Convert SetOp to read its inputs as outerPlan and innerPlan.

The original design for set operations involved appending the two
input relations into one and adding a flag column that allows
distinguishing which side each row came from.  Then the SetOp node
pries them apart again based on the flag.  This is bizarre.  The
only apparent reason to do it is that when sorting, we'd only need
one Sort node not two.  But since sorting is at least O(N log N),
sorting all the data is actually worse than sorting each side
separately --- plus, we have no chance of taking advantage of
presorted input.  On top of that, adding the flag column frequently
requires an additional projection step that adds cycles, and then
the Append node isn't free either.  Let's get rid of all of that
and make the SetOp node have two separate children, using the
existing outerPlan/innerPlan infrastructure.

This initial patch re-implements nodeSetop.c and does a bare minimum
of work on the planner side to generate correctly-shaped plans.
In particular, I've tried not to change the cost estimates here,
so that the visible changes in the regression test results will only
involve removal of useless projection steps and not any changes in
whether to use sorted vs hashed mode.

For SORTED mode, we combine successive identical tuples from each
input into groups, and then merge-join the groups.  The tuple
comparisons now use SortSupport instead of simple equality, but
the group-formation part should involve roughly the same number of
tuple comparisons as before.  The cross-comparisons between left and
right groups probably add to that, but I'm not sure to quantify how
many more comparisons we might need.

For HASHED mode, nodeSetop's logic is almost the same as before,
just refactored into two separate loops instead of one loop that
has an assumption that it will see all the left-hand inputs first.

In both modes, I added early-exit logic to not bother reading the
right-hand relation if the left-hand input is empty, since neither
INTERSECT nor EXCEPT modes can produce any output if the left input
is empty.  This could have been done before in the hashed mode, but
not in sorted mode.  Sorted mode can also stop as soon as it exhausts
the left input; any remaining right-hand tuples cannot have matches.

Also, this patch adds some infrastructure for detecting whether
child plan nodes all output the same type of tuple table slot.
If they do, the hash table logic can use slightly more efficient
code based on assuming that that's the input slot type it will see.
We'll make use of that infrastructure in other plan node types later.

Patch by me; thanks to Richard Guo and David Rowley for review.

