Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 6862 insertions, 0 deletions

diff --git a/src/backend/optimizer/prep/Makefile b/src/backend/optimizer/prep/Makefile
new file mode 100644
index 0000000..6f8c6c8
--- /dev/null
+++ b/src/backend/optimizer/prep/Makefile
@@ -0,0 +1,22 @@
+#-------------------------------------------------------------------------
+#
+# Makefile--
+#    Makefile for optimizer/prep
+#
+# IDENTIFICATION
+#    src/backend/optimizer/prep/Makefile
+#
+#-------------------------------------------------------------------------
+
+subdir = src/backend/optimizer/prep
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+
+OBJS = \
+	prepagg.o \
+	prepjointree.o \
+	prepqual.o \
+	preptlist.o \
+	prepunion.o
+
+include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/optimizer/prep/prepagg.c b/src/backend/optimizer/prep/prepagg.c
new file mode 100644
index 0000000..e1c5257
--- /dev/null
+++ b/src/backend/optimizer/prep/prepagg.c
@@ -0,0 +1,674 @@
+/*-------------------------------------------------------------------------
+ *
+ * prepagg.c
+ *	  Routines to preprocess aggregate function calls
+ *
+ * If there are identical aggregate calls in the query, they only need to
+ * be computed once.  Also, some aggregate functions can share the same
+ * transition state, so that we only need to call the final function for
+ * them separately.  These optimizations are independent of how the
+ * aggregates are executed.
+ *
+ * preprocess_aggrefs() detects those cases, creates AggInfo and
+ * AggTransInfo structs for each aggregate and transition state that needs
+ * to be computed, and sets the 'aggno' and 'transno' fields in the Aggrefs
+ * accordingly.  It also resolves polymorphic transition types, and sets
+ * the 'aggtranstype' fields accordingly.
+ *
+ * XXX: The AggInfo and AggTransInfo structs are thrown away after
+ * planning, so executor startup has to perform some of the same lookups
+ * of transition functions and initial values that we do here.  One day, we
+ * might want to carry that information to the Agg nodes to save the effort
+ * at executor startup.  The Agg nodes are constructed much later in the
+ * planning, however, so it's not trivial.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/prep/prepagg.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "catalog/pg_aggregate.h"
+#include "catalog/pg_type.h"
+#include "nodes/nodeFuncs.h"
+#include "nodes/pathnodes.h"
+#include "optimizer/clauses.h"
+#include "optimizer/cost.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/plancat.h"
+#include "optimizer/prep.h"
+#include "parser/parse_agg.h"
+#include "utils/builtins.h"
+#include "utils/datum.h"
+#include "utils/fmgroids.h"
+#include "utils/lsyscache.h"
+#include "utils/memutils.h"
+#include "utils/syscache.h"
+
+static bool preprocess_aggrefs_walker(Node *node, PlannerInfo *root);
+static int	find_compatible_agg(PlannerInfo *root, Aggref *newagg,
+								List **same_input_transnos);
+static int	find_compatible_trans(PlannerInfo *root, Aggref *newagg,
+								  bool shareable,
+								  Oid aggtransfn, Oid aggtranstype,
+								  int transtypeLen, bool transtypeByVal,
+								  Oid aggcombinefn,
+								  Oid aggserialfn, Oid aggdeserialfn,
+								  Datum initValue, bool initValueIsNull,
+								  List *transnos);
+static Datum GetAggInitVal(Datum textInitVal, Oid transtype);
+
+/* -----------------
+ * Resolve the transition type of all Aggrefs, and determine which Aggrefs
+ * can share aggregate or transition state.
+ *
+ * Information about the aggregates and transition functions are collected
+ * in the root->agginfos and root->aggtransinfos lists.  The 'aggtranstype',
+ * 'aggno', and 'aggtransno' fields of each Aggref are filled in.
+ *
+ * NOTE: This modifies the Aggrefs in the input expression in-place!
+ *
+ * We try to optimize by detecting duplicate aggregate functions so that
+ * their state and final values are re-used, rather than needlessly being
+ * re-calculated independently.  We also detect aggregates that are not
+ * the same, but which can share the same transition state.
+ *
+ * Scenarios:
+ *
+ * 1. Identical aggregate function calls appear in the query:
+ *
+ *	  SELECT SUM(x) FROM ... HAVING SUM(x) > 0
+ *
+ *	  Since these aggregates are identical, we only need to calculate
+ *	  the value once.  Both aggregates will share the same 'aggno' value.
+ *
+ * 2. Two different aggregate functions appear in the query, but the
+ *	  aggregates have the same arguments, transition functions and
+ *	  initial values (and, presumably, different final functions):
+ *
+ *	  SELECT AVG(x), STDDEV(x) FROM ...
+ *
+ *	  In this case we must create a new AggInfo for the varying aggregate,
+ *	  and we need to call the final functions separately, but we need
+ *	  only run the transition function once.  (This requires that the
+ *	  final functions be nondestructive of the transition state, but
+ *	  that's required anyway for other reasons.)
+ *
+ * For either of these optimizations to be valid, all aggregate properties
+ * used in the transition phase must be the same, including any modifiers
+ * such as ORDER BY, DISTINCT and FILTER, and the arguments mustn't
+ * contain any volatile functions.
+ * -----------------
+ */
+void
+preprocess_aggrefs(PlannerInfo *root, Node *clause)
+{
+	(void) preprocess_aggrefs_walker(clause, root);
+}
+
+static void
+preprocess_aggref(Aggref *aggref, PlannerInfo *root)
+{
+	HeapTuple	aggTuple;
+	Form_pg_aggregate aggform;
+	Oid			aggtransfn;
+	Oid			aggfinalfn;
+	Oid			aggcombinefn;
+	Oid			aggserialfn;
+	Oid			aggdeserialfn;
+	Oid			aggtranstype;
+	int32		aggtranstypmod;
+	int32		aggtransspace;
+	bool		shareable;
+	int			aggno;
+	int			transno;
+	List	   *same_input_transnos;
+	int16		resulttypeLen;
+	bool		resulttypeByVal;
+	Datum		textInitVal;
+	Datum		initValue;
+	bool		initValueIsNull;
+	bool		transtypeByVal;
+	int16		transtypeLen;
+	Oid			inputTypes[FUNC_MAX_ARGS];
+	int			numArguments;
+
+	Assert(aggref->agglevelsup == 0);
+
+	/*
+	 * Fetch info about the aggregate from pg_aggregate.  Note it's correct to
+	 * ignore the moving-aggregate variant, since what we're concerned with
+	 * here is aggregates not window functions.
+	 */
+	aggTuple = SearchSysCache1(AGGFNOID,
+							   ObjectIdGetDatum(aggref->aggfnoid));
+	if (!HeapTupleIsValid(aggTuple))
+		elog(ERROR, "cache lookup failed for aggregate %u",
+			 aggref->aggfnoid);
+	aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
+	aggtransfn = aggform->aggtransfn;
+	aggfinalfn = aggform->aggfinalfn;
+	aggcombinefn = aggform->aggcombinefn;
+	aggserialfn = aggform->aggserialfn;
+	aggdeserialfn = aggform->aggdeserialfn;
+	aggtranstype = aggform->aggtranstype;
+	aggtransspace = aggform->aggtransspace;
+
+	/*
+	 * Resolve the possibly-polymorphic aggregate transition type.
+	 */
+
+	/* extract argument types (ignoring any ORDER BY expressions) */
+	numArguments = get_aggregate_argtypes(aggref, inputTypes);
+
+	/* resolve actual type of transition state, if polymorphic */
+	aggtranstype = resolve_aggregate_transtype(aggref->aggfnoid,
+											   aggtranstype,
+											   inputTypes,
+											   numArguments);
+	aggref->aggtranstype = aggtranstype;
+
+	/*
+	 * If transition state is of same type as first aggregated input, assume
+	 * it's the same typmod (same width) as well.  This works for cases like
+	 * MAX/MIN and is probably somewhat reasonable otherwise.
+	 */
+	aggtranstypmod = -1;
+	if (aggref->args)
+	{
+		TargetEntry *tle = (TargetEntry *) linitial(aggref->args);
+
+		if (aggtranstype == exprType((Node *) tle->expr))
+			aggtranstypmod = exprTypmod((Node *) tle->expr);
+	}
+
+	/*
+	 * If finalfn is marked read-write, we can't share transition states; but
+	 * it is okay to share states for AGGMODIFY_SHAREABLE aggs.
+	 *
+	 * In principle, in a partial aggregate, we could share the transition
+	 * state even if the final function is marked as read-write, because the
+	 * partial aggregate doesn't execute the final function.  But it's too
+	 * early to know whether we're going perform a partial aggregate.
+	 */
+	shareable = (aggform->aggfinalmodify != AGGMODIFY_READ_WRITE);
+
+	/* get info about the output value's datatype */
+	get_typlenbyval(aggref->aggtype,
+					&resulttypeLen,
+					&resulttypeByVal);
+
+	/* get initial value */
+	textInitVal = SysCacheGetAttr(AGGFNOID, aggTuple,
+								  Anum_pg_aggregate_agginitval,
+								  &initValueIsNull);
+	if (initValueIsNull)
+		initValue = (Datum) 0;
+	else
+		initValue = GetAggInitVal(textInitVal, aggtranstype);
+
+	ReleaseSysCache(aggTuple);
+
+	/*
+	 * 1. See if this is identical to another aggregate function call that
+	 * we've seen already.
+	 */
+	aggno = find_compatible_agg(root, aggref, &same_input_transnos);
+	if (aggno != -1)
+	{
+		AggInfo    *agginfo = list_nth(root->agginfos, aggno);
+
+		transno = agginfo->transno;
+	}
+	else
+	{
+		AggInfo    *agginfo = palloc(sizeof(AggInfo));
+
+		agginfo->finalfn_oid = aggfinalfn;
+		agginfo->representative_aggref = aggref;
+		agginfo->shareable = shareable;
+
+		aggno = list_length(root->agginfos);
+		root->agginfos = lappend(root->agginfos, agginfo);
+
+		/*
+		 * Count it, and check for cases requiring ordered input.  Note that
+		 * ordered-set aggs always have nonempty aggorder.  Any ordered-input
+		 * case also defeats partial aggregation.
+		 */
+		if (aggref->aggorder != NIL || aggref->aggdistinct != NIL)
+		{
+			root->numOrderedAggs++;
+			root->hasNonPartialAggs = true;
+		}
+
+		get_typlenbyval(aggtranstype,
+						&transtypeLen,
+						&transtypeByVal);
+
+		/*
+		 * 2. See if this aggregate can share transition state with another
+		 * aggregate that we've initialized already.
+		 */
+		transno = find_compatible_trans(root, aggref, shareable,
+										aggtransfn, aggtranstype,
+										transtypeLen, transtypeByVal,
+										aggcombinefn,
+										aggserialfn, aggdeserialfn,
+										initValue, initValueIsNull,
+										same_input_transnos);
+		if (transno == -1)
+		{
+			AggTransInfo *transinfo = palloc(sizeof(AggTransInfo));
+
+			transinfo->args = aggref->args;
+			transinfo->aggfilter = aggref->aggfilter;
+			transinfo->transfn_oid = aggtransfn;
+			transinfo->combinefn_oid = aggcombinefn;
+			transinfo->serialfn_oid = aggserialfn;
+			transinfo->deserialfn_oid = aggdeserialfn;
+			transinfo->aggtranstype = aggtranstype;
+			transinfo->aggtranstypmod = aggtranstypmod;
+			transinfo->transtypeLen = transtypeLen;
+			transinfo->transtypeByVal = transtypeByVal;
+			transinfo->aggtransspace = aggtransspace;
+			transinfo->initValue = initValue;
+			transinfo->initValueIsNull = initValueIsNull;
+
+			transno = list_length(root->aggtransinfos);
+			root->aggtransinfos = lappend(root->aggtransinfos, transinfo);
+
+			/*
+			 * Check whether partial aggregation is feasible, unless we
+			 * already found out that we can't do it.
+			 */
+			if (!root->hasNonPartialAggs)
+			{
+				/*
+				 * If there is no combine function, then partial aggregation
+				 * is not possible.
+				 */
+				if (!OidIsValid(transinfo->combinefn_oid))
+					root->hasNonPartialAggs = true;
+
+				/*
+				 * If we have any aggs with transtype INTERNAL then we must
+				 * check whether they have serialization/deserialization
+				 * functions; if not, we can't serialize partial-aggregation
+				 * results.
+				 */
+				else if (transinfo->aggtranstype == INTERNALOID &&
+						 (!OidIsValid(transinfo->serialfn_oid) ||
+						  !OidIsValid(transinfo->deserialfn_oid)))
+					root->hasNonSerialAggs = true;
+			}
+		}
+		agginfo->transno = transno;
+	}
+
+	/*
+	 * Fill in the fields in the Aggref (aggtranstype was set above already)
+	 */
+	aggref->aggno = aggno;
+	aggref->aggtransno = transno;
+}
+
+static bool
+preprocess_aggrefs_walker(Node *node, PlannerInfo *root)
+{
+	if (node == NULL)
+		return false;
+	if (IsA(node, Aggref))
+	{
+		Aggref	   *aggref = (Aggref *) node;
+
+		preprocess_aggref(aggref, root);
+
+		/*
+		 * We assume that the parser checked that there are no aggregates (of
+		 * this level anyway) in the aggregated arguments, direct arguments,
+		 * or filter clause.  Hence, we need not recurse into any of them.
+		 */
+		return false;
+	}
+	Assert(!IsA(node, SubLink));
+	return expression_tree_walker(node, preprocess_aggrefs_walker,
+								  (void *) root);
+}
+
+
+/*
+ * find_compatible_agg - search for a previously initialized per-Agg struct
+ *
+ * Searches the previously looked at aggregates to find one which is compatible
+ * with this one, with the same input parameters.  If no compatible aggregate
+ * can be found, returns -1.
+ *
+ * As a side-effect, this also collects a list of existing, shareable per-Trans
+ * structs with matching inputs.  If no identical Aggref is found, the list is
+ * passed later to find_compatible_trans, to see if we can at least reuse
+ * the state value of another aggregate.
+ */
+static int
+find_compatible_agg(PlannerInfo *root, Aggref *newagg,
+					List **same_input_transnos)
+{
+	ListCell   *lc;
+	int			aggno;
+
+	*same_input_transnos = NIL;
+
+	/* we mustn't reuse the aggref if it contains volatile function calls */
+	if (contain_volatile_functions((Node *) newagg))
+		return -1;
+
+	/*
+	 * Search through the list of already seen aggregates.  If we find an
+	 * existing identical aggregate call, then we can re-use that one.  While
+	 * searching, we'll also collect a list of Aggrefs with the same input
+	 * parameters.  If no matching Aggref is found, the caller can potentially
+	 * still re-use the transition state of one of them.  (At this stage we
+	 * just compare the parsetrees; whether different aggregates share the
+	 * same transition function will be checked later.)
