTransData
 	bool	   *sortNullsFirst;
 
 	/*
-	 * fmgr lookup data for input columns' equality operators --- only
-	 * set/used when aggregate has DISTINCT flag.  Note that these are in
-	 * order of sort column index, not parameter index.
+	 * Comparators for input columns --- only set/used when aggregate has
+	 * DISTINCT flag. equalfnOne version is used for single-column
+	 * commparisons, equalfnMulti for the case of multiple columns.
 	 */
-	FmgrInfo   *equalfns;		/* array of length numDistinctCols */
+	FmgrInfo	equalfnOne;
+	ExprState  *equalfnMulti;
 
 	/*
 	 * initial value from pg_aggregate entry
@@ -270,7 +271,8 @@ typedef struct AggStatePerPhaseData
 	int			numsets;		/* number of grouping sets (or 0) */
 	int		   *gset_lengths;	/* lengths of grouping sets */
 	Bitmapset **grouped_cols;	/* column groupings for rollup */
-	FmgrInfo   *eqfunctions;	/* per-grouping-field equality fns */
+	ExprState **eqfunctions;	/* expression returning equality, indexed by
+								 * nr of cols to compare */
 	Agg		   *aggnode;		/* Agg node for phase data */
 	Sort	   *sortnode;		/* Sort node for input ordering for phase */
 
@@ -290,7 +292,7 @@ typedef struct AggStatePerHashData
 	TupleHashIterator hashiter; /* for iterating through hash table */
 	TupleTableSlot *hashslot;	/* slot for loading hash table */
 	FmgrInfo   *hashfunctions;	/* per-grouping-field hash fns */
-	FmgrInfo   *eqfunctions;	/* per-grouping-field equality fns */
+	Oid		   *eqfuncoids;		/* per-grouping-field equality fns */
 	int			numCols;		/* number of hash key columns */
 	int			numhashGrpCols; /* number of columns in hash table */
 	int			largestGrpColIdx;	/* largest col required for hashing */

src/include/nodes/execnodes.h

@@ -594,10 +594,10 @@ typedef struct ExecAuxRowMark
  * Normally these are the only functions used, but FindTupleHashEntry()
  * supports searching a hashtable using cross-data-type hashing.  For that,
  * the caller must supply hash functions for the LHS datatype as well as
- * the cross-type equality operators to use.  in_hash_funcs and cur_eq_funcs
+ * the cross-type equality operators to use.  in_hash_funcs and cur_eq_func
  * are set to point to the caller's function arrays while doing such a search.
  * During LookupTupleHashEntry(), they point to tab_hash_funcs and
- * tab_eq_funcs respectively.
+ * tab_eq_func respectively.
  * ----------------------------------------------------------------
  */
 typedef struct TupleHashEntryData *TupleHashEntry;
@@ -625,7 +625,7 @@ typedef struct TupleHashTableData
 	int			numCols;		/* number of columns in lookup key */
 	AttrNumber *keyColIdx;		/* attr numbers of key columns */
 	FmgrInfo   *tab_hash_funcs; /* hash functions for table datatype(s) */
-	FmgrInfo   *tab_eq_funcs;	/* equality functions for table datatype(s) */
+	ExprState  *tab_eq_func;	/* comparator for table datatype(s) */
 	MemoryContext tablecxt;		/* memory context containing table */
 	MemoryContext tempcxt;		/* context for function evaluations */
 	Size		entrysize;		/* actual size to make each hash entry */
@@ -633,8 +633,9 @@ typedef struct TupleHashTableData
 	/* The following fields are set transiently for each table search: */
 	TupleTableSlot *inputslot;	/* current input tuple's slot */
 	FmgrInfo   *in_hash_funcs;	/* hash functions for input datatype(s) */
-	FmgrInfo   *cur_eq_funcs;	/* equality functions for input vs. table */
+	ExprState  *cur_eq_func;	/* comparator for for input vs. table */
 	uint32		hash_iv;		/* hash-function IV */
+	ExprContext *exprcontext;	/* expression context */
 }			TupleHashTableData;
 