Discussion: https://postgr.es/m/1850138.1731549611@sss.pgh.pa.us

1 files changed, 311 insertions, 226 deletions

diff --git a/src/backend/executor/nodeSetOp.c b/src/backend/executor/nodeSetOp.c
index b40d81f3ffa..09089204e8b 100644
--- a/src/backend/executor/nodeSetOp.c
+++ b/src/backend/executor/nodeSetOp.c
@@ -3,29 +3,30 @@
  * nodeSetOp.c
  *	  Routines to handle INTERSECT and EXCEPT selection
  *
- * The input of a SetOp node consists of tuples from two relations,
- * which have been combined into one dataset, with a junk attribute added
- * that shows which relation each tuple came from.  In SETOP_SORTED mode,
- * the input has furthermore been sorted according to all the grouping
- * columns (ie, all the non-junk attributes).  The SetOp node scans each
- * group of identical tuples to determine how many came from each input
- * relation.  Then it is a simple matter to emit the output demanded by the
- * SQL spec for INTERSECT, INTERSECT ALL, EXCEPT, or EXCEPT ALL.
+ * The input of a SetOp node consists of two relations (outer and inner)
+ * with identical column sets.  In EXCEPT queries the outer relation is
+ * always the left side, while in INTERSECT cases the planner tries to
+ * make the outer relation be the smaller of the two inputs.
  *
- * In SETOP_HASHED mode, the input is delivered in no particular order,
- * except that we know all the tuples from one input relation will come before
- * all the tuples of the other.  The planner guarantees that the first input
- * relation is the left-hand one for EXCEPT, and tries to make the smaller
- * input relation come first for INTERSECT.  We build a hash table in memory
- * with one entry for each group of identical tuples, and count the number of
- * tuples in the group from each relation.  After seeing all the input, we
- * scan the hashtable and generate the correct output using those counts.
- * We can avoid making hashtable entries for any tuples appearing only in the
- * second input relation, since they cannot result in any output.
+ * In SETOP_SORTED mode, each input has been sorted according to all the
+ * grouping columns.  The SetOp node essentially performs a merge join on
+ * the grouping columns, except that it is only interested in counting how
+ * many tuples from each input match.  Then it is a simple matter to emit
+ * the output demanded by the SQL spec for INTERSECT, INTERSECT ALL, EXCEPT,
+ * or EXCEPT ALL.
+ *
+ * In SETOP_HASHED mode, the inputs are delivered in no particular order.
+ * We read the outer relation and build a hash table in memory with one entry
+ * for each group of identical tuples, counting the number of tuples in the
+ * group.  Then we read the inner relation and count the number of tuples
+ * matching each outer group.  (We can disregard any tuples appearing only
+ * in the inner relation, since they cannot result in any output.)  After
+ * seeing all the input, we scan the hashtable and generate the correct
+ * output using those counts.
  *
  * This node type is not used for UNION or UNION ALL, since those can be
- * implemented more cheaply (there's no need for the junk attribute to
- * identify the source relation).
+ * implemented more cheaply (there's no need to count the number of
+ * matching tuples).
  *
  * Note that SetOp does no qual checking nor projection.  The delivered
  * output tuples are just copies of the first-to-arrive tuple in each
@@ -54,66 +55,29 @@
 /*
  * SetOpStatePerGroupData - per-group working state
  *
- * These values are working state that is initialized at the start of
- * an input tuple group and updated for each input tuple.
- *
- * In SETOP_SORTED mode, we need only one of these structs, and it's kept in
- * the plan state node.  In SETOP_HASHED mode, the hash table contains one
- * of these for each tuple group.
+ * In SETOP_SORTED mode, we need only one of these structs, and it's just a
+ * local in setop_retrieve_sorted.  In SETOP_HASHED mode, the hash table
+ * contains one of these for each tuple group.
  */
 typedef struct SetOpStatePerGroupData
 {
-	long		numLeft;		/* number of left-input dups in group */
-	long		numRight;		/* number of right-input dups in group */
-}			SetOpStatePerGroupData;
+	int64		numLeft;		/* number of left-input dups in group */
+	int64		numRight;		/* number of right-input dups in group */
+} SetOpStatePerGroupData;
+
+typedef SetOpStatePerGroupData *SetOpStatePerGroup;
 
 
-static TupleTableSlot *setop_retrieve_direct(SetOpState *setopstate);
+static TupleTableSlot *setop_retrieve_sorted(SetOpState *setopstate);
+static void setop_load_group(SetOpStatePerInput *input, PlanState *inputPlan,
+							 SetOpState *setopstate);
+static int	setop_compare_slots(TupleTableSlot *s1, TupleTableSlot *s2,
+								SetOpState *setopstate);
 static void setop_fill_hash_table(SetOpState *setopstate);
 static TupleTableSlot *setop_retrieve_hash_table(SetOpState *setopstate);
 