+	 */
+	aggno = -1;
+	foreach(lc, root->agginfos)
+	{
+		AggInfo    *agginfo = (AggInfo *) lfirst(lc);
+		Aggref	   *existingRef;
+
+		aggno++;
+
+		existingRef = agginfo->representative_aggref;
+
+		/* all of the following must be the same or it's no match */
+		if (newagg->inputcollid != existingRef->inputcollid ||
+			newagg->aggtranstype != existingRef->aggtranstype ||
+			newagg->aggstar != existingRef->aggstar ||
+			newagg->aggvariadic != existingRef->aggvariadic ||
+			newagg->aggkind != existingRef->aggkind ||
+			!equal(newagg->args, existingRef->args) ||
+			!equal(newagg->aggorder, existingRef->aggorder) ||
+			!equal(newagg->aggdistinct, existingRef->aggdistinct) ||
+			!equal(newagg->aggfilter, existingRef->aggfilter))
+			continue;
+
+		/* if it's the same aggregate function then report exact match */
+		if (newagg->aggfnoid == existingRef->aggfnoid &&
+			newagg->aggtype == existingRef->aggtype &&
+			newagg->aggcollid == existingRef->aggcollid &&
+			equal(newagg->aggdirectargs, existingRef->aggdirectargs))
+		{
+			list_free(*same_input_transnos);
+			*same_input_transnos = NIL;
+			return aggno;
+		}
+
+		/*
+		 * Not identical, but it had the same inputs.  If the final function
+		 * permits sharing, return its transno to the caller, in case we can
+		 * re-use its per-trans state.  (If there's already sharing going on,
+		 * we might report a transno more than once.  find_compatible_trans is
+		 * cheap enough that it's not worth spending cycles to avoid that.)
+		 */
+		if (agginfo->shareable)
+			*same_input_transnos = lappend_int(*same_input_transnos,
+											   agginfo->transno);
+	}
+
+	return -1;
+}
+
+/*
+ * find_compatible_trans - search for a previously initialized per-Trans
+ * struct
+ *
+ * Searches the list of transnos for a per-Trans struct with the same
+ * transition function and initial condition. (The inputs have already been
+ * verified to match.)
+ */
+static int
+find_compatible_trans(PlannerInfo *root, Aggref *newagg, bool shareable,
+					  Oid aggtransfn, Oid aggtranstype,
+					  int transtypeLen, bool transtypeByVal,
+					  Oid aggcombinefn,
+					  Oid aggserialfn, Oid aggdeserialfn,
+					  Datum initValue, bool initValueIsNull,
+					  List *transnos)
+{
+	ListCell   *lc;
+
+	/* If this aggregate can't share transition states, give up */
+	if (!shareable)
+		return -1;
+
+	foreach(lc, transnos)
+	{
+		int			transno = lfirst_int(lc);
+		AggTransInfo *pertrans = (AggTransInfo *) list_nth(root->aggtransinfos, transno);
+
+		/*
+		 * if the transfns or transition state types are not the same then the
+		 * state can't be shared.
+		 */
+		if (aggtransfn != pertrans->transfn_oid ||
+			aggtranstype != pertrans->aggtranstype)
+			continue;
+
+		/*
+		 * The serialization and deserialization functions must match, if
+		 * present, as we're unable to share the trans state for aggregates
+		 * which will serialize or deserialize into different formats.
+		 * Remember that these will be InvalidOid if they're not required for
+		 * this agg node.
+		 */
+		if (aggserialfn != pertrans->serialfn_oid ||
+			aggdeserialfn != pertrans->deserialfn_oid)
+			continue;
+
+		/*
+		 * Combine function must also match.  We only care about the combine
+		 * function with partial aggregates, but it's too early in the
+		 * planning to know if we will do partial aggregation, so be
+		 * conservative.
+		 */
+		if (aggcombinefn != pertrans->combinefn_oid)
+			continue;
+
+		/*
+		 * Check that the initial condition matches, too.
+		 */
+		if (initValueIsNull && pertrans->initValueIsNull)
+			return transno;
+
+		if (!initValueIsNull && !pertrans->initValueIsNull &&
+			datumIsEqual(initValue, pertrans->initValue,
+						 transtypeByVal, transtypeLen))
+			return transno;
+	}
+	return -1;
+}
+
+static Datum
+GetAggInitVal(Datum textInitVal, Oid transtype)
+{
+	Oid			typinput,
+				typioparam;
+	char	   *strInitVal;
+	Datum		initVal;
+
+	getTypeInputInfo(transtype, &typinput, &typioparam);
+	strInitVal = TextDatumGetCString(textInitVal);
+	initVal = OidInputFunctionCall(typinput, strInitVal,
+								   typioparam, -1);
+	pfree(strInitVal);
+	return initVal;
+}
+
+
+/*
+ * get_agg_clause_costs
+ *	  Process the PlannerInfo's 'aggtransinfos' and 'agginfos' lists
+ *	  accumulating the cost information about them.
+ *
+ * 'aggsplit' tells us the expected partial-aggregation mode, which affects
+ * the cost estimates.
+ *
+ * NOTE that the costs are ADDED to those already in *costs ... so the caller
+ * is responsible for zeroing the struct initially.
+ *
+ * For each AggTransInfo, we add the cost of an aggregate transition using
+ * either the transfn or combinefn depending on the 'aggsplit' value.  We also
+ * account for the costs of any aggfilters and any serializations and
+ * deserializations of the transition state and also estimate the total space
+ * needed for the transition states as if each aggregate's state was stored in
+ * memory concurrently (as would be done in a HashAgg plan).
+ *
+ * For each AggInfo in the 'agginfos' list we add the cost of running the
+ * final function and the direct args, if any.
+ */
+void
+get_agg_clause_costs(PlannerInfo *root, AggSplit aggsplit, AggClauseCosts *costs)
+{
+	ListCell   *lc;
+
+	foreach(lc, root->aggtransinfos)
+	{
+		AggTransInfo *transinfo = (AggTransInfo *) lfirst(lc);
+
+		/*
+		 * Add the appropriate component function execution costs to
+		 * appropriate totals.
+		 */
+		if (DO_AGGSPLIT_COMBINE(aggsplit))
+		{
+			/* charge for combining previously aggregated states */
+			add_function_cost(root, transinfo->combinefn_oid, NULL,
+							  &costs->transCost);
+		}
+		else
+			add_function_cost(root, transinfo->transfn_oid, NULL,
+							  &costs->transCost);
+		if (DO_AGGSPLIT_DESERIALIZE(aggsplit) &&
+			OidIsValid(transinfo->deserialfn_oid))
+			add_function_cost(root, transinfo->deserialfn_oid, NULL,
+							  &costs->transCost);
+		if (DO_AGGSPLIT_SERIALIZE(aggsplit) &&
+			OidIsValid(transinfo->serialfn_oid))
+			add_function_cost(root, transinfo->serialfn_oid, NULL,
+							  &costs->finalCost);
+
+		/*
+		 * These costs are incurred only by the initial aggregate node, so we
+		 * mustn't include them again at upper levels.
+		 */
+		if (!DO_AGGSPLIT_COMBINE(aggsplit))
+		{
+			/* add the input expressions' cost to per-input-row costs */
+			QualCost	argcosts;
+
+			cost_qual_eval_node(&argcosts, (Node *) transinfo->args, root);
+			costs->transCost.startup += argcosts.startup;
+			costs->transCost.per_tuple += argcosts.per_tuple;
+
+			/*
+			 * Add any filter's cost to per-input-row costs.
+			 *
+			 * XXX Ideally we should reduce input expression costs according
+			 * to filter selectivity, but it's not clear it's worth the
+			 * trouble.
+			 */
+			if (transinfo->aggfilter)
+			{
+				cost_qual_eval_node(&argcosts, (Node *) transinfo->aggfilter,
+									root);
+				costs->transCost.startup += argcosts.startup;
+				costs->transCost.per_tuple += argcosts.per_tuple;
+			}
+		}
+
+		/*
+		 * If the transition type is pass-by-value then it doesn't add
+		 * anything to the required size of the hashtable.  If it is
+		 * pass-by-reference then we have to add the estimated size of the
+		 * value itself, plus palloc overhead.
+		 */
+		if (!transinfo->transtypeByVal)
+		{
+			int32		avgwidth;
+
+			/* Use average width if aggregate definition gave one */
+			if (transinfo->aggtransspace > 0)
+				avgwidth = transinfo->aggtransspace;
+			else if (transinfo->transfn_oid == F_ARRAY_APPEND)
+			{
+				/*
+				 * If the transition function is array_append(), it'll use an
+				 * expanded array as transvalue, which will occupy at least
+				 * ALLOCSET_SMALL_INITSIZE and possibly more.  Use that as the
+				 * estimate for lack of a better idea.
+				 */
+				avgwidth = ALLOCSET_SMALL_INITSIZE;
+			}
+			else
+			{
+				avgwidth = get_typavgwidth(transinfo->aggtranstype, transinfo->aggtranstypmod);
+			}
+
+			avgwidth = MAXALIGN(avgwidth);
+			costs->transitionSpace += avgwidth + 2 * sizeof(void *);
+		}
+		else if (transinfo->aggtranstype == INTERNALOID)
+		{
+			/*
+			 * INTERNAL transition type is a special case: although INTERNAL
+			 * is pass-by-value, it's almost certainly being used as a pointer
+			 * to some large data structure.  The aggregate definition can
+			 * provide an estimate of the size.  If it doesn't, then we assume
+			 * ALLOCSET_DEFAULT_INITSIZE, which is a good guess if the data is
+			 * being kept in a private memory context, as is done by
+			 * array_agg() for instance.
+			 */
+			if (transinfo->aggtransspace > 0)
+				costs->transitionSpace += transinfo->aggtransspace;
+			else
+				costs->transitionSpace += ALLOCSET_DEFAULT_INITSIZE;
+		}
+	}
+
+	foreach(lc, root->agginfos)
+	{
+		AggInfo    *agginfo = (AggInfo *) lfirst(lc);
+		Aggref	   *aggref = agginfo->representative_aggref;
+
+		/*
+		 * Add the appropriate component function execution costs to
+		 * appropriate totals.
+		 */
+		if (!DO_AGGSPLIT_SKIPFINAL(aggsplit) &&
+			OidIsValid(agginfo->finalfn_oid))
+			add_function_cost(root, agginfo->finalfn_oid, NULL,
+							  &costs->finalCost);
+
+		/*
+		 * If there are direct arguments, treat their evaluation cost like the
+		 * cost of the finalfn.
+		 */
+		if (aggref->aggdirectargs)
+		{
+			QualCost	argcosts;
+
+			cost_qual_eval_node(&argcosts, (Node *) aggref->aggdirectargs,
+								root);
+			costs->finalCost.startup += argcosts.startup;
+			costs->finalCost.per_tuple += argcosts.per_tuple;
+		}
+	}
+}
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
new file mode 100644
index 0000000..b164866
--- /dev/null
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -0,0 +1,3633 @@
+/*-------------------------------------------------------------------------
+ *
+ * prepjointree.c
+ *	  Planner preprocessing for subqueries and join tree manipulation.
+ *
+ * NOTE: the intended sequence for invoking these operations is
+ *		replace_empty_jointree
+ *		pull_up_sublinks
+ *		preprocess_function_rtes
+ *		pull_up_subqueries
+ *		flatten_simple_union_all
+ *		do expression preprocessing (including flattening JOIN alias vars)
+ *		reduce_outer_joins
+ *		remove_useless_result_rtes
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/prep/prepjointree.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "catalog/pg_type.h"
+#include "funcapi.h"
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/clauses.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/placeholder.h"
+#include "optimizer/prep.h"
+#include "optimizer/subselect.h"
+#include "optimizer/tlist.h"
+#include "parser/parse_relation.h"
+#include "parser/parsetree.h"
+#include "rewrite/rewriteManip.h"
+
+
+typedef struct pullup_replace_vars_context
+{
+	PlannerInfo *root;
+	List	   *targetlist;		/* tlist of subquery being pulled up */
+	RangeTblEntry *target_rte;	/* RTE of subquery */
+	Relids		relids;			/* relids within subquery, as numbered after
+								 * pullup (set only if target_rte->lateral) */
+	bool	   *outer_hasSubLinks;	/* -> outer query's hasSubLinks */
+	int			varno;			/* varno of subquery */
+	bool		need_phvs;		/* do we need PlaceHolderVars? */
+	bool		wrap_non_vars;	/* do we need 'em on *all* non-Vars? */
+	Node	  **rv_cache;		/* cache for results with PHVs */
+} pullup_replace_vars_context;
+
+typedef struct reduce_outer_joins_state
+{
+	Relids		relids;			/* base relids within this subtree */
+	bool		contains_outer; /* does subtree contain outer join(s)? */
+	List	   *sub_states;		/* List of states for subtree components */
+} reduce_outer_joins_state;
+
+static Node *pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
+											   Relids *relids);
+static Node *pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
+										   Node **jtlink1, Relids available_rels1,
+										   Node **jtlink2, Relids available_rels2);
+static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
+										JoinExpr *lowest_outer_join,
+										JoinExpr *lowest_nulling_outer_join,
+										AppendRelInfo *containing_appendrel);
+static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
+									 RangeTblEntry *rte,
+									 JoinExpr *lowest_outer_join,
+									 JoinExpr *lowest_nulling_outer_join,
+									 AppendRelInfo *containing_appendrel);
+static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
+									  RangeTblEntry *rte);
+static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
+									   int parentRTindex, Query *setOpQuery,
+									   int childRToffset);
+static void make_setop_translation_list(Query *query, Index newvarno,
+										AppendRelInfo *appinfo);
+static bool is_simple_subquery(PlannerInfo *root, Query *subquery,
+							   RangeTblEntry *rte,
+							   JoinExpr *lowest_outer_join);
+static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
+								   RangeTblEntry *rte);
+static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte);
+static Node *pull_up_constant_function(PlannerInfo *root, Node *jtnode,
+									   RangeTblEntry *rte,
+									   JoinExpr *lowest_nulling_outer_join,
+									   AppendRelInfo *containing_appendrel);
+static bool is_simple_union_all(Query *subquery);
+static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
+										List *colTypes);
+static bool is_safe_append_member(Query *subquery);
+static bool jointree_contains_lateral_outer_refs(PlannerInfo *root,
+												 Node *jtnode, bool restricted,
+												 Relids safe_upper_varnos);
+static void perform_pullup_replace_vars(PlannerInfo *root,
+										pullup_replace_vars_context *rvcontext,
+										JoinExpr *lowest_nulling_outer_join,
+										AppendRelInfo *containing_appendrel);
+static void replace_vars_in_jointree(Node *jtnode,
+									 pullup_replace_vars_context *context,
+									 JoinExpr *lowest_nulling_outer_join);
+static Node *pullup_replace_vars(Node *expr,
+								 pullup_replace_vars_context *context);
+static Node *pullup_replace_vars_callback(Var *var,
+										  replace_rte_variables_context *context);
+static Query *pullup_replace_vars_subquery(Query *query,
+										   pullup_replace_vars_context *context);
+static reduce_outer_joins_state *reduce_outer_joins_pass1(Node *jtnode);
+static void reduce_outer_joins_pass2(Node *jtnode,
+									 reduce_outer_joins_state *state,
+									 PlannerInfo *root,
+									 Relids nonnullable_rels,
+									 List *nonnullable_vars,
+									 List *forced_null_vars);
+static Node *remove_useless_results_recurse(PlannerInfo *root, Node *jtnode);
+static int	get_result_relid(PlannerInfo *root, Node *jtnode);
+static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc);
+static bool find_dependent_phvs(PlannerInfo *root, int varno);
+static bool find_dependent_phvs_in_jointree(PlannerInfo *root,
+											Node *node, int varno);
+static void substitute_phv_relids(Node *node,
+								  int varno, Relids subrelids);
+static void fix_append_rel_relids(List *append_rel_list, int varno,
+								  Relids subrelids);
+static Node *find_jointree_node_for_rel(Node *jtnode, int relid);
+
+
+/*
+ * replace_empty_jointree
+ *		If the Query's jointree is empty, replace it with a dummy RTE_RESULT
+ *		relation.