 typedef tuplehash_iterator TupleHashIterator;
@@ -781,6 +782,7 @@ typedef struct SubPlanState
 	HeapTuple	curTuple;		/* copy of most recent tuple from subplan */
 	Datum		curArray;		/* most recent array from ARRAY() subplan */
 	/* these are used when hashing the subselect's output: */
+	TupleDesc	descRight;		/* subselect desc after projection */
 	ProjectionInfo *projLeft;	/* for projecting lefthand exprs */
 	ProjectionInfo *projRight;	/* for projecting subselect output */
 	TupleHashTable hashtable;	/* hash table for no-nulls subselect rows */
@@ -791,10 +793,12 @@ typedef struct SubPlanState
 	MemoryContext hashtempcxt;	/* temp memory context for hash tables */
 	ExprContext *innerecontext; /* econtext for computing inner tuples */
 	AttrNumber *keyColIdx;		/* control data for hash tables */
+	Oid		   *tab_eq_funcoids;/* equality func oids for table datatype(s) */
 	FmgrInfo   *tab_hash_funcs; /* hash functions for table datatype(s) */
 	FmgrInfo   *tab_eq_funcs;	/* equality functions for table datatype(s) */
 	FmgrInfo   *lhs_hash_funcs; /* hash functions for lefthand datatype(s) */
 	FmgrInfo   *cur_eq_funcs;	/* equality functions for LHS vs. table */
+	ExprState  *cur_eq_comp;	/* equality comparator for LHS vs. table */
 } SubPlanState;
 
 /* ----------------
@@ -1067,7 +1071,7 @@ typedef struct RecursiveUnionState
 	Tuplestorestate *working_table;
 	Tuplestorestate *intermediate_table;
 	/* Remaining fields are unused in UNION ALL case */
-	FmgrInfo   *eqfunctions;	/* per-grouping-field equality fns */
+	Oid		   *eqfuncoids;		/* per-grouping-field equality fns */
 	FmgrInfo   *hashfunctions;	/* per-grouping-field hash fns */
 	MemoryContext tempContext;	/* short-term context for comparisons */
 	TupleHashTable hashtable;	/* hash table for tuples already seen */
@@ -1795,7 +1799,7 @@ typedef struct SortState
 typedef struct GroupState
 {
 	ScanState	ss;				/* its first field is NodeTag */
-	FmgrInfo   *eqfunctions;	/* per-field lookup data for equality fns */
+	ExprState  *eqfunction;		/* equality function */
 	bool		grp_done;		/* indicates completion of Group scan */
 } GroupState;
 
@@ -1885,8 +1889,8 @@ typedef struct WindowAggState
 
 	WindowStatePerFunc perfunc; /* per-window-function information */
 	WindowStatePerAgg peragg;	/* per-plain-aggregate information */
-	FmgrInfo   *partEqfunctions;	/* equality funcs for partition columns */
-	FmgrInfo   *ordEqfunctions; /* equality funcs for ordering columns */
+	ExprState  *partEqfunction;	/* equality funcs for partition columns */
+	ExprState  *ordEqfunction; /* equality funcs for ordering columns */
 	Tuplestorestate *buffer;	/* stores rows of current partition */
 	int			current_ptr;	/* read pointer # for current row */
 	int			framehead_ptr;	/* read pointer # for frame head, if used */
@@ -1964,8 +1968,7 @@ typedef struct WindowAggState
 typedef struct UniqueState
 {
 	PlanState	ps;				/* its first field is NodeTag */
-	FmgrInfo   *eqfunctions;	/* per-field lookup data for equality fns */
-	MemoryContext tempContext;	/* short-term context for comparisons */
+	ExprState   *eqfunction;		/* tuple equality qual */
 } UniqueState;
 
 /* ----------------
@@ -2079,11 +2082,11 @@ typedef struct SetOpStatePerGroupData *SetOpStatePerGroup;
 typedef struct SetOpState
 {
 	PlanState	ps;				/* its first field is NodeTag */
-	FmgrInfo   *eqfunctions;	/* per-grouping-field equality fns */
+	ExprState  *eqfunction;		/* equality comparator */
+	Oid		   *eqfuncoids;		/* per-grouping-field equality fns */
 	FmgrInfo   *hashfunctions;	/* per-grouping-field hash fns */
 	bool		setop_done;		/* indicates completion of output scan */
 	long		numOutput;		/* number of dups left to output */
-	MemoryContext tempContext;	/* short-term context for comparisons */
 	/* these fields are used in SETOP_SORTED mode: */
 	SetOpStatePerGroup pergroup;	/* per-group working state */
 	HeapTuple	grp_firstTuple; /* copy of first tuple of current group */