 
 /*
- * Initialize state for a new group of input values.
- */
-static inline void
-initialize_counts(SetOpStatePerGroup pergroup)
-{
-	pergroup->numLeft = pergroup->numRight = 0;
-}
-
-/*
- * Advance the appropriate counter for one input tuple.
- */
-static inline void
-advance_counts(SetOpStatePerGroup pergroup, int flag)
-{
-	if (flag)
-		pergroup->numRight++;
-	else
-		pergroup->numLeft++;
-}
-
-/*
- * Fetch the "flag" column from an input tuple.
- * This is an integer column with value 0 for left side, 1 for right side.
- */
-static int
-fetch_tuple_flag(SetOpState *setopstate, TupleTableSlot *inputslot)
-{
-	SetOp	   *node = (SetOp *) setopstate->ps.plan;
-	int			flag;
-	bool		isNull;
-
-	flag = DatumGetInt32(slot_getattr(inputslot,
-									  node->flagColIdx,
-									  &isNull));
-	Assert(!isNull);
-	Assert(flag == 0 || flag == 1);
-	return flag;
-}
-
-/*
  * Initialize the hash table to empty.
  */
 static void
@@ -126,14 +90,19 @@ build_hash_table(SetOpState *setopstate)
 	Assert(node->strategy == SETOP_HASHED);
 	Assert(node->numGroups > 0);
 
+	/*
+	 * If both child plans deliver the same fixed tuple slot type, we can tell
+	 * BuildTupleHashTableExt to expect that slot type as input.  Otherwise,
+	 * we'll pass NULL denoting that any slot type is possible.
+	 */
 	setopstate->hashtable = BuildTupleHashTableExt(&setopstate->ps,
 												   desc,
-												   NULL,
+												   ExecGetCommonChildSlotOps(&setopstate->ps),
 												   node->numCols,
-												   node->dupColIdx,
+												   node->cmpColIdx,
 												   setopstate->eqfuncoids,
 												   setopstate->hashfunctions,
-												   node->dupCollations,
+												   node->cmpCollations,
 												   node->numGroups,
 												   0,
 												   setopstate->ps.state->es_query_cxt,
@@ -218,108 +187,126 @@ ExecSetOp(PlanState *pstate)
 		return setop_retrieve_hash_table(node);
 	}
 	else
-		return setop_retrieve_direct(node);
+		return setop_retrieve_sorted(node);
 }
 
 /*
  * ExecSetOp for non-hashed case
  */
 static TupleTableSlot *
-setop_retrieve_direct(SetOpState *setopstate)
+setop_retrieve_sorted(SetOpState *setopstate)
 {
 	PlanState  *outerPlan;
-	SetOpStatePerGroup pergroup;
-	TupleTableSlot *outerslot;
+	PlanState  *innerPlan;
 	TupleTableSlot *resultTupleSlot;
-	ExprContext *econtext = setopstate->ps.ps_ExprContext;
 
 	/*
 	 * get state info from node
 	 */
 	outerPlan = outerPlanState(setopstate);
-	pergroup = (SetOpStatePerGroup) setopstate->pergroup;
+	innerPlan = innerPlanState(setopstate);
 	resultTupleSlot = setopstate->ps.ps_ResultTupleSlot;
 
 	/*
-	 * We loop retrieving groups until we find one we should return
+	 * If first time through, establish the invariant that setop_load_group
+	 * expects: each side's nextTupleSlot is the next output from the child
+	 * plan, or empty if there is no more output from it.
 	 */
-	while (!setopstate->setop_done)
+	if (setopstate->need_init)
 	{
+		setopstate->need_init = false;
+
+		setopstate->leftInput.nextTupleSlot = ExecProcNode(outerPlan);
+
 		/*
-		 * If we don't already have the first tuple of the new group, fetch it
-		 * from the outer plan.
+		 * If the outer relation is empty, then we will emit nothing, and we
+		 * don't need to read the inner relation at all.
 		 */
-		if (setopstate->grp_firstTuple == NULL)
+		if (TupIsNull(setopstate->leftInput.nextTupleSlot))
 		{
-			outerslot = ExecProcNode(outerPlan);
-			if (!TupIsNull(outerslot))
-			{
-				/* Make a copy of the first input tuple */
-				setopstate->grp_firstTuple = ExecCopySlotHeapTuple(outerslot);
-			}
-			else
-			{
-				/* outer plan produced no tuples at all */
-				setopstate->setop_done = true;
-				return NULL;
-			}
+			setopstate->setop_done = true;
+			return NULL;
 		}
 