+ *
+ * By doing this, we can avoid a bunch of corner cases that formerly existed
+ * for SELECTs with omitted FROM clauses.  An example is that a subquery
+ * with empty jointree previously could not be pulled up, because that would
+ * have resulted in an empty relid set, making the subquery not uniquely
+ * identifiable for join or PlaceHolderVar processing.
+ *
+ * Unlike most other functions in this file, this function doesn't recurse;
+ * we rely on other processing to invoke it on sub-queries at suitable times.
+ */
+void
+replace_empty_jointree(Query *parse)
+{
+	RangeTblEntry *rte;
+	Index		rti;
+	RangeTblRef *rtr;
+
+	/* Nothing to do if jointree is already nonempty */
+	if (parse->jointree->fromlist != NIL)
+		return;
+
+	/* We mustn't change it in the top level of a setop tree, either */
+	if (parse->setOperations)
+		return;
+
+	/* Create suitable RTE */
+	rte = makeNode(RangeTblEntry);
+	rte->rtekind = RTE_RESULT;
+	rte->eref = makeAlias("*RESULT*", NIL);
+
+	/* Add it to rangetable */
+	parse->rtable = lappend(parse->rtable, rte);
+	rti = list_length(parse->rtable);
+
+	/* And jam a reference into the jointree */
+	rtr = makeNode(RangeTblRef);
+	rtr->rtindex = rti;
+	parse->jointree->fromlist = list_make1(rtr);
+}
+
+/*
+ * pull_up_sublinks
+ *		Attempt to pull up ANY and EXISTS SubLinks to be treated as
+ *		semijoins or anti-semijoins.
+ *
+ * A clause "foo op ANY (sub-SELECT)" can be processed by pulling the
+ * sub-SELECT up to become a rangetable entry and treating the implied
+ * comparisons as quals of a semijoin.  However, this optimization *only*
+ * works at the top level of WHERE or a JOIN/ON clause, because we cannot
+ * distinguish whether the ANY ought to return FALSE or NULL in cases
+ * involving NULL inputs.  Also, in an outer join's ON clause we can only
+ * do this if the sublink is degenerate (ie, references only the nullable
+ * side of the join).  In that case it is legal to push the semijoin
+ * down into the nullable side of the join.  If the sublink references any
+ * nonnullable-side variables then it would have to be evaluated as part
+ * of the outer join, which makes things way too complicated.
+ *
+ * Under similar conditions, EXISTS and NOT EXISTS clauses can be handled
+ * by pulling up the sub-SELECT and creating a semijoin or anti-semijoin.
+ *
+ * This routine searches for such clauses and does the necessary parsetree
+ * transformations if any are found.
+ *
+ * This routine has to run before preprocess_expression(), so the quals
+ * clauses are not yet reduced to implicit-AND format, and are not guaranteed
+ * to be AND/OR-flat either.  That means we need to recursively search through
+ * explicit AND clauses.  We stop as soon as we hit a non-AND item.
+ */
+void
+pull_up_sublinks(PlannerInfo *root)
+{
+	Node	   *jtnode;
+	Relids		relids;
+
+	/* Begin recursion through the jointree */
+	jtnode = pull_up_sublinks_jointree_recurse(root,
+											   (Node *) root->parse->jointree,
+											   &relids);
+
+	/*
+	 * root->parse->jointree must always be a FromExpr, so insert a dummy one
+	 * if we got a bare RangeTblRef or JoinExpr out of the recursion.
+	 */
+	if (IsA(jtnode, FromExpr))
+		root->parse->jointree = (FromExpr *) jtnode;
+	else
+		root->parse->jointree = makeFromExpr(list_make1(jtnode), NULL);
+}
+
+/*
+ * Recurse through jointree nodes for pull_up_sublinks()
+ *
+ * In addition to returning the possibly-modified jointree node, we return
+ * a relids set of the contained rels into *relids.
+ */
+static Node *
+pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
+								  Relids *relids)
+{
+	if (jtnode == NULL)
+	{
+		*relids = NULL;
+	}
+	else if (IsA(jtnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+
+		*relids = bms_make_singleton(varno);
+		/* jtnode is returned unmodified */
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		List	   *newfromlist = NIL;
+		Relids		frelids = NULL;
+		FromExpr   *newf;
+		Node	   *jtlink;
+		ListCell   *l;
+
+		/* First, recurse to process children and collect their relids */
+		foreach(l, f->fromlist)
+		{
+			Node	   *newchild;
+			Relids		childrelids;
+
+			newchild = pull_up_sublinks_jointree_recurse(root,
+														 lfirst(l),
+														 &childrelids);
+			newfromlist = lappend(newfromlist, newchild);
+			frelids = bms_join(frelids, childrelids);
+		}
+		/* Build the replacement FromExpr; no quals yet */
+		newf = makeFromExpr(newfromlist, NULL);
+		/* Set up a link representing the rebuilt jointree */
+		jtlink = (Node *) newf;
+		/* Now process qual --- all children are available for use */
+		newf->quals = pull_up_sublinks_qual_recurse(root, f->quals,
+													&jtlink, frelids,
+													NULL, NULL);
+
+		/*
+		 * Note that the result will be either newf, or a stack of JoinExprs
+		 * with newf at the base.  We rely on subsequent optimization steps to
+		 * flatten this and rearrange the joins as needed.
+		 *
+		 * Although we could include the pulled-up subqueries in the returned
+		 * relids, there's no need since upper quals couldn't refer to their
+		 * outputs anyway.
+		 */
+		*relids = frelids;
+		jtnode = jtlink;
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j;
+		Relids		leftrelids;
+		Relids		rightrelids;
+		Node	   *jtlink;
+
+		/*
+		 * Make a modifiable copy of join node, but don't bother copying its
+		 * subnodes (yet).
+		 */
+		j = (JoinExpr *) palloc(sizeof(JoinExpr));
+		memcpy(j, jtnode, sizeof(JoinExpr));
+		jtlink = (Node *) j;
+
+		/* Recurse to process children and collect their relids */
+		j->larg = pull_up_sublinks_jointree_recurse(root, j->larg,
+													&leftrelids);
+		j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg,
+													&rightrelids);
+
+		/*
+		 * Now process qual, showing appropriate child relids as available,
+		 * and attach any pulled-up jointree items at the right place. In the
+		 * inner-join case we put new JoinExprs above the existing one (much
+		 * as for a FromExpr-style join).  In outer-join cases the new
+		 * JoinExprs must go into the nullable side of the outer join. The
+		 * point of the available_rels machinations is to ensure that we only
+		 * pull up quals for which that's okay.
+		 *
+		 * We don't expect to see any pre-existing JOIN_SEMI or JOIN_ANTI
+		 * nodes here.
+		 */
+		switch (j->jointype)
+		{
+			case JOIN_INNER:
+				j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
+														 &jtlink,
+														 bms_union(leftrelids,
+																   rightrelids),
+														 NULL, NULL);
+				break;
+			case JOIN_LEFT:
+				j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
+														 &j->rarg,
+														 rightrelids,
+														 NULL, NULL);
+				break;
+			case JOIN_FULL:
+				/* can't do anything with full-join quals */
+				break;
+			case JOIN_RIGHT:
+				j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
+														 &j->larg,
+														 leftrelids,
+														 NULL, NULL);
+				break;
+			default:
+				elog(ERROR, "unrecognized join type: %d",
+					 (int) j->jointype);
+				break;
+		}
+
+		/*
+		 * Although we could include the pulled-up subqueries in the returned
+		 * relids, there's no need since upper quals couldn't refer to their
+		 * outputs anyway.  But we *do* need to include the join's own rtindex
+		 * because we haven't yet collapsed join alias variables, so upper
+		 * levels would mistakenly think they couldn't use references to this
+		 * join.
+		 */
+		*relids = bms_join(leftrelids, rightrelids);
+		if (j->rtindex)
+			*relids = bms_add_member(*relids, j->rtindex);
+		jtnode = jtlink;
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return jtnode;
+}
+
+/*
+ * Recurse through top-level qual nodes for pull_up_sublinks()
+ *
+ * jtlink1 points to the link in the jointree where any new JoinExprs should
+ * be inserted if they reference available_rels1 (i.e., available_rels1
+ * denotes the relations present underneath jtlink1).  Optionally, jtlink2 can
+ * point to a second link where new JoinExprs should be inserted if they
+ * reference available_rels2 (pass NULL for both those arguments if not used).
+ * Note that SubLinks referencing both sets of variables cannot be optimized.
+ * If we find multiple pull-up-able SubLinks, they'll get stacked onto jtlink1
+ * and/or jtlink2 in the order we encounter them.  We rely on subsequent
+ * optimization to rearrange the stack if appropriate.
+ *
+ * Returns the replacement qual node, or NULL if the qual should be removed.
+ */
+static Node *
+pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
+							  Node **jtlink1, Relids available_rels1,
+							  Node **jtlink2, Relids available_rels2)
+{
+	if (node == NULL)
+		return NULL;
+	if (IsA(node, SubLink))
+	{
+		SubLink    *sublink = (SubLink *) node;
+		JoinExpr   *j;
+		Relids		child_rels;
+
+		/* Is it a convertible ANY or EXISTS clause? */
+		if (sublink->subLinkType == ANY_SUBLINK)
+		{
+			if ((j = convert_ANY_sublink_to_join(root, sublink,
+												 available_rels1)) != NULL)
+			{
+				/* Yes; insert the new join node into the join tree */
+				j->larg = *jtlink1;
+				*jtlink1 = (Node *) j;
+				/* Recursively process pulled-up jointree nodes */
+				j->rarg = pull_up_sublinks_jointree_recurse(root,
+															j->rarg,
+															&child_rels);
+
+				/*
+				 * Now recursively process the pulled-up quals.  Any inserted
+				 * joins can get stacked onto either j->larg or j->rarg,
+				 * depending on which rels they reference.
+				 */
+				j->quals = pull_up_sublinks_qual_recurse(root,
+														 j->quals,
+														 &j->larg,
+														 available_rels1,
+														 &j->rarg,
+														 child_rels);
+				/* Return NULL representing constant TRUE */
+				return NULL;
+			}
+			if (available_rels2 != NULL &&
+				(j = convert_ANY_sublink_to_join(root, sublink,
+												 available_rels2)) != NULL)
+			{
+				/* Yes; insert the new join node into the join tree */
+				j->larg = *jtlink2;
+				*jtlink2 = (Node *) j;
+				/* Recursively process pulled-up jointree nodes */
+				j->rarg = pull_up_sublinks_jointree_recurse(root,
+															j->rarg,
+															&child_rels);
+
+				/*
+				 * Now recursively process the pulled-up quals.  Any inserted
+				 * joins can get stacked onto either j->larg or j->rarg,
+				 * depending on which rels they reference.
+				 */
+				j->quals = pull_up_sublinks_qual_recurse(root,
+														 j->quals,
+														 &j->larg,
+														 available_rels2,
+														 &j->rarg,
+														 child_rels);
+				/* Return NULL representing constant TRUE */
+				return NULL;
+			}
+		}
+		else if (sublink->subLinkType == EXISTS_SUBLINK)
+		{
+			if ((j = convert_EXISTS_sublink_to_join(root, sublink, false,
+													available_rels1)) != NULL)
+			{
+				/* Yes; insert the new join node into the join tree */
+				j->larg = *jtlink1;
+				*jtlink1 = (Node *) j;
+				/* Recursively process pulled-up jointree nodes */
+				j->rarg = pull_up_sublinks_jointree_recurse(root,
+															j->rarg,
+															&child_rels);
+
+				/*
+				 * Now recursively process the pulled-up quals.  Any inserted
+				 * joins can get stacked onto either j->larg or j->rarg,
+				 * depending on which rels they reference.
+				 */
+				j->quals = pull_up_sublinks_qual_recurse(root,
+														 j->quals,
+														 &j->larg,
+														 available_rels1,
+														 &j->rarg,
+														 child_rels);
+				/* Return NULL representing constant TRUE */
+				return NULL;
+			}
+			if (available_rels2 != NULL &&
+				(j = convert_EXISTS_sublink_to_join(root, sublink, false,
+													available_rels2)) != NULL)
+			{
+				/* Yes; insert the new join node into the join tree */
+				j->larg = *jtlink2;
+				*jtlink2 = (Node *) j;
+				/* Recursively process pulled-up jointree nodes */
+				j->rarg = pull_up_sublinks_jointree_recurse(root,
+															j->rarg,
+															&child_rels);
+
+				/*
+				 * Now recursively process the pulled-up quals.  Any inserted
+				 * joins can get stacked onto either j->larg or j->rarg,
+				 * depending on which rels they reference.
+				 */
+				j->quals = pull_up_sublinks_qual_recurse(root,
+														 j->quals,
+														 &j->larg,
+														 available_rels2,
+														 &j->rarg,
+														 child_rels);
+				/* Return NULL representing constant TRUE */
+				return NULL;
+			}
+		}
+		/* Else return it unmodified */
+		return node;
+	}
+	if (is_notclause(node))
+	{
+		/* If the immediate argument of NOT is EXISTS, try to convert */
+		SubLink    *sublink = (SubLink *) get_notclausearg((Expr *) node);
+		JoinExpr   *j;
+		Relids		child_rels;
+
+		if (sublink && IsA(sublink, SubLink))
+		{
+			if (sublink->subLinkType == EXISTS_SUBLINK)
+			{
+				if ((j = convert_EXISTS_sublink_to_join(root, sublink, true,
+														available_rels1)) != NULL)
+				{
+					/* Yes; insert the new join node into the join tree */
+					j->larg = *jtlink1;
+					*jtlink1 = (Node *) j;
+					/* Recursively process pulled-up jointree nodes */
+					j->rarg = pull_up_sublinks_jointree_recurse(root,
+																j->rarg,
+																&child_rels);
+
+					/*
+					 * Now recursively process the pulled-up quals.  Because
+					 * we are underneath a NOT, we can't pull up sublinks that
+					 * reference the left-hand stuff, but it's still okay to
+					 * pull up sublinks referencing j->rarg.
+					 */
+					j->quals = pull_up_sublinks_qual_recurse(root,
+															 j->quals,
+															 &j->rarg,
+															 child_rels,
+															 NULL, NULL);
+					/* Return NULL representing constant TRUE */
+					return NULL;
+				}
+				if (available_rels2 != NULL &&
+					(j = convert_EXISTS_sublink_to_join(root, sublink, true,
+														available_rels2)) != NULL)
+				{
+					/* Yes; insert the new join node into the join tree */
+					j->larg = *jtlink2;
+					*jtlink2 = (Node *) j;
+					/* Recursively process pulled-up jointree nodes */
+					j->rarg = pull_up_sublinks_jointree_recurse(root,
+																j->rarg,
+																&child_rels);
+
+					/*
+					 * Now recursively process the pulled-up quals.  Because
+					 * we are underneath a NOT, we can't pull up sublinks that
+					 * reference the left-hand stuff, but it's still okay to
+					 * pull up sublinks referencing j->rarg.
+					 */
+					j->quals = pull_up_sublinks_qual_recurse(root,
+															 j->quals,
+															 &j->rarg,
+															 child_rels,
+															 NULL, NULL);
+					/* Return NULL representing constant TRUE */
+					return NULL;
+				}
+			}
+		}
+		/* Else return it unmodified */
+		return node;
+	}
+	if (is_andclause(node))
+	{
+		/* Recurse into AND clause */
+		List	   *newclauses = NIL;
+		ListCell   *l;
+
+		foreach(l, ((BoolExpr *) node)->args)
+		{
+			Node	   *oldclause = (Node *) lfirst(l);
+			Node	   *newclause;
+
+			newclause = pull_up_sublinks_qual_recurse(root,
+													  oldclause,
+													  jtlink1,
+													  available_rels1,
+													  jtlink2,
+													  available_rels2);
+			if (newclause)
+				newclauses = lappend(newclauses, newclause);
+		}
+		/* We might have got back fewer clauses than we started with */
+		if (newclauses == NIL)
+			return NULL;
+		else if (list_length(newclauses) == 1)
+			return (Node *) linitial(newclauses);
+		else
+			return (Node *) make_andclause(newclauses);
+	}
+	/* Stop if not an AND */
+	return node;
+}
+
+/*
+ * preprocess_function_rtes
+ *		Constant-simplify any FUNCTION RTEs in the FROM clause, and then
+ *		attempt to "inline" any that are set-returning functions.
+ *
+ * If an RTE_FUNCTION rtable entry invokes a set-returning function that
+ * contains just a simple SELECT, we can convert the rtable entry to an
+ * RTE_SUBQUERY entry exposing the SELECT directly.  This is especially
+ * useful if the subquery can then be "pulled up" for further optimization,
+ * but we do it even if not, to reduce executor overhead.
+ *
+ * This has to be done before we have started to do any optimization of
+ * subqueries, else any such steps wouldn't get applied to subqueries
+ * obtained via inlining.  However, we do it after pull_up_sublinks
+ * so that we can inline any functions used in SubLink subselects.
+ *
+ * The reason for applying const-simplification at this stage is that
+ * (a) we'd need to do it anyway to inline a SRF, and (b) by doing it now,
+ * we can be sure that pull_up_constant_function() will see constants
+ * if there are constants to be seen.  This approach also guarantees
+ * that every FUNCTION RTE has been const-simplified, allowing planner.c's
+ * preprocess_expression() to skip doing it again.
+ *
+ * Like most of the planner, this feels free to scribble on its input data
+ * structure.
+ */
+void
+preprocess_function_rtes(PlannerInfo *root)
+{
+	ListCell   *rt;
+
+	foreach(rt, root->parse->rtable)
+	{
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
+
+		if (rte->rtekind == RTE_FUNCTION)
+		{
+			Query	   *funcquery;
+
+			/* Apply const-simplification */
+			rte->functions = (List *)
+				eval_const_expressions(root, (Node *) rte->functions);
+
+			/* Check safety of expansion, and expand if possible */
+			funcquery = inline_set_returning_function(root, rte);
+			if (funcquery)
+			{
+				/* Successful expansion, convert the RTE to a subquery */
+				rte->rtekind = RTE_SUBQUERY;
+				rte->subquery = funcquery;
+				rte->security_barrier = false;
+				/* Clear fields that should not be set in a subquery RTE */
+				rte->functions = NIL;
+				rte->funcordinality = false;
+			}
+		}
+	}
+}
+
+/*
+ * pull_up_subqueries
+ *		Look for subqueries in the rangetable that can be pulled up into
+ *		the parent query.  If the subquery has no special features like
+ *		grouping/aggregation then we can merge it into the parent's jointree.
+ *		Also, subqueries that are simple UNION ALL structures can be
+ *		converted into "append relations".
+ */
+void
+pull_up_subqueries(PlannerInfo *root)
+{
+	/* Top level of jointree must always be a FromExpr */
+	Assert(IsA(root->parse->jointree, FromExpr));
+	/* Recursion starts with no containing join nor appendrel */
+	root->parse->jointree = (FromExpr *)
+		pull_up_subqueries_recurse(root, (Node *) root->parse->jointree,
+								   NULL, NULL, NULL);
+	/* We should still have a FromExpr */
+	Assert(IsA(root->parse->jointree, FromExpr));
+}
+
+/*
+ * pull_up_subqueries_recurse
+ *		Recursive guts of pull_up_subqueries.
+ *
+ * This recursively processes the jointree and returns a modified jointree.
+ *
+ * If this jointree node is within either side of an outer join, then
+ * lowest_outer_join references the lowest such JoinExpr node; otherwise
+ * it is NULL.  We use this to constrain the effects of LATERAL subqueries.
+ *
+ * If this jointree node is within the nullable side of an outer join, then
+ * lowest_nulling_outer_join references the lowest such JoinExpr node;
+ * otherwise it is NULL.  This forces use of the PlaceHolderVar mechanism for
+ * references to non-nullable targetlist items, but only for references above
+ * that join.
+ *
+ * If we are looking at a member subquery of an append relation,
+ * containing_appendrel describes that relation; else it is NULL.
+ * This forces use of the PlaceHolderVar mechanism for all non-Var targetlist
+ * items, and puts some additional restrictions on what can be pulled up.
+ *
+ * A tricky aspect of this code is that if we pull up a subquery we have
+ * to replace Vars that reference the subquery's outputs throughout the
+ * parent query, including quals attached to jointree nodes above the one
+ * we are currently processing!  We handle this by being careful to maintain
+ * validity of the jointree structure while recursing, in the following sense:
+ * whenever we recurse, all qual expressions in the tree must be reachable
+ * from the top level, in case the recursive call needs to modify them.
+ *
+ * Notice also that we can't turn pullup_replace_vars loose on the whole
+ * jointree, because it'd return a mutated copy of the tree; we have to
+ * invoke it just on the quals, instead.  This behavior is what makes it
+ * reasonable to pass lowest_outer_join and lowest_nulling_outer_join as
+ * pointers rather than some more-indirect way of identifying the lowest
+ * OJs.  Likewise, we don't replace append_rel_list members but only their
+ * substructure, so the containing_appendrel reference is safe to use.
+ */
+static Node *
+pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
+						   JoinExpr *lowest_outer_join,
+						   JoinExpr *lowest_nulling_outer_join,
+						   AppendRelInfo *containing_appendrel)
+{
+	Assert(jtnode != NULL);
+	if (IsA(jtnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+		RangeTblEntry *rte = rt_fetch(varno, root->parse->rtable);
+
+		/*
+		 * Is this a subquery RTE, and if so, is the subquery simple enough to
+		 * pull up?
+		 *
+		 * If we are looking at an append-relation member, we can't pull it up
+		 * unless is_safe_append_member says so.
+		 */
+		if (rte->rtekind == RTE_SUBQUERY &&
+			is_simple_subquery(root, rte->subquery, rte, lowest_outer_join) &&
+			(containing_appendrel == NULL ||
+			 is_safe_append_member(rte->subquery)))
+			return pull_up_simple_subquery(root, jtnode, rte,
+										   lowest_outer_join,
+										   lowest_nulling_outer_join,
+										   containing_appendrel);
+
+		/*
+		 * Alternatively, is it a simple UNION ALL subquery?  If so, flatten
+		 * into an "append relation".
+		 *
+		 * It's safe to do this regardless of whether this query is itself an
+		 * appendrel member.  (If you're thinking we should try to flatten the
+		 * two levels of appendrel together, you're right; but we handle that
+		 * in set_append_rel_pathlist, not here.)
+		 */
+		if (rte->rtekind == RTE_SUBQUERY &&
+			is_simple_union_all(rte->subquery))
+			return pull_up_simple_union_all(root, jtnode, rte);
+
+		/*
+		 * Or perhaps it's a simple VALUES RTE?
+		 *
+		 * We don't allow VALUES pullup below an outer join nor into an
+		 * appendrel (such cases are impossible anyway at the moment).
+		 */
+		if (rte->rtekind == RTE_VALUES &&
+			lowest_outer_join == NULL &&
+			containing_appendrel == NULL &&
+			is_simple_values(root, rte))
+			return pull_up_simple_values(root, jtnode, rte);
+
+		/*
+		 * Or perhaps it's a FUNCTION RTE that we could inline?
+		 */
+		if (rte->rtekind == RTE_FUNCTION)
+			return pull_up_constant_function(root, jtnode, rte,
+											 lowest_nulling_outer_join,
+											 containing_appendrel);
+
+		/* Otherwise, do nothing at this node. */
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		Assert(containing_appendrel == NULL);
+		/* Recursively transform all the child nodes */
+		foreach(l, f->fromlist)
+		{
+			lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
+												   lowest_outer_join,
+												   lowest_nulling_outer_join,
+												   NULL);
+		}
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+
+		Assert(containing_appendrel == NULL);
+		/* Recurse, being careful to tell myself when inside outer join */
+		switch (j->jointype)
+		{
+			case JOIN_INNER:
+				j->larg = pull_up_subqueries_recurse(root, j->larg,
+													 lowest_outer_join,
+													 lowest_nulling_outer_join,
+													 NULL);
+				j->rarg = pull_up_subqueries_recurse(root, j->rarg,
+													 lowest_outer_join,
+													 lowest_nulling_outer_join,
+													 NULL);
+				break;
+			case JOIN_LEFT:
+			case JOIN_SEMI:
+			case JOIN_ANTI:
+				j->larg = pull_up_subqueries_recurse(root, j->larg,
+													 j,
+													 lowest_nulling_outer_join,
+													 NULL);
+				j->rarg = pull_up_subqueries_recurse(root, j->rarg,
+													 j,
+													 j,
+													 NULL);
+				break;
+			case JOIN_FULL:
+				j->larg = pull_up_subqueries_recurse(root, j->larg,
+													 j,
+													 j,
+													 NULL);
+				j->rarg = pull_up_subqueries_recurse(root, j->rarg,
+													 j,
+													 j,
+													 NULL);
+				break;
+			case JOIN_RIGHT:
+				j->larg = pull_up_subqueries_recurse(root, j->larg,
+													 j,
+													 j,
+													 NULL);
+				j->rarg = pull_up_subqueries_recurse(root, j->rarg,
+													 j,
+													 lowest_nulling_outer_join,
+													 NULL);
+				break;
+			default:
+				elog(ERROR, "unrecognized join type: %d",
+					 (int) j->jointype);
+				break;
+		}
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return jtnode;
+}
+
+/*
+ * pull_up_simple_subquery
+ *		Attempt to pull up a single simple subquery.
+ *
+ * jtnode is a RangeTblRef that has been tentatively identified as a simple
+ * subquery by pull_up_subqueries.  We return the replacement jointree node,
+ * or jtnode itself if we determine that the subquery can't be pulled up
+ * after all.
+ *
+ * rte is the RangeTblEntry referenced by jtnode.  Remaining parameters are
+ * as for pull_up_subqueries_recurse.
+ */
+static Node *
+pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
+						JoinExpr *lowest_outer_join,
+						JoinExpr *lowest_nulling_outer_join,
+						AppendRelInfo *containing_appendrel)
+{
+	Query	   *parse = root->parse;
+	int			varno = ((RangeTblRef *) jtnode)->rtindex;
+	Query	   *subquery;
+	PlannerInfo *subroot;
+	int			rtoffset;
+	pullup_replace_vars_context rvcontext;
+	ListCell   *lc;
+
+	/*
+	 * Need a modifiable copy of the subquery to hack on.  Even if we didn't
+	 * sometimes choose not to pull up below, we must do this to avoid
+	 * problems if the same subquery is referenced from multiple jointree
+	 * items (which can't happen normally, but might after rule rewriting).
+	 */
+	subquery = copyObject(rte->subquery);
+
+	/*
+	 * Create a PlannerInfo data structure for this subquery.
+	 *
+	 * NOTE: the next few steps should match the first processing in
+	 * subquery_planner().  Can we refactor to avoid code duplication, or
+	 * would that just make things uglier?
+	 */
+	subroot = makeNode(PlannerInfo);
+	subroot->parse = subquery;
+	subroot->glob = root->glob;
+	subroot->query_level = root->query_level;
+	subroot->parent_root = root->parent_root;
+	subroot->plan_params = NIL;
+	subroot->outer_params = NULL;
+	subroot->planner_cxt = CurrentMemoryContext;
+	subroot->init_plans = NIL;
+	subroot->cte_plan_ids = NIL;
+	subroot->multiexpr_params = NIL;
+	subroot->eq_classes = NIL;
+	subroot->ec_merging_done = false;
+	subroot->all_result_relids = NULL;
+	subroot->leaf_result_relids = NULL;
+	subroot->append_rel_list = NIL;
+	subroot->row_identity_vars = NIL;
+	subroot->rowMarks = NIL;
+	memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels));
+	memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets));
+	subroot->processed_tlist = NIL;
+	subroot->update_colnos = NIL;
+	subroot->grouping_map = NULL;
+	subroot->minmax_aggs = NIL;
+	subroot->qual_security_level = 0;
+	subroot->hasRecursion = false;
+	subroot->wt_param_id = -1;
+	subroot->non_recursive_path = NULL;
+
+	/* No CTEs to worry about */
+	Assert(subquery->cteList == NIL);
+
+	/*
+	 * If the FROM clause is empty, replace it with a dummy RTE_RESULT RTE, so
+	 * that we don't need so many special cases to deal with that situation.
+	 */
+	replace_empty_jointree(subquery);
+
+	/*
+	 * Pull up any SubLinks within the subquery's quals, so that we don't
+	 * leave unoptimized SubLinks behind.
+	 */
+	if (subquery->hasSubLinks)
+		pull_up_sublinks(subroot);
+
+	/*
+	 * Similarly, preprocess its function RTEs to inline any set-returning
+	 * functions in its rangetable.
+	 */
+	preprocess_function_rtes(subroot);
+
+	/*
+	 * Recursively pull up the subquery's subqueries, so that
+	 * pull_up_subqueries' processing is complete for its jointree and
+	 * rangetable.
+	 *
+	 * Note: it's okay that the subquery's recursion starts with NULL for
+	 * containing-join info, even if we are within an outer join in the upper
+	 * query; the lower query starts with a clean slate for outer-join
+	 * semantics.  Likewise, we needn't pass down appendrel state.
+	 */
+	pull_up_subqueries(subroot);
+
+	/*
+	 * Now we must recheck whether the subquery is still simple enough to pull
+	 * up.  If not, abandon processing it.
+	 *
+	 * We don't really need to recheck all the conditions involved, but it's
+	 * easier just to keep this "if" looking the same as the one in
+	 * pull_up_subqueries_recurse.
+	 */
+	if (is_simple_subquery(root, subquery, rte, lowest_outer_join) &&
+		(containing_appendrel == NULL || is_safe_append_member(subquery)))
+	{
+		/* good to go */
+	}
+	else
+	{
+		/*
+		 * Give up, return unmodified RangeTblRef.