+		setopstate->rightInput.nextTupleSlot = ExecProcNode(innerPlan);
+
+		/* Set flags that we've not completed either side's group */
+		setopstate->leftInput.needGroup = true;
+		setopstate->rightInput.needGroup = true;
+	}
+
+	/*
+	 * We loop retrieving groups until we find one we should return
+	 */
+	while (!setopstate->setop_done)
+	{
+		int			cmpresult;
+		SetOpStatePerGroupData pergroup;
+
 		/*
-		 * Store the copied first input tuple in the tuple table slot reserved
-		 * for it.  The tuple will be deleted when it is cleared from the
-		 * slot.
+		 * Fetch the rest of the current outer group, if we didn't already.
 		 */
-		ExecStoreHeapTuple(setopstate->grp_firstTuple,
-						   resultTupleSlot,
-						   true);
-		setopstate->grp_firstTuple = NULL;	/* don't keep two pointers */
+		if (setopstate->leftInput.needGroup)
+			setop_load_group(&setopstate->leftInput, outerPlan, setopstate);
 
-		/* Initialize working state for a new input tuple group */
-		initialize_counts(pergroup);
+		/*
+		 * If no more outer groups, we're done, and don't need to look at any
+		 * more of the inner relation.
+		 */
+		if (setopstate->leftInput.numTuples == 0)
+		{
+			setopstate->setop_done = true;
+			break;
+		}
 
-		/* Count the first input tuple */
-		advance_counts(pergroup,
-					   fetch_tuple_flag(setopstate, resultTupleSlot));
+		/*
+		 * Fetch the rest of the current inner group, if we didn't already.
+		 */
+		if (setopstate->rightInput.needGroup)
+			setop_load_group(&setopstate->rightInput, innerPlan, setopstate);
 
 		/*
-		 * Scan the outer plan until we exhaust it or cross a group boundary.
+		 * Determine whether we have matching groups on both sides (this is
+		 * basically like the core logic of a merge join).
 		 */
-		for (;;)
-		{
-			outerslot = ExecProcNode(outerPlan);
-			if (TupIsNull(outerslot))
-			{
-				/* no more outer-plan tuples available */
-				setopstate->setop_done = true;
-				break;
-			}
-
-			/*
-			 * Check whether we've crossed a group boundary.
-			 */
-			econtext->ecxt_outertuple = resultTupleSlot;
-			econtext->ecxt_innertuple = outerslot;
-
-			if (!ExecQualAndReset(setopstate->eqfunction, econtext))
-			{
-				/*
-				 * Save the first input tuple of the next group.
-				 */
-				setopstate->grp_firstTuple = ExecCopySlotHeapTuple(outerslot);
-				break;
-			}
+		if (setopstate->rightInput.numTuples == 0)
+			cmpresult = -1;		/* as though left input is lesser */
+		else
+			cmpresult = setop_compare_slots(setopstate->leftInput.firstTupleSlot,
+											setopstate->rightInput.firstTupleSlot,
+											setopstate);
 
-			/* Still in same group, so count this tuple */
-			advance_counts(pergroup,
-						   fetch_tuple_flag(setopstate, outerslot));
+		if (cmpresult < 0)
+		{
+			/* Left group is first, and has no right matches */
+			pergroup.numLeft = setopstate->leftInput.numTuples;
+			pergroup.numRight = 0;
+			/* We'll need another left group next time */
+			setopstate->leftInput.needGroup = true;
+		}
+		else if (cmpresult == 0)
+		{
+			/* We have matching groups */
+			pergroup.numLeft = setopstate->leftInput.numTuples;
+			pergroup.numRight = setopstate->rightInput.numTuples;
+			/* We'll need to read from both sides next time */
+			setopstate->leftInput.needGroup = true;
+			setopstate->rightInput.needGroup = true;
+		}
+		else
+		{
+			/* Right group has no left matches, so we can ignore it */
+			setopstate->rightInput.needGroup = true;
+			continue;
 		}
 