+		 *
+		 * Note: The work we just did will be redone when the subquery gets
+		 * planned on its own.  Perhaps we could avoid that by storing the
+		 * modified subquery back into the rangetable, but I'm not gonna risk
+		 * it now.
+		 */
+		return jtnode;
+	}
+
+	/*
+	 * We must flatten any join alias Vars in the subquery's targetlist,
+	 * because pulling up the subquery's subqueries might have changed their
+	 * expansions into arbitrary expressions, which could affect
+	 * pullup_replace_vars' decisions about whether PlaceHolderVar wrappers
+	 * are needed for tlist entries.  (Likely it'd be better to do
+	 * flatten_join_alias_vars on the whole query tree at some earlier stage,
+	 * maybe even in the rewriter; but for now let's just fix this case here.)
+	 */
+	subquery->targetList = (List *)
+		flatten_join_alias_vars(subroot->parse, (Node *) subquery->targetList);
+
+	/*
+	 * Adjust level-0 varnos in subquery so that we can append its rangetable
+	 * to upper query's.  We have to fix the subquery's append_rel_list as
+	 * well.
+	 */
+	rtoffset = list_length(parse->rtable);
+	OffsetVarNodes((Node *) subquery, rtoffset, 0);
+	OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0);
+
+	/*
+	 * Upper-level vars in subquery are now one level closer to their parent
+	 * than before.
+	 */
+	IncrementVarSublevelsUp((Node *) subquery, -1, 1);
+	IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1);
+
+	/*
+	 * The subquery's targetlist items are now in the appropriate form to
+	 * insert into the top query, except that we may need to wrap them in
+	 * PlaceHolderVars.  Set up required context data for pullup_replace_vars.
+	 */
+	rvcontext.root = root;
+	rvcontext.targetlist = subquery->targetList;
+	rvcontext.target_rte = rte;
+	if (rte->lateral)
+		rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree,
+												  true);
+	else						/* won't need relids */
+		rvcontext.relids = NULL;
+	rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
+	rvcontext.varno = varno;
+	/* these flags will be set below, if needed */
+	rvcontext.need_phvs = false;
+	rvcontext.wrap_non_vars = false;
+	/* initialize cache array with indexes 0 .. length(tlist) */
+	rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) *
+								 sizeof(Node *));
+
+	/*
+	 * If we are under an outer join then non-nullable items and lateral
+	 * references may have to be turned into PlaceHolderVars.
+	 */
+	if (lowest_nulling_outer_join != NULL)
+		rvcontext.need_phvs = true;
+
+	/*
+	 * If we are dealing with an appendrel member then anything that's not a
+	 * simple Var has to be turned into a PlaceHolderVar.  We force this to
+	 * ensure that what we pull up doesn't get merged into a surrounding
+	 * expression during later processing and then fail to match the
+	 * expression actually available from the appendrel.
+	 */
+	if (containing_appendrel != NULL)
+	{
+		rvcontext.need_phvs = true;
+		rvcontext.wrap_non_vars = true;
+	}
+
+	/*
+	 * If the parent query uses grouping sets, we need a PlaceHolderVar for
+	 * anything that's not a simple Var.  Again, this ensures that expressions
+	 * retain their separate identity so that they will match grouping set
+	 * columns when appropriate.  (It'd be sufficient to wrap values used in
+	 * grouping set columns, and do so only in non-aggregated portions of the
+	 * tlist and havingQual, but that would require a lot of infrastructure
+	 * that pullup_replace_vars hasn't currently got.)
+	 */
+	if (parse->groupingSets)
+	{
+		rvcontext.need_phvs = true;
+		rvcontext.wrap_non_vars = true;
+	}
+
+	/*
+	 * Replace all of the top query's references to the subquery's outputs
+	 * with copies of the adjusted subtlist items, being careful not to
+	 * replace any of the jointree structure.
+	 */
+	perform_pullup_replace_vars(root, &rvcontext,
+								lowest_nulling_outer_join,
+								containing_appendrel);
+
+	/*
+	 * If the subquery had a LATERAL marker, propagate that to any of its
+	 * child RTEs that could possibly now contain lateral cross-references.
+	 * The children might or might not contain any actual lateral
+	 * cross-references, but we have to mark the pulled-up child RTEs so that
+	 * later planner stages will check for such.
+	 */
+	if (rte->lateral)
+	{
+		foreach(lc, subquery->rtable)
+		{
+			RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(lc);
+
+			switch (child_rte->rtekind)
+			{
+				case RTE_RELATION:
+					if (child_rte->tablesample)
+						child_rte->lateral = true;
+					break;
+				case RTE_SUBQUERY:
+				case RTE_FUNCTION:
+				case RTE_VALUES:
+				case RTE_TABLEFUNC:
+					child_rte->lateral = true;
+					break;
+				case RTE_JOIN:
+				case RTE_CTE:
+				case RTE_NAMEDTUPLESTORE:
+				case RTE_RESULT:
+					/* these can't contain any lateral references */
+					break;
+			}
+		}
+	}
+
+	/*
+	 * Now append the adjusted rtable entries to upper query. (We hold off
+	 * until after fixing the upper rtable entries; no point in running that
+	 * code on the subquery ones too.)
+	 */
+	parse->rtable = list_concat(parse->rtable, subquery->rtable);
+
+	/*
+	 * Pull up any FOR UPDATE/SHARE markers, too.  (OffsetVarNodes already
+	 * adjusted the marker rtindexes, so just concat the lists.)
+	 */
+	parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks);
+
+	/*
+	 * We also have to fix the relid sets of any PlaceHolderVar nodes in the
+	 * parent query.  (This could perhaps be done by pullup_replace_vars(),
+	 * but it seems cleaner to use two passes.)  Note in particular that any
+	 * PlaceHolderVar nodes just created by pullup_replace_vars() will be
+	 * adjusted, so having created them with the subquery's varno is correct.
+	 *
+	 * Likewise, relids appearing in AppendRelInfo nodes have to be fixed. We
+	 * already checked that this won't require introducing multiple subrelids
+	 * into the single-slot AppendRelInfo structs.
+	 */
+	if (parse->hasSubLinks || root->glob->lastPHId != 0 ||
+		root->append_rel_list)
+	{
+		Relids		subrelids;
+
+		subrelids = get_relids_in_jointree((Node *) subquery->jointree, false);
+		substitute_phv_relids((Node *) parse, varno, subrelids);
+		fix_append_rel_relids(root->append_rel_list, varno, subrelids);
+	}
+
+	/*
+	 * And now add subquery's AppendRelInfos to our list.
+	 */
+	root->append_rel_list = list_concat(root->append_rel_list,
+										subroot->append_rel_list);
+
+	/*
+	 * We don't have to do the equivalent bookkeeping for outer-join info,
+	 * because that hasn't been set up yet.  placeholder_list likewise.
+	 */
+	Assert(root->join_info_list == NIL);
+	Assert(subroot->join_info_list == NIL);
+	Assert(root->placeholder_list == NIL);
+	Assert(subroot->placeholder_list == NIL);
+
+	/*
+	 * Miscellaneous housekeeping.
+	 *
+	 * Although replace_rte_variables() faithfully updated parse->hasSubLinks
+	 * if it copied any SubLinks out of the subquery's targetlist, we still
+	 * could have SubLinks added to the query in the expressions of FUNCTION
+	 * and VALUES RTEs copied up from the subquery.  So it's necessary to copy
+	 * subquery->hasSubLinks anyway.  Perhaps this can be improved someday.
+	 */
+	parse->hasSubLinks |= subquery->hasSubLinks;
+
+	/* If subquery had any RLS conditions, now main query does too */
+	parse->hasRowSecurity |= subquery->hasRowSecurity;
+
+	/*
+	 * subquery won't be pulled up if it hasAggs, hasWindowFuncs, or
+	 * hasTargetSRFs, so no work needed on those flags
+	 */
+
+	/*
+	 * Return the adjusted subquery jointree to replace the RangeTblRef entry
+	 * in parent's jointree; or, if the FromExpr is degenerate, just return
+	 * its single member.
+	 */
+	Assert(IsA(subquery->jointree, FromExpr));
+	Assert(subquery->jointree->fromlist != NIL);
+	if (subquery->jointree->quals == NULL &&
+		list_length(subquery->jointree->fromlist) == 1)
+		return (Node *) linitial(subquery->jointree->fromlist);
+
+	return (Node *) subquery->jointree;
+}
+
+/*
+ * pull_up_simple_union_all
+ *		Pull up a single simple UNION ALL subquery.
+ *
+ * jtnode is a RangeTblRef that has been identified as a simple UNION ALL
+ * subquery by pull_up_subqueries.  We pull up the leaf subqueries and
+ * build an "append relation" for the union set.  The result value is just
+ * jtnode, since we don't actually need to change the query jointree.
+ */
+static Node *
+pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
+{
+	int			varno = ((RangeTblRef *) jtnode)->rtindex;
+	Query	   *subquery = rte->subquery;
+	int			rtoffset = list_length(root->parse->rtable);
+	List	   *rtable;
+
+	/*
+	 * Make a modifiable copy of the subquery's rtable, so we can adjust
+	 * upper-level Vars in it.  There are no such Vars in the setOperations
+	 * tree proper, so fixing the rtable should be sufficient.
+	 */
+	rtable = copyObject(subquery->rtable);
+
+	/*
+	 * Upper-level vars in subquery are now one level closer to their parent
+	 * than before.  We don't have to worry about offsetting varnos, though,
+	 * because the UNION leaf queries can't cross-reference each other.
+	 */
+	IncrementVarSublevelsUp_rtable(rtable, -1, 1);
+
+	/*
+	 * If the UNION ALL subquery had a LATERAL marker, propagate that to all
+	 * its children.  The individual children might or might not contain any
+	 * actual lateral cross-references, but we have to mark the pulled-up
+	 * child RTEs so that later planner stages will check for such.
+	 */
+	if (rte->lateral)
+	{
+		ListCell   *rt;
+
+		foreach(rt, rtable)
+		{
+			RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(rt);
+
+			Assert(child_rte->rtekind == RTE_SUBQUERY);
+			child_rte->lateral = true;
+		}
+	}
+
+	/*
+	 * Append child RTEs to parent rtable.
+	 */
+	root->parse->rtable = list_concat(root->parse->rtable, rtable);
+
+	/*
+	 * Recursively scan the subquery's setOperations tree and add
+	 * AppendRelInfo nodes for leaf subqueries to the parent's
+	 * append_rel_list.  Also apply pull_up_subqueries to the leaf subqueries.
+	 */
+	Assert(subquery->setOperations);
+	pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery,
+							   rtoffset);
+
+	/*
+	 * Mark the parent as an append relation.
+	 */
+	rte->inh = true;
+
+	return jtnode;
+}
+
+/*
+ * pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all
+ *
+ * Build an AppendRelInfo for each leaf query in the setop tree, and then
+ * apply pull_up_subqueries to the leaf query.
+ *
+ * Note that setOpQuery is the Query containing the setOp node, whose tlist
+ * contains references to all the setop output columns.  When called from
+ * pull_up_simple_union_all, this is *not* the same as root->parse, which is
+ * the parent Query we are pulling up into.
+ *
+ * parentRTindex is the appendrel parent's index in root->parse->rtable.
+ *
+ * The child RTEs have already been copied to the parent.  childRToffset
+ * tells us where in the parent's range table they were copied.  When called
+ * from flatten_simple_union_all, childRToffset is 0 since the child RTEs
+ * were already in root->parse->rtable and no RT index adjustment is needed.
+ */
+static void
+pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
+						   Query *setOpQuery, int childRToffset)
+{
+	if (IsA(setOp, RangeTblRef))
+	{
+		RangeTblRef *rtr = (RangeTblRef *) setOp;
+		int			childRTindex;
+		AppendRelInfo *appinfo;
+
+		/*
+		 * Calculate the index in the parent's range table
+		 */
+		childRTindex = childRToffset + rtr->rtindex;
+
+		/*
+		 * Build a suitable AppendRelInfo, and attach to parent's list.
+		 */
+		appinfo = makeNode(AppendRelInfo);
+		appinfo->parent_relid = parentRTindex;
+		appinfo->child_relid = childRTindex;
+		appinfo->parent_reltype = InvalidOid;
+		appinfo->child_reltype = InvalidOid;
+		make_setop_translation_list(setOpQuery, childRTindex, appinfo);
+		appinfo->parent_reloid = InvalidOid;
+		root->append_rel_list = lappend(root->append_rel_list, appinfo);
+
+		/*
+		 * Recursively apply pull_up_subqueries to the new child RTE.  (We
+		 * must build the AppendRelInfo first, because this will modify it.)
+		 * Note that we can pass NULL for containing-join info even if we're
+		 * actually under an outer join, because the child's expressions
+		 * aren't going to propagate up to the join.  Also, we ignore the
+		 * possibility that pull_up_subqueries_recurse() returns a different
+		 * jointree node than what we pass it; if it does, the important thing
+		 * is that it replaced the child relid in the AppendRelInfo node.
+		 */
+		rtr = makeNode(RangeTblRef);
+		rtr->rtindex = childRTindex;
+		(void) pull_up_subqueries_recurse(root, (Node *) rtr,
+										  NULL, NULL, appinfo);
+	}
+	else if (IsA(setOp, SetOperationStmt))
+	{
+		SetOperationStmt *op = (SetOperationStmt *) setOp;
+
+		/* Recurse to reach leaf queries */
+		pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery,
+								   childRToffset);
+		pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery,
+								   childRToffset);
+	}
+	else
+	{
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(setOp));
+	}
+}
+
+/*
+ * make_setop_translation_list
+ *	  Build the list of translations from parent Vars to child Vars for
+ *	  a UNION ALL member.  (At this point it's just a simple list of
+ *	  referencing Vars, but if we succeed in pulling up the member
+ *	  subquery, the Vars will get replaced by pulled-up expressions.)
+ *	  Also create the rather trivial reverse-translation array.
+ */
+static void
+make_setop_translation_list(Query *query, Index newvarno,
+							AppendRelInfo *appinfo)
+{
+	List	   *vars = NIL;
+	AttrNumber *pcolnos;
+	ListCell   *l;
+
+	/* Initialize reverse-translation array with all entries zero */
+	/* (entries for resjunk columns will stay that way) */
+	appinfo->num_child_cols = list_length(query->targetList);
+	appinfo->parent_colnos = pcolnos =
+		(AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber));
+
+	foreach(l, query->targetList)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+		if (tle->resjunk)
+			continue;
+
+		vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
+		pcolnos[tle->resno - 1] = tle->resno;
+	}
+
+	appinfo->translated_vars = vars;
+}
+
+/*
+ * is_simple_subquery
+ *	  Check a subquery in the range table to see if it's simple enough
+ *	  to pull up into the parent query.
+ *
+ * rte is the RTE_SUBQUERY RangeTblEntry that contained the subquery.
+ * (Note subquery is not necessarily equal to rte->subquery; it could be a
+ * processed copy of that.)
+ * lowest_outer_join is the lowest outer join above the subquery, or NULL.
+ */
+static bool
+is_simple_subquery(PlannerInfo *root, Query *subquery, RangeTblEntry *rte,
+				   JoinExpr *lowest_outer_join)
+{
+	/*
+	 * Let's just make sure it's a valid subselect ...
+	 */
+	if (!IsA(subquery, Query) ||
+		subquery->commandType != CMD_SELECT)
+		elog(ERROR, "subquery is bogus");
+
+	/*
+	 * Can't currently pull up a query with setops (unless it's simple UNION
+	 * ALL, which is handled by a different code path). Maybe after querytree
+	 * redesign...
+	 */
+	if (subquery->setOperations)
+		return false;
+
+	/*
+	 * Can't pull up a subquery involving grouping, aggregation, SRFs,
+	 * sorting, limiting, or WITH.  (XXX WITH could possibly be allowed later)
+	 *
+	 * We also don't pull up a subquery that has explicit FOR UPDATE/SHARE
+	 * clauses, because pullup would cause the locking to occur semantically
+	 * higher than it should.  Implicit FOR UPDATE/SHARE is okay because in
+	 * that case the locking was originally declared in the upper query
+	 * anyway.
+	 */
+	if (subquery->hasAggs ||
+		subquery->hasWindowFuncs ||
+		subquery->hasTargetSRFs ||
+		subquery->groupClause ||
+		subquery->groupingSets ||
+		subquery->havingQual ||
+		subquery->sortClause ||
+		subquery->distinctClause ||
+		subquery->limitOffset ||
+		subquery->limitCount ||
+		subquery->hasForUpdate ||
+		subquery->cteList)
+		return false;
+
+	/*
+	 * Don't pull up if the RTE represents a security-barrier view; we
+	 * couldn't prevent information leakage once the RTE's Vars are scattered
+	 * about in the upper query.
+	 */
+	if (rte->security_barrier)
+		return false;
+
+	/*
+	 * If the subquery is LATERAL, check for pullup restrictions from that.
+	 */
+	if (rte->lateral)
+	{
+		bool		restricted;
+		Relids		safe_upper_varnos;
+
+		/*
+		 * The subquery's WHERE and JOIN/ON quals mustn't contain any lateral
+		 * references to rels outside a higher outer join (including the case
+		 * where the outer join is within the subquery itself).  In such a
+		 * case, pulling up would result in a situation where we need to
+		 * postpone quals from below an outer join to above it, which is
+		 * probably completely wrong and in any case is a complication that
+		 * doesn't seem worth addressing at the moment.
+		 */
+		if (lowest_outer_join != NULL)
+		{
+			restricted = true;
+			safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join,
+													   true);
+		}
+		else
+		{
+			restricted = false;
+			safe_upper_varnos = NULL;	/* doesn't matter */
+		}
+
+		if (jointree_contains_lateral_outer_refs(root,
+												 (Node *) subquery->jointree,
+												 restricted, safe_upper_varnos))
+			return false;
+
+		/*
+		 * If there's an outer join above the LATERAL subquery, also disallow
+		 * pullup if the subquery's targetlist has any references to rels
+		 * outside the outer join, since these might get pulled into quals
+		 * above the subquery (but in or below the outer join) and then lead
+		 * to qual-postponement issues similar to the case checked for above.
+		 * (We wouldn't need to prevent pullup if no such references appear in
+		 * outer-query quals, but we don't have enough info here to check
+		 * that.  Also, maybe this restriction could be removed if we forced
+		 * such refs to be wrapped in PlaceHolderVars, even when they're below
+		 * the nearest outer join?	But it's a pretty hokey usage, so not
+		 * clear this is worth sweating over.)
+		 */
+		if (lowest_outer_join != NULL)
+		{
+			Relids		lvarnos = pull_varnos_of_level(root,
+													   (Node *) subquery->targetList,
+													   1);
+
+			if (!bms_is_subset(lvarnos, safe_upper_varnos))
+				return false;
+		}
+	}
+
+	/*
+	 * Don't pull up a subquery that has any volatile functions in its
+	 * targetlist.  Otherwise we might introduce multiple evaluations of these
+	 * functions, if they get copied to multiple places in the upper query,
+	 * leading to surprising results.  (Note: the PlaceHolderVar mechanism
+	 * doesn't quite guarantee single evaluation; else we could pull up anyway
+	 * and just wrap such items in PlaceHolderVars ...)
+	 */
+	if (contain_volatile_functions((Node *) subquery->targetList))
+		return false;
+
+	return true;
+}
+
+/*
+ * pull_up_simple_values
+ *		Pull up a single simple VALUES RTE.
+ *
+ * jtnode is a RangeTblRef that has been identified as a simple VALUES RTE
+ * by pull_up_subqueries.  We always return a RangeTblRef representing a
+ * RESULT RTE to replace it (all failure cases should have been detected by
+ * is_simple_values()).  Actually, what we return is just jtnode, because
+ * we replace the VALUES RTE in the rangetable with the RESULT RTE.
+ *
+ * rte is the RangeTblEntry referenced by jtnode.  Because of the limited
+ * possible usage of VALUES RTEs, we do not need the remaining parameters
+ * of pull_up_subqueries_recurse.
+ */
+static Node *
+pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
+{
+	Query	   *parse = root->parse;
+	int			varno = ((RangeTblRef *) jtnode)->rtindex;
+	List	   *values_list;
+	List	   *tlist;
+	AttrNumber	attrno;
+	pullup_replace_vars_context rvcontext;
+	ListCell   *lc;
+
+	Assert(rte->rtekind == RTE_VALUES);
+	Assert(list_length(rte->values_lists) == 1);
+
+	/*
+	 * Need a modifiable copy of the VALUES list to hack on, just in case it's
+	 * multiply referenced.
+	 */
+	values_list = copyObject(linitial(rte->values_lists));
+
+	/*
+	 * The VALUES RTE can't contain any Vars of level zero, let alone any that
+	 * are join aliases, so no need to flatten join alias Vars.
+	 */
+	Assert(!contain_vars_of_level((Node *) values_list, 0));
+
+	/*
+	 * Set up required context data for pullup_replace_vars.  In particular,
+	 * we have to make the VALUES list look like a subquery targetlist.
+	 */
+	tlist = NIL;
+	attrno = 1;
+	foreach(lc, values_list)
+	{
+		tlist = lappend(tlist,
+						makeTargetEntry((Expr *) lfirst(lc),
+										attrno,
+										NULL,
+										false));
+		attrno++;
+	}
+	rvcontext.root = root;
+	rvcontext.targetlist = tlist;
+	rvcontext.target_rte = rte;
+	rvcontext.relids = NULL;
+	rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
+	rvcontext.varno = varno;
+	rvcontext.need_phvs = false;
+	rvcontext.wrap_non_vars = false;
+	/* initialize cache array with indexes 0 .. length(tlist) */
+	rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
+								 sizeof(Node *));
+
+	/*
+	 * Replace all of the top query's references to the RTE's outputs with
+	 * copies of the adjusted VALUES expressions, being careful not to replace
+	 * any of the jointree structure.  We can assume there's no outer joins or
+	 * appendrels in the dummy Query that surrounds a VALUES RTE.
+	 */
+	perform_pullup_replace_vars(root, &rvcontext, NULL, NULL);
+
+	/*
+	 * There should be no appendrels to fix, nor any outer joins and hence no
+	 * PlaceHolderVars.
+	 */
+	Assert(root->append_rel_list == NIL);
+	Assert(root->join_info_list == NIL);
+	Assert(root->placeholder_list == NIL);
+
+	/*
+	 * Replace the VALUES RTE with a RESULT RTE.  The VALUES RTE is the only
+	 * rtable entry in the current query level, so this is easy.
+	 */
+	Assert(list_length(parse->rtable) == 1);
+
+	/* Create suitable RTE */
+	rte = makeNode(RangeTblEntry);
+	rte->rtekind = RTE_RESULT;
+	rte->eref = makeAlias("*RESULT*", NIL);
+
+	/* Replace rangetable */
+	parse->rtable = list_make1(rte);
+
+	/* We could manufacture a new RangeTblRef, but the one we have is fine */
+	Assert(varno == 1);
+
+	return jtnode;
+}
+
+/*
+ * is_simple_values
+ *	  Check a VALUES RTE in the range table to see if it's simple enough
+ *	  to pull up into the parent query.
+ *
+ * rte is the RTE_VALUES RangeTblEntry to check.
+ */
+static bool
+is_simple_values(PlannerInfo *root, RangeTblEntry *rte)
+{
+	Assert(rte->rtekind == RTE_VALUES);
+
+	/*
+	 * There must be exactly one VALUES list, else it's not semantically
+	 * correct to replace the VALUES RTE with a RESULT RTE, nor would we have
+	 * a unique set of expressions to substitute into the parent query.
+	 */
+	if (list_length(rte->values_lists) != 1)
+		return false;
+
+	/*
+	 * Because VALUES can't appear under an outer join (or at least, we won't
+	 * try to pull it up if it does), we need not worry about LATERAL, nor
+	 * about validity of PHVs for the VALUES' outputs.
+	 */
+
+	/*
+	 * Don't pull up a VALUES that contains any set-returning or volatile
+	 * functions.  The considerations here are basically identical to the
+	 * restrictions on a pull-able subquery's targetlist.
+	 */
+	if (expression_returns_set((Node *) rte->values_lists) ||
+		contain_volatile_functions((Node *) rte->values_lists))
+		return false;
+
+	/*
+	 * Do not pull up a VALUES that's not the only RTE in its parent query.
+	 * This is actually the only case that the parser will generate at the
+	 * moment, and assuming this is true greatly simplifies
+	 * pull_up_simple_values().
+	 */
+	if (list_length(root->parse->rtable) != 1 ||
+		rte != (RangeTblEntry *) linitial(root->parse->rtable))
+		return false;
+
+	return true;
+}
+
+/*
+ * pull_up_constant_function
+ *		Pull up an RTE_FUNCTION expression that was simplified to a constant.
+ *
+ * jtnode is a RangeTblRef that has been identified as a FUNCTION RTE by
+ * pull_up_subqueries.  If its expression is just a Const, hoist that value
+ * up into the parent query, and replace the RTE_FUNCTION with RTE_RESULT.
+ *
+ * In principle we could pull up any immutable expression, but we don't.
+ * That might result in multiple evaluations of the expression, which could
+ * be costly if it's not just a Const.  Also, the main value of this is
+ * to let the constant participate in further const-folding, and of course
+ * that won't happen for a non-Const.
+ *
+ * The pulled-up value might need to be wrapped in a PlaceHolderVar if the
+ * RTE is below an outer join or is part of an appendrel; the extra
+ * parameters show whether that's needed.
+ */
+static Node *
+pull_up_constant_function(PlannerInfo *root, Node *jtnode,
+						  RangeTblEntry *rte,
+						  JoinExpr *lowest_nulling_outer_join,
+						  AppendRelInfo *containing_appendrel)
+{
+	Query	   *parse = root->parse;
+	RangeTblFunction *rtf;
+	TypeFuncClass functypclass;
+	Oid			funcrettype;
+	TupleDesc	tupdesc;
+	pullup_replace_vars_context rvcontext;
+
+	/* Fail if the RTE has ORDINALITY - we don't implement that here. */
+	if (rte->funcordinality)
+		return jtnode;
+
+	/* Fail if RTE isn't a single, simple Const expr */
+	if (list_length(rte->functions) != 1)
+		return jtnode;
+	rtf = linitial_node(RangeTblFunction, rte->functions);
+	if (!IsA(rtf->funcexpr, Const))
+		return jtnode;
+
+	/*
+	 * If the function's result is not a scalar, we punt.  In principle we
+	 * could break the composite constant value apart into per-column
+	 * constants, but for now it seems not worth the work.
+	 */
+	if (rtf->funccolcount != 1)
+		return jtnode;			/* definitely composite */
+
+	functypclass = get_expr_result_type(rtf->funcexpr,
+										&funcrettype,
+										&tupdesc);
+	if (functypclass != TYPEFUNC_SCALAR)
+		return jtnode;			/* must be a one-column composite type */
+
+	/* Create context for applying pullup_replace_vars */
+	rvcontext.root = root;
+	rvcontext.targetlist = list_make1(makeTargetEntry((Expr *) rtf->funcexpr,
+													  1,	/* resno */
+													  NULL, /* resname */
+													  false));	/* resjunk */
+	rvcontext.target_rte = rte;
+
+	/*
+	 * Since this function was reduced to a Const, it doesn't contain any
+	 * lateral references, even if it's marked as LATERAL.  This means we
+	 * don't need to fill relids.
+	 */
+	rvcontext.relids = NULL;
+
+	rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
+	rvcontext.varno = ((RangeTblRef *) jtnode)->rtindex;
+	/* these flags will be set below, if needed */
+	rvcontext.need_phvs = false;
+	rvcontext.wrap_non_vars = false;
+	/* initialize cache array with indexes 0 .. length(tlist) */
+	rvcontext.rv_cache = palloc0((list_length(rvcontext.targetlist) + 1) *
+								 sizeof(Node *));
+
+	/*
+	 * If we are under an outer join then non-nullable items and lateral
+	 * references may have to be turned into PlaceHolderVars.
+	 */
+	if (lowest_nulling_outer_join != NULL)
+		rvcontext.need_phvs = true;
+
+	/*
+	 * If we are dealing with an appendrel member then anything that's not a
+	 * simple Var has to be turned into a PlaceHolderVar.  (See comments in
+	 * pull_up_simple_subquery().)
+	 */
+	if (containing_appendrel != NULL)
+	{
+		rvcontext.need_phvs = true;
+		rvcontext.wrap_non_vars = true;
+	}
+
+	/*
+	 * If the parent query uses grouping sets, we need a PlaceHolderVar for
+	 * anything that's not a simple Var.
+	 */
+	if (parse->groupingSets)
+	{
+		rvcontext.need_phvs = true;
+		rvcontext.wrap_non_vars = true;
+	}
+
+	/*
+	 * Replace all of the top query's references to the RTE's output with
+	 * copies of the funcexpr, being careful not to replace any of the
+	 * jointree structure.
+	 */
+	perform_pullup_replace_vars(root, &rvcontext,
+								lowest_nulling_outer_join,
+								containing_appendrel);
+
+	/*
+	 * We don't need to bother with changing PlaceHolderVars in the parent
+	 * query.  Their references to the RT index are still good for now, and
+	 * will get removed later if we're able to drop the RTE_RESULT.
+	 */
+
+	/*
+	 * Convert the RTE to be RTE_RESULT type, signifying that we don't need to
+	 * scan it anymore, and zero out RTE_FUNCTION-specific fields.  Also make
+	 * sure the RTE is not marked LATERAL, since elsewhere we don't expect
+	 * RTE_RESULTs to be LATERAL.
+	 */
+	rte->rtekind = RTE_RESULT;
+	rte->functions = NIL;
+	rte->lateral = false;
+
+	/*
+	 * We can reuse the RangeTblRef node.
+	 */
+	return jtnode;
+}
+
+/*
+ * is_simple_union_all
+ *	  Check a subquery to see if it's a simple UNION ALL.
+ *
+ * We require all the setops to be UNION ALL (no mixing) and there can't be
+ * any datatype coercions involved, ie, all the leaf queries must emit the
+ * same datatypes.