 		/*
-		 * Done scanning input tuple group.  See if we should emit any copies
-		 * of result tuple, and if so return the first copy.
+		 * Done scanning these input tuple groups.  See if we should emit any
+		 * copies of result tuple, and if so return the first copy.  (Note
+		 * that the result tuple is the same as the left input's firstTuple
+		 * slot.)
 		 */
-		set_output_count(setopstate, pergroup);
+		set_output_count(setopstate, &pergroup);
 
 		if (setopstate->numOutput > 0)
 		{
@@ -334,84 +321,168 @@ setop_retrieve_direct(SetOpState *setopstate)
 }
 
 /*
- * ExecSetOp for hashed case: phase 1, read input and build hash table
+ * Load next group of tuples from one child plan or the other.
+ *
+ * On entry, we've already read the first tuple of the next group
+ * (if there is one) into input->nextTupleSlot.  This invariant
+ * is maintained on exit.
+ */
+static void
+setop_load_group(SetOpStatePerInput *input, PlanState *inputPlan,
+				 SetOpState *setopstate)
+{
+	input->needGroup = false;
+
+	/* If we've exhausted this child plan, report an empty group */
+	if (TupIsNull(input->nextTupleSlot))
+	{
+		ExecClearTuple(input->firstTupleSlot);
+		input->numTuples = 0;
+		return;
+	}
+
+	/* Make a local copy of the first tuple for comparisons */
+	ExecStoreMinimalTuple(ExecCopySlotMinimalTuple(input->nextTupleSlot),
+						  input->firstTupleSlot,
+						  true);
+	/* and count it */
+	input->numTuples = 1;
+
+	/* Scan till we find the end-of-group */
+	for (;;)
+	{
+		int			cmpresult;
+
+		/* Get next input tuple, if there is one */
+		input->nextTupleSlot = ExecProcNode(inputPlan);
+		if (TupIsNull(input->nextTupleSlot))
+			break;
+
+		/* There is; does it belong to same group as firstTuple? */
+		cmpresult = setop_compare_slots(input->firstTupleSlot,
+										input->nextTupleSlot,
+										setopstate);
+		Assert(cmpresult <= 0); /* else input is mis-sorted */
+		if (cmpresult != 0)
+			break;
+
+		/* Still in same group, so count this tuple */
+		input->numTuples++;
+	}
+}
+
+/*
+ * Compare the tuples in the two given slots.
+ */
+static int
+setop_compare_slots(TupleTableSlot *s1, TupleTableSlot *s2,
+					SetOpState *setopstate)
+{
+	/* We'll often need to fetch all the columns, so just do it */
+	slot_getallattrs(s1);
+	slot_getallattrs(s2);
+	for (int nkey = 0; nkey < setopstate->numCols; nkey++)
+	{
+		SortSupport sortKey = setopstate->sortKeys + nkey;
+		AttrNumber	attno = sortKey->ssup_attno;
+		Datum		datum1 = s1->tts_values[attno - 1],
+					datum2 = s2->tts_values[attno - 1];
+		bool		isNull1 = s1->tts_isnull[attno - 1],
+					isNull2 = s2->tts_isnull[attno - 1];
+		int			compare;
+
+		compare = ApplySortComparator(datum1, isNull1,
+									  datum2, isNull2,
+									  sortKey);
+		if (compare != 0)
+			return compare;
+	}
+	return 0;
+}
+
+/*
+ * ExecSetOp for hashed case: phase 1, read inputs and build hash table
  */
 static void
 setop_fill_hash_table(SetOpState *setopstate)
 {
-	SetOp	   *node = (SetOp *) setopstate->ps.plan;
 	PlanState  *outerPlan;
-	int			firstFlag;
-	bool		in_first_rel PG_USED_FOR_ASSERTS_ONLY;
+	PlanState  *innerPlan;
 	ExprContext *econtext = setopstate->ps.ps_ExprContext;
+	bool		have_tuples = false;
 