+ */
+static bool
+is_simple_union_all(Query *subquery)
+{
+	SetOperationStmt *topop;
+
+	/* Let's just make sure it's a valid subselect ... */
+	if (!IsA(subquery, Query) ||
+		subquery->commandType != CMD_SELECT)
+		elog(ERROR, "subquery is bogus");
+
+	/* Is it a set-operation query at all? */
+	topop = castNode(SetOperationStmt, subquery->setOperations);
+	if (!topop)
+		return false;
+
+	/* Can't handle ORDER BY, LIMIT/OFFSET, locking, or WITH */
+	if (subquery->sortClause ||
+		subquery->limitOffset ||
+		subquery->limitCount ||
+		subquery->rowMarks ||
+		subquery->cteList)
+		return false;
+
+	/* Recursively check the tree of set operations */
+	return is_simple_union_all_recurse((Node *) topop, subquery,
+									   topop->colTypes);
+}
+
+static bool
+is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
+{
+	if (IsA(setOp, RangeTblRef))
+	{
+		RangeTblRef *rtr = (RangeTblRef *) setOp;
+		RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable);
+		Query	   *subquery = rte->subquery;
+
+		Assert(subquery != NULL);
+
+		/* Leaf nodes are OK if they match the toplevel column types */
+		/* We don't have to compare typmods or collations here */
+		return tlist_same_datatypes(subquery->targetList, colTypes, true);
+	}
+	else if (IsA(setOp, SetOperationStmt))
+	{
+		SetOperationStmt *op = (SetOperationStmt *) setOp;
+
+		/* Must be UNION ALL */
+		if (op->op != SETOP_UNION || !op->all)
+			return false;
+
+		/* Recurse to check inputs */
+		return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) &&
+			is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes);
+	}
+	else
+	{
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(setOp));
+		return false;			/* keep compiler quiet */
+	}
+}
+
+/*
+ * is_safe_append_member
+ *	  Check a subquery that is a leaf of a UNION ALL appendrel to see if it's
+ *	  safe to pull up.
+ */
+static bool
+is_safe_append_member(Query *subquery)
+{
+	FromExpr   *jtnode;
+
+	/*
+	 * It's only safe to pull up the child if its jointree contains exactly
+	 * one RTE, else the AppendRelInfo data structure breaks. The one base RTE
+	 * could be buried in several levels of FromExpr, however.  Also, if the
+	 * child's jointree is completely empty, we can pull up because
+	 * pull_up_simple_subquery will insert a single RTE_RESULT RTE instead.
+	 *
+	 * Also, the child can't have any WHERE quals because there's no place to
+	 * put them in an appendrel.  (This is a bit annoying...) If we didn't
+	 * need to check this, we'd just test whether get_relids_in_jointree()
+	 * yields a singleton set, to be more consistent with the coding of
+	 * fix_append_rel_relids().
+	 */
+	jtnode = subquery->jointree;
+	Assert(IsA(jtnode, FromExpr));
+	/* Check the completely-empty case */
+	if (jtnode->fromlist == NIL && jtnode->quals == NULL)
+		return true;
+	/* Check the more general case */
+	while (IsA(jtnode, FromExpr))
+	{
+		if (jtnode->quals != NULL)
+			return false;
+		if (list_length(jtnode->fromlist) != 1)
+			return false;
+		jtnode = linitial(jtnode->fromlist);
+	}
+	if (!IsA(jtnode, RangeTblRef))
+		return false;
+
+	return true;
+}
+
+/*
+ * jointree_contains_lateral_outer_refs
+ *		Check for disallowed lateral references in a jointree's quals
+ *
+ * If restricted is false, all level-1 Vars are allowed (but we still must
+ * search the jointree, since it might contain outer joins below which there
+ * will be restrictions).  If restricted is true, return true when any qual
+ * in the jointree contains level-1 Vars coming from outside the rels listed
+ * in safe_upper_varnos.
+ */
+static bool
+jointree_contains_lateral_outer_refs(PlannerInfo *root, Node *jtnode,
+									 bool restricted,
+									 Relids safe_upper_varnos)
+{
+	if (jtnode == NULL)
+		return false;
+	if (IsA(jtnode, RangeTblRef))
+		return false;
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		/* First, recurse to check child joins */
+		foreach(l, f->fromlist)
+		{
+			if (jointree_contains_lateral_outer_refs(root,
+													 lfirst(l),
+													 restricted,
+													 safe_upper_varnos))
+				return true;
+		}
+
+		/* Then check the top-level quals */
+		if (restricted &&
+			!bms_is_subset(pull_varnos_of_level(root, f->quals, 1),
+						   safe_upper_varnos))
+			return true;
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+
+		/*
+		 * If this is an outer join, we mustn't allow any upper lateral
+		 * references in or below it.
+		 */
+		if (j->jointype != JOIN_INNER)
+		{
+			restricted = true;
+			safe_upper_varnos = NULL;
+		}
+
+		/* Check the child joins */
+		if (jointree_contains_lateral_outer_refs(root,
+												 j->larg,
+												 restricted,
+												 safe_upper_varnos))
+			return true;
+		if (jointree_contains_lateral_outer_refs(root,
+												 j->rarg,
+												 restricted,
+												 safe_upper_varnos))
+			return true;
+
+		/* Check the JOIN's qual clauses */
+		if (restricted &&
+			!bms_is_subset(pull_varnos_of_level(root, j->quals, 1),
+						   safe_upper_varnos))
+			return true;
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return false;
+}
+
+/*
+ * Perform pullup_replace_vars everyplace it's needed in the query tree.
+ *
+ * Caller has already filled *rvcontext with data describing what to
+ * substitute for Vars referencing the target subquery.  In addition
+ * we need the identity of the lowest outer join that can null the
+ * target subquery, and its containing appendrel if any.
+ */
+static void
+perform_pullup_replace_vars(PlannerInfo *root,
+							pullup_replace_vars_context *rvcontext,
+							JoinExpr *lowest_nulling_outer_join,
+							AppendRelInfo *containing_appendrel)
+{
+	Query	   *parse = root->parse;
+	ListCell   *lc;
+
+	/*
+	 * Replace all of the top query's references to the subquery's outputs
+	 * with copies of the adjusted subtlist items, being careful not to
+	 * replace any of the jointree structure.  (This'd be a lot cleaner if we
+	 * could use query_tree_mutator.)  We have to use PHVs in the targetList,
+	 * returningList, and havingQual, since those are certainly above any
+	 * outer join.  replace_vars_in_jointree tracks its location in the
+	 * jointree and uses PHVs or not appropriately.
+	 */
+	parse->targetList = (List *)
+		pullup_replace_vars((Node *) parse->targetList, rvcontext);
+	parse->returningList = (List *)
+		pullup_replace_vars((Node *) parse->returningList, rvcontext);
+	if (parse->onConflict)
+	{
+		parse->onConflict->onConflictSet = (List *)
+			pullup_replace_vars((Node *) parse->onConflict->onConflictSet,
+								rvcontext);
+		parse->onConflict->onConflictWhere =
+			pullup_replace_vars(parse->onConflict->onConflictWhere,
+								rvcontext);
+
+		/*
+		 * We assume ON CONFLICT's arbiterElems, arbiterWhere, exclRelTlist
+		 * can't contain any references to a subquery.
+		 */
+	}
+	replace_vars_in_jointree((Node *) parse->jointree, rvcontext,
+							 lowest_nulling_outer_join);
+	Assert(parse->setOperations == NULL);
+	parse->havingQual = pullup_replace_vars(parse->havingQual, rvcontext);
+
+	/*
+	 * Replace references in the translated_vars lists of appendrels.  When
+	 * pulling up an appendrel member, we do not need PHVs in the list of the
+	 * parent appendrel --- there isn't any outer join between.  Elsewhere,
+	 * use PHVs for safety.  (This analysis could be made tighter but it seems
+	 * unlikely to be worth much trouble.)
+	 */
+	foreach(lc, root->append_rel_list)
+	{
+		AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
+		bool		save_need_phvs = rvcontext->need_phvs;
+
+		if (appinfo == containing_appendrel)
+			rvcontext->need_phvs = false;
+		appinfo->translated_vars = (List *)
+			pullup_replace_vars((Node *) appinfo->translated_vars, rvcontext);
+		rvcontext->need_phvs = save_need_phvs;
+	}
+
+	/*
+	 * Replace references in the joinaliasvars lists of join RTEs.
+	 *
+	 * You might think that we could avoid using PHVs for alias vars of joins
+	 * below lowest_nulling_outer_join, but that doesn't work because the
+	 * alias vars could be referenced above that join; we need the PHVs to be
+	 * present in such references after the alias vars get flattened.  (It
+	 * might be worth trying to be smarter here, someday.)
+	 */
+	foreach(lc, parse->rtable)
+	{
+		RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc);
+
+		if (otherrte->rtekind == RTE_JOIN)
+			otherrte->joinaliasvars = (List *)
+				pullup_replace_vars((Node *) otherrte->joinaliasvars,
+									rvcontext);
+	}
+}
+
+/*
+ * Helper routine for perform_pullup_replace_vars: do pullup_replace_vars on
+ * every expression in the jointree, without changing the jointree structure
+ * itself.  Ugly, but there's no other way...
+ *
+ * If we are at or below lowest_nulling_outer_join, we can suppress use of
+ * PlaceHolderVars wrapped around the replacement expressions.
+ */
+static void
+replace_vars_in_jointree(Node *jtnode,
+						 pullup_replace_vars_context *context,
+						 JoinExpr *lowest_nulling_outer_join)
+{
+	if (jtnode == NULL)
+		return;
+	if (IsA(jtnode, RangeTblRef))
+	{
+		/*
+		 * If the RangeTblRef refers to a LATERAL subquery (that isn't the
+		 * same subquery we're pulling up), it might contain references to the
+		 * target subquery, which we must replace.  We drive this from the
+		 * jointree scan, rather than a scan of the rtable, for a couple of
+		 * reasons: we can avoid processing no-longer-referenced RTEs, and we
+		 * can use the appropriate setting of need_phvs depending on whether
+		 * the RTE is above possibly-nulling outer joins or not.
+		 */
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+
+		if (varno != context->varno)	/* ignore target subquery itself */
+		{
+			RangeTblEntry *rte = rt_fetch(varno, context->root->parse->rtable);
+
+			Assert(rte != context->target_rte);
+			if (rte->lateral)
+			{
+				switch (rte->rtekind)
+				{
+					case RTE_RELATION:
+						/* shouldn't be marked LATERAL unless tablesample */
+						Assert(rte->tablesample);
+						rte->tablesample = (TableSampleClause *)
+							pullup_replace_vars((Node *) rte->tablesample,
+												context);
+						break;
+					case RTE_SUBQUERY:
+						rte->subquery =
+							pullup_replace_vars_subquery(rte->subquery,
+														 context);
+						break;
+					case RTE_FUNCTION:
+						rte->functions = (List *)
+							pullup_replace_vars((Node *) rte->functions,
+												context);
+						break;
+					case RTE_TABLEFUNC:
+						rte->tablefunc = (TableFunc *)
+							pullup_replace_vars((Node *) rte->tablefunc,
+												context);
+						break;
+					case RTE_VALUES:
+						rte->values_lists = (List *)
+							pullup_replace_vars((Node *) rte->values_lists,
+												context);
+						break;
+					case RTE_JOIN:
+					case RTE_CTE:
+					case RTE_NAMEDTUPLESTORE:
+					case RTE_RESULT:
+						/* these shouldn't be marked LATERAL */
+						Assert(false);
+						break;
+				}
+			}
+		}
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		foreach(l, f->fromlist)
+			replace_vars_in_jointree(lfirst(l), context,
+									 lowest_nulling_outer_join);
+		f->quals = pullup_replace_vars(f->quals, context);
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+		bool		save_need_phvs = context->need_phvs;
+
+		if (j == lowest_nulling_outer_join)
+		{
+			/* no more PHVs in or below this join */
+			context->need_phvs = false;
+			lowest_nulling_outer_join = NULL;
+		}
+		replace_vars_in_jointree(j->larg, context, lowest_nulling_outer_join);
+		replace_vars_in_jointree(j->rarg, context, lowest_nulling_outer_join);
+
+		/*
+		 * Use PHVs within the join quals of a full join, even when it's the
+		 * lowest nulling outer join.  Otherwise, we cannot identify which
+		 * side of the join a pulled-up var-free expression came from, which
+		 * can lead to failure to make a plan at all because none of the quals
+		 * appear to be mergeable or hashable conditions.  For this purpose we
+		 * don't care about the state of wrap_non_vars, so leave it alone.
+		 */
+		if (j->jointype == JOIN_FULL)
+			context->need_phvs = true;
+
+		j->quals = pullup_replace_vars(j->quals, context);
+
+		/*
+		 * We don't bother to update the colvars list, since it won't be used
+		 * again ...
+		 */
+		context->need_phvs = save_need_phvs;
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+}
+
+/*
+ * Apply pullup variable replacement throughout an expression tree
+ *
+ * Returns a modified copy of the tree, so this can't be used where we
+ * need to do in-place replacement.
+ */
+static Node *
+pullup_replace_vars(Node *expr, pullup_replace_vars_context *context)
+{
+	return replace_rte_variables(expr,
+								 context->varno, 0,
+								 pullup_replace_vars_callback,
+								 (void *) context,
+								 context->outer_hasSubLinks);
+}
+
+static Node *
+pullup_replace_vars_callback(Var *var,
+							 replace_rte_variables_context *context)
+{
+	pullup_replace_vars_context *rcon = (pullup_replace_vars_context *) context->callback_arg;
+	int			varattno = var->varattno;
+	Node	   *newnode;
+
+	/*
+	 * If PlaceHolderVars are needed, we cache the modified expressions in
+	 * rcon->rv_cache[].  This is not in hopes of any material speed gain
+	 * within this function, but to avoid generating identical PHVs with
+	 * different IDs.  That would result in duplicate evaluations at runtime,
+	 * and possibly prevent optimizations that rely on recognizing different
+	 * references to the same subquery output as being equal().  So it's worth
+	 * a bit of extra effort to avoid it.
+	 */
+	if (rcon->need_phvs &&
+		varattno >= InvalidAttrNumber &&
+		varattno <= list_length(rcon->targetlist) &&
+		rcon->rv_cache[varattno] != NULL)
+	{
+		/* Just copy the entry and fall through to adjust its varlevelsup */
+		newnode = copyObject(rcon->rv_cache[varattno]);
+	}
+	else if (varattno == InvalidAttrNumber)
+	{
+		/* Must expand whole-tuple reference into RowExpr */
+		RowExpr    *rowexpr;
+		List	   *colnames;
+		List	   *fields;
+		bool		save_need_phvs = rcon->need_phvs;
+		int			save_sublevelsup = context->sublevels_up;
+
+		/*
+		 * If generating an expansion for a var of a named rowtype (ie, this
+		 * is a plain relation RTE), then we must include dummy items for
+		 * dropped columns.  If the var is RECORD (ie, this is a JOIN), then
+		 * omit dropped columns. Either way, attach column names to the
+		 * RowExpr for use of ruleutils.c.
+		 *
+		 * In order to be able to cache the results, we always generate the
+		 * expansion with varlevelsup = 0, and then adjust if needed.