 	/*
 	 * get state info from node
 	 */
 	outerPlan = outerPlanState(setopstate);
-	firstFlag = node->firstFlag;
-	/* verify planner didn't mess up */
-	Assert(firstFlag == 0 ||
-		   (firstFlag == 1 &&
-			(node->cmd == SETOPCMD_INTERSECT ||
-			 node->cmd == SETOPCMD_INTERSECT_ALL)));
+	innerPlan = innerPlanState(setopstate);
 
 	/*
 	 * Process each outer-plan tuple, and then fetch the next one, until we
 	 * exhaust the outer plan.
 	 */
-	in_first_rel = true;
 	for (;;)
 	{
 		TupleTableSlot *outerslot;
-		int			flag;
 		TupleHashEntryData *entry;
 		bool		isnew;
 
 		outerslot = ExecProcNode(outerPlan);
 		if (TupIsNull(outerslot))
 			break;
+		have_tuples = true;
 
-		/* Identify whether it's left or right input */
-		flag = fetch_tuple_flag(setopstate, outerslot);
+		/* Find or build hashtable entry for this tuple's group */
+		entry = LookupTupleHashEntry(setopstate->hashtable,
+									 outerslot,
+									 &isnew, NULL);
 
-		if (flag == firstFlag)
+		/* If new tuple group, initialize counts to zero */
+		if (isnew)
 		{
-			/* (still) in first input relation */
-			Assert(in_first_rel);
-
-			/* Find or build hashtable entry for this tuple's group */
-			entry = LookupTupleHashEntry(setopstate->hashtable, outerslot,
-										 &isnew, NULL);
-
-			/* If new tuple group, initialize counts */
-			if (isnew)
-			{
-				entry->additional = (SetOpStatePerGroup)
-					MemoryContextAlloc(setopstate->hashtable->tablecxt,
+			entry->additional = (SetOpStatePerGroup)
+				MemoryContextAllocZero(setopstate->hashtable->tablecxt,
 									   sizeof(SetOpStatePerGroupData));
-				initialize_counts((SetOpStatePerGroup) entry->additional);
-			}
-
-			/* Advance the counts */
-			advance_counts((SetOpStatePerGroup) entry->additional, flag);
 		}
-		else
+
+		/* Advance the counts */
+		((SetOpStatePerGroup) entry->additional)->numLeft++;
+
+		/* Must reset expression context after each hashtable lookup */
+		ResetExprContext(econtext);
+	}
+
+	/*
+	 * If the outer relation is empty, then we will emit nothing, and we don't
+	 * need to read the inner relation at all.
+	 */
+	if (have_tuples)
+	{
+		/*
+		 * Process each inner-plan tuple, and then fetch the next one, until
+		 * we exhaust the inner plan.
+		 */
+		for (;;)
 		{
-			/* reached second relation */
-			in_first_rel = false;
+			TupleTableSlot *innerslot;
+			TupleHashEntryData *entry;
+
+			innerslot = ExecProcNode(innerPlan);
+			if (TupIsNull(innerslot))
+				break;
 
 			/* For tuples not seen previously, do not make hashtable entry */
-			entry = LookupTupleHashEntry(setopstate->hashtable, outerslot,
+			entry = LookupTupleHashEntry(setopstate->hashtable,
+										 innerslot,
 										 NULL, NULL);
 
 			/* Advance the counts if entry is already present */
 			if (entry)
-				advance_counts((SetOpStatePerGroup) entry->additional, flag);
-		}
+				((SetOpStatePerGroup) entry->additional)->numRight++;
 
-		/* Must reset expression context after each hashtable lookup */
-		ResetExprContext(econtext);
+			/* Must reset expression context after each hashtable lookup */
+			ResetExprContext(econtext);
+		}
 	}
 
 	setopstate->table_filled = true;
@@ -482,7 +553,6 @@ SetOpState *
 ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 {
 	SetOpState *setopstate;
-	TupleDesc	outerDesc;
 
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -495,14 +565,10 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	setopstate->ps.state = estate;
 	setopstate->ps.ExecProcNode = ExecSetOp;
 
-	setopstate->eqfuncoids = NULL;
-	setopstate->hashfunctions = NULL;
 	setopstate->setop_done = false;
 	setopstate->numOutput = 0;
-	setopstate->pergroup = NULL;
-	setopstate->grp_firstTuple = NULL;
-	setopstate->hashtable = NULL;
-	setopstate->tableContext = NULL;
+	setopstate->numCols = node->numCols;
+	setopstate->need_init = true;
 
 	/*
 	 * create expression context
@@ -523,52 +589,72 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 	/*
 	 * initialize child nodes
 	 *
-	 * If we are hashing then the child plan does not need to handle REWIND
+	 * If we are hashing then the child plans do not need to handle REWIND
 	 * efficiently; see ExecReScanSetOp.
 	 */
 	if (node->strategy == SETOP_HASHED)
 		eflags &= ~EXEC_FLAG_REWIND;
 	outerPlanState(setopstate) = ExecInitNode(outerPlan(node), estate, eflags);
-	outerDesc = ExecGetResultType(outerPlanState(setopstate));
+	innerPlanState(setopstate) = ExecInitNode(innerPlan(node), estate, eflags);
 
 	/*
-	 * Initialize result slot and type. Setop nodes do no projections, so
-	 * initialize projection info for this node appropriately.
+	 * Initialize locally-allocated slots.  In hashed mode, we just need a
+	 * result slot.  In sorted mode, we need one first-tuple-of-group slot for
+	 * each input; we use the result slot for the left input's slot and create
+	 * another for the right input.  (Note: the nextTupleSlot slots are not
+	 * ours, but just point to the last slot returned by the input plan node.)
 	 */
-	ExecInitResultTupleSlotTL(&setopstate->ps,
-							  node->strategy == SETOP_HASHED ?
-							  &TTSOpsMinimalTuple : &TTSOpsHeapTuple);
+	ExecInitResultTupleSlotTL(&setopstate->ps, &TTSOpsMinimalTuple);
+	if (node->strategy != SETOP_HASHED)
+	{
+		setopstate->leftInput.firstTupleSlot =
+			setopstate->ps.ps_ResultTupleSlot;
+		setopstate->rightInput.firstTupleSlot =
+			ExecInitExtraTupleSlot(estate,
+								   setopstate->ps.ps_ResultTupleDesc,
+								   &TTSOpsMinimalTuple);
+	}
+
+	/* Setop nodes do no projections. */
 	setopstate->ps.ps_ProjInfo = NULL;
 
 	/*
-	 * Precompute fmgr lookup data for inner loop. We need both equality and
-	 * hashing functions to do it by hashing, but only equality if not
-	 * hashing.
+	 * Precompute fmgr lookup data for inner loop.  We need equality and
+	 * hashing functions to do it by hashing, while for sorting we need
+	 * SortSupport data.
 	 */
 	if (node->strategy == SETOP_HASHED)
 		execTuplesHashPrepare(node->numCols,
-							  node->dupOperators,
+							  node->cmpOperators,
 							  &setopstate->eqfuncoids,
 							  &setopstate->hashfunctions);
 	else
-		setopstate->eqfunction =
-			execTuplesMatchPrepare(outerDesc,
-								   node->numCols,
-								   node->dupColIdx,
-								   node->dupOperators,
-								   node->dupCollations,
-								   &setopstate->ps);
+	{
+		int			nkeys = node->numCols;
+
+		setopstate->sortKeys = (SortSupport)
+			palloc0(nkeys * sizeof(SortSupportData));
+		for (int i = 0; i < nkeys; i++)
+		{
+			SortSupport sortKey = setopstate->sortKeys + i;
+
+			sortKey->ssup_cxt = CurrentMemoryContext;
+			sortKey->ssup_collation = node->cmpCollations[i];
+			sortKey->ssup_nulls_first = node->cmpNullsFirst[i];
+			sortKey->ssup_attno = node->cmpColIdx[i];
+			/* abbreviated key conversion is not useful here */
+			sortKey->abbreviate = false;
 