+		 */
+		expandRTE(rcon->target_rte,
+				  var->varno, 0 /* not varlevelsup */ , var->location,
+				  (var->vartype != RECORDOID),
+				  &colnames, &fields);
+		/* Adjust the generated per-field Vars, but don't insert PHVs */
+		rcon->need_phvs = false;
+		context->sublevels_up = 0;	/* to match the expandRTE output */
+		fields = (List *) replace_rte_variables_mutator((Node *) fields,
+														context);
+		rcon->need_phvs = save_need_phvs;
+		context->sublevels_up = save_sublevelsup;
+
+		rowexpr = makeNode(RowExpr);
+		rowexpr->args = fields;
+		rowexpr->row_typeid = var->vartype;
+		rowexpr->row_format = COERCE_IMPLICIT_CAST;
+		rowexpr->colnames = colnames;
+		rowexpr->location = var->location;
+		newnode = (Node *) rowexpr;
+
+		/*
+		 * Insert PlaceHolderVar if needed.  Notice that we are wrapping one
+		 * PlaceHolderVar around the whole RowExpr, rather than putting one
+		 * around each element of the row.  This is because we need the
+		 * expression to yield NULL, not ROW(NULL,NULL,...) when it is forced
+		 * to null by an outer join.
+		 */
+		if (rcon->need_phvs)
+		{
+			/* RowExpr is certainly not strict, so always need PHV */
+			newnode = (Node *)
+				make_placeholder_expr(rcon->root,
+									  (Expr *) newnode,
+									  bms_make_singleton(rcon->varno));
+			/* cache it with the PHV, and with varlevelsup still zero */
+			rcon->rv_cache[InvalidAttrNumber] = copyObject(newnode);
+		}
+	}
+	else
+	{
+		/* Normal case referencing one targetlist element */
+		TargetEntry *tle = get_tle_by_resno(rcon->targetlist, varattno);
+
+		if (tle == NULL)		/* shouldn't happen */
+			elog(ERROR, "could not find attribute %d in subquery targetlist",
+				 varattno);
+
+		/* Make a copy of the tlist item to return */
+		newnode = (Node *) copyObject(tle->expr);
+
+		/* Insert PlaceHolderVar if needed */
+		if (rcon->need_phvs)
+		{
+			bool		wrap;
+
+			if (newnode && IsA(newnode, Var) &&
+				((Var *) newnode)->varlevelsup == 0)
+			{
+				/*
+				 * Simple Vars always escape being wrapped, unless they are
+				 * lateral references to something outside the subquery being
+				 * pulled up.  (Even then, we could omit the PlaceHolderVar if
+				 * the referenced rel is under the same lowest outer join, but
+				 * it doesn't seem worth the trouble to check that.)
+				 */
+				if (rcon->target_rte->lateral &&
+					!bms_is_member(((Var *) newnode)->varno, rcon->relids))
+					wrap = true;
+				else
+					wrap = false;
+			}
+			else if (newnode && IsA(newnode, PlaceHolderVar) &&
+					 ((PlaceHolderVar *) newnode)->phlevelsup == 0)
+			{
+				/* No need to wrap a PlaceHolderVar with another one, either */
+				wrap = false;
+			}
+			else if (rcon->wrap_non_vars)
+			{
+				/* Wrap all non-Vars in a PlaceHolderVar */
+				wrap = true;
+			}
+			else
+			{
+				/*
+				 * If it contains a Var of the subquery being pulled up, and
+				 * does not contain any non-strict constructs, then it's
+				 * certainly nullable so we don't need to insert a
+				 * PlaceHolderVar.
+				 *
+				 * This analysis could be tighter: in particular, a non-strict
+				 * construct hidden within a lower-level PlaceHolderVar is not
+				 * reason to add another PHV.  But for now it doesn't seem
+				 * worth the code to be more exact.
+				 *
+				 * Note: in future maybe we should insert a PlaceHolderVar
+				 * anyway, if the tlist item is expensive to evaluate?
+				 *
+				 * For a LATERAL subquery, we have to check the actual var
+				 * membership of the node, but if it's non-lateral then any
+				 * level-zero var must belong to the subquery.
+				 */
+				if ((rcon->target_rte->lateral ?
+					 bms_overlap(pull_varnos(rcon->root, (Node *) newnode),
+								 rcon->relids) :
+					 contain_vars_of_level((Node *) newnode, 0)) &&
+					!contain_nonstrict_functions((Node *) newnode))
+				{
+					/* No wrap needed */
+					wrap = false;
+				}
+				else
+				{
+					/* Else wrap it in a PlaceHolderVar */
+					wrap = true;
+				}
+			}
+
+			if (wrap)
+				newnode = (Node *)
+					make_placeholder_expr(rcon->root,
+										  (Expr *) newnode,
+										  bms_make_singleton(rcon->varno));
+
+			/*
+			 * Cache it if possible (ie, if the attno is in range, which it
+			 * probably always should be).  We can cache the value even if we
+			 * decided we didn't need a PHV, since this result will be
+			 * suitable for any request that has need_phvs.
+			 */
+			if (varattno > InvalidAttrNumber &&
+				varattno <= list_length(rcon->targetlist))
+				rcon->rv_cache[varattno] = copyObject(newnode);
+		}
+	}
+
+	/* Must adjust varlevelsup if tlist item is from higher query */
+	if (var->varlevelsup > 0)
+		IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
+
+	return newnode;
+}
+
+/*
+ * Apply pullup variable replacement to a subquery
+ *
+ * This needs to be different from pullup_replace_vars() because
+ * replace_rte_variables will think that it shouldn't increment sublevels_up
+ * before entering the Query; so we need to call it with sublevels_up == 1.
+ */
+static Query *
+pullup_replace_vars_subquery(Query *query,
+							 pullup_replace_vars_context *context)
+{
+	Assert(IsA(query, Query));
+	return (Query *) replace_rte_variables((Node *) query,
+										   context->varno, 1,
+										   pullup_replace_vars_callback,
+										   (void *) context,
+										   NULL);
+}
+
+
+/*
+ * flatten_simple_union_all
+ *		Try to optimize top-level UNION ALL structure into an appendrel
+ *
+ * If a query's setOperations tree consists entirely of simple UNION ALL
+ * operations, flatten it into an append relation, which we can process more
+ * intelligently than the general setops case.  Otherwise, do nothing.
+ *
+ * In most cases, this can succeed only for a top-level query, because for a
+ * subquery in FROM, the parent query's invocation of pull_up_subqueries would
+ * already have flattened the UNION via pull_up_simple_union_all.  But there
+ * are a few cases we can support here but not in that code path, for example
+ * when the subquery also contains ORDER BY.
+ */
+void
+flatten_simple_union_all(PlannerInfo *root)
+{
+	Query	   *parse = root->parse;
+	SetOperationStmt *topop;
+	Node	   *leftmostjtnode;
+	int			leftmostRTI;
+	RangeTblEntry *leftmostRTE;
+	int			childRTI;
+	RangeTblEntry *childRTE;
+	RangeTblRef *rtr;
+
+	/* Shouldn't be called unless query has setops */
+	topop = castNode(SetOperationStmt, parse->setOperations);
+	Assert(topop);
+
+	/* Can't optimize away a recursive UNION */
+	if (root->hasRecursion)
+		return;
+
+	/*
+	 * Recursively check the tree of set operations.  If not all UNION ALL
+	 * with identical column types, punt.
+	 */
+	if (!is_simple_union_all_recurse((Node *) topop, parse, topop->colTypes))
+		return;
+
+	/*
+	 * Locate the leftmost leaf query in the setops tree.  The upper query's
+	 * Vars all refer to this RTE (see transformSetOperationStmt).
+	 */
+	leftmostjtnode = topop->larg;
+	while (leftmostjtnode && IsA(leftmostjtnode, SetOperationStmt))
+		leftmostjtnode = ((SetOperationStmt *) leftmostjtnode)->larg;
+	Assert(leftmostjtnode && IsA(leftmostjtnode, RangeTblRef));
+	leftmostRTI = ((RangeTblRef *) leftmostjtnode)->rtindex;
+	leftmostRTE = rt_fetch(leftmostRTI, parse->rtable);
+	Assert(leftmostRTE->rtekind == RTE_SUBQUERY);
+
+	/*
+	 * Make a copy of the leftmost RTE and add it to the rtable.  This copy
+	 * will represent the leftmost leaf query in its capacity as a member of
+	 * the appendrel.  The original will represent the appendrel as a whole.
+	 * (We must do things this way because the upper query's Vars have to be
+	 * seen as referring to the whole appendrel.)
+	 */
+	childRTE = copyObject(leftmostRTE);
+	parse->rtable = lappend(parse->rtable, childRTE);
+	childRTI = list_length(parse->rtable);
+
+	/* Modify the setops tree to reference the child copy */
+	((RangeTblRef *) leftmostjtnode)->rtindex = childRTI;
+
+	/* Modify the formerly-leftmost RTE to mark it as an appendrel parent */
+	leftmostRTE->inh = true;
+
+	/*
+	 * Form a RangeTblRef for the appendrel, and insert it into FROM.  The top
+	 * Query of a setops tree should have had an empty FromClause initially.
+	 */
+	rtr = makeNode(RangeTblRef);
+	rtr->rtindex = leftmostRTI;
+	Assert(parse->jointree->fromlist == NIL);
+	parse->jointree->fromlist = list_make1(rtr);
+
+	/*
+	 * Now pretend the query has no setops.  We must do this before trying to
+	 * do subquery pullup, because of Assert in pull_up_simple_subquery.
+	 */
+	parse->setOperations = NULL;
+
+	/*
+	 * Build AppendRelInfo information, and apply pull_up_subqueries to the
+	 * leaf queries of the UNION ALL.  (We must do that now because they
+	 * weren't previously referenced by the jointree, and so were missed by
+	 * the main invocation of pull_up_subqueries.)
+	 */
+	pull_up_union_leaf_queries((Node *) topop, root, leftmostRTI, parse, 0);
+}
+
+
+/*
+ * reduce_outer_joins
+ *		Attempt to reduce outer joins to plain inner joins.
+ *
+ * The idea here is that given a query like
+ *		SELECT ... FROM a LEFT JOIN b ON (...) WHERE b.y = 42;
+ * we can reduce the LEFT JOIN to a plain JOIN if the "=" operator in WHERE
+ * is strict.  The strict operator will always return NULL, causing the outer
+ * WHERE to fail, on any row where the LEFT JOIN filled in NULLs for b's
+ * columns.  Therefore, there's no need for the join to produce null-extended
+ * rows in the first place --- which makes it a plain join not an outer join.
+ * (This scenario may not be very likely in a query written out by hand, but
+ * it's reasonably likely when pushing quals down into complex views.)
+ *
+ * More generally, an outer join can be reduced in strength if there is a
+ * strict qual above it in the qual tree that constrains a Var from the
+ * nullable side of the join to be non-null.  (For FULL joins this applies
+ * to each side separately.)
+ *
+ * Another transformation we apply here is to recognize cases like
+ *		SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL;
+ * If the join clause is strict for b.y, then only null-extended rows could
+ * pass the upper WHERE, and we can conclude that what the query is really
+ * specifying is an anti-semijoin.  We change the join type from JOIN_LEFT
+ * to JOIN_ANTI.  The IS NULL clause then becomes redundant, and must be
+ * removed to prevent bogus selectivity calculations, but we leave it to
+ * distribute_qual_to_rels to get rid of such clauses.
+ *
+ * Also, we get rid of JOIN_RIGHT cases by flipping them around to become
+ * JOIN_LEFT.  This saves some code here and in some later planner routines,
+ * but the main reason to do it is to not need to invent a JOIN_REVERSE_ANTI
+ * join type.
+ *
+ * To ease recognition of strict qual clauses, we require this routine to be
+ * run after expression preprocessing (i.e., qual canonicalization and JOIN
+ * alias-var expansion).
+ */
+void
+reduce_outer_joins(PlannerInfo *root)
+{
+	reduce_outer_joins_state *state;
+
+	/*
+	 * To avoid doing strictness checks on more quals than necessary, we want
+	 * to stop descending the jointree as soon as there are no outer joins
+	 * below our current point.  This consideration forces a two-pass process.
+	 * The first pass gathers information about which base rels appear below
+	 * each side of each join clause, and about whether there are outer
+	 * join(s) below each side of each join clause. The second pass examines
+	 * qual clauses and changes join types as it descends the tree.
+	 */
+	state = reduce_outer_joins_pass1((Node *) root->parse->jointree);
+
+	/* planner.c shouldn't have called me if no outer joins */
+	if (state == NULL || !state->contains_outer)
+		elog(ERROR, "so where are the outer joins?");
+
+	reduce_outer_joins_pass2((Node *) root->parse->jointree,
+							 state, root, NULL, NIL, NIL);
+}
+
+/*
+ * reduce_outer_joins_pass1 - phase 1 data collection
+ *
+ * Returns a state node describing the given jointree node.
+ */
+static reduce_outer_joins_state *
+reduce_outer_joins_pass1(Node *jtnode)
+{
+	reduce_outer_joins_state *result;
+
+	result = (reduce_outer_joins_state *)
+		palloc(sizeof(reduce_outer_joins_state));
+	result->relids = NULL;
+	result->contains_outer = false;
+	result->sub_states = NIL;
+
+	if (jtnode == NULL)
+		return result;
+	if (IsA(jtnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+
+		result->relids = bms_make_singleton(varno);
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		foreach(l, f->fromlist)
+		{
+			reduce_outer_joins_state *sub_state;
+
+			sub_state = reduce_outer_joins_pass1(lfirst(l));
+			result->relids = bms_add_members(result->relids,
+											 sub_state->relids);
+			result->contains_outer |= sub_state->contains_outer;
+			result->sub_states = lappend(result->sub_states, sub_state);
+		}
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+		reduce_outer_joins_state *sub_state;
+
+		/* join's own RT index is not wanted in result->relids */
+		if (IS_OUTER_JOIN(j->jointype))
+			result->contains_outer = true;
+
+		sub_state = reduce_outer_joins_pass1(j->larg);
+		result->relids = bms_add_members(result->relids,
+										 sub_state->relids);
+		result->contains_outer |= sub_state->contains_outer;
+		result->sub_states = lappend(result->sub_states, sub_state);
+
+		sub_state = reduce_outer_joins_pass1(j->rarg);
+		result->relids = bms_add_members(result->relids,
+										 sub_state->relids);
+		result->contains_outer |= sub_state->contains_outer;
+		result->sub_states = lappend(result->sub_states, sub_state);
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return result;
+}
+
+/*
+ * reduce_outer_joins_pass2 - phase 2 processing
+ *
+ *	jtnode: current jointree node
+ *	state: state data collected by phase 1 for this node
+ *	root: toplevel planner state
+ *	nonnullable_rels: set of base relids forced non-null by upper quals
+ *	nonnullable_vars: list of Vars forced non-null by upper quals
+ *	forced_null_vars: list of Vars forced null by upper quals
+ */
+static void
+reduce_outer_joins_pass2(Node *jtnode,
+						 reduce_outer_joins_state *state,
+						 PlannerInfo *root,
+						 Relids nonnullable_rels,
+						 List *nonnullable_vars,
+						 List *forced_null_vars)
+{
+	/*
+	 * pass 2 should never descend as far as an empty subnode or base rel,