+			PrepareSortSupportFromOrderingOp(node->cmpOperators[i], sortKey);
+		}
+	}
+
+	/* Create a hash table if needed */
 	if (node->strategy == SETOP_HASHED)
 	{
 		build_hash_table(setopstate);
 		setopstate->table_filled = false;
 	}
-	else
-	{
-		setopstate->pergroup =
-			(SetOpStatePerGroup) palloc0(sizeof(SetOpStatePerGroupData));
-	}
 
 	return setopstate;
 }
@@ -576,7 +662,7 @@ ExecInitSetOp(SetOp *node, EState *estate, int eflags)
 /* ----------------------------------------------------------------
  *		ExecEndSetOp
  *
- *		This shuts down the subplan and frees resources allocated
+ *		This shuts down the subplans and frees resources allocated
  *		to this node.
  * ----------------------------------------------------------------
  */
@@ -588,6 +674,7 @@ ExecEndSetOp(SetOpState *node)
 		MemoryContextDelete(node->tableContext);
 
 	ExecEndNode(outerPlanState(node));
+	ExecEndNode(innerPlanState(node));
 }
 
 
@@ -595,6 +682,7 @@ void
 ExecReScanSetOp(SetOpState *node)
 {
 	PlanState  *outerPlan = outerPlanState(node);
+	PlanState  *innerPlan = innerPlanState(node);
 
 	ExecClearTuple(node->ps.ps_ResultTupleSlot);
 	node->setop_done = false;
@@ -612,34 +700,29 @@ ExecReScanSetOp(SetOpState *node)
 			return;
 
 		/*
-		 * If we do have the hash table and the subplan does not have any
+		 * If we do have the hash table and the subplans do not have any
 		 * parameter changes, then we can just rescan the existing hash table;
 		 * no need to build it again.
 		 */
-		if (outerPlan->chgParam == NULL)
+		if (outerPlan->chgParam == NULL && innerPlan->chgParam == NULL)
 		{
 			ResetTupleHashIterator(node->hashtable, &node->hashiter);
 			return;
 		}
-	}
-
-	/* Release first tuple of group, if we have made a copy */
-	if (node->grp_firstTuple != NULL)
-	{
-		heap_freetuple(node->grp_firstTuple);
-		node->grp_firstTuple = NULL;
-	}
 
-	/* Release any hashtable storage */
-	if (node->tableContext)
-		MemoryContextReset(node->tableContext);
+		/* Release any hashtable storage */
+		if (node->tableContext)
+			MemoryContextReset(node->tableContext);
 
-	/* And rebuild empty hashtable if needed */
-	if (((SetOp *) node->ps.plan)->strategy == SETOP_HASHED)
-	{
+		/* And rebuild an empty hashtable */
 		ResetTupleHashTable(node->hashtable);
 		node->table_filled = false;
 	}
+	else
+	{
+		/* Need to re-read first input from each side */
+		node->need_init = true;
+	}
 
 	/*
 	 * if chgParam of subnode is not null then plan will be re-scanned by
@@ -647,4 +730,6 @@ ExecReScanSetOp(SetOpState *node)
 	 */
 	if (outerPlan->chgParam == NULL)
 		ExecReScan(outerPlan);
+	if (innerPlan->chgParam == NULL)
+		ExecReScan(innerPlan);
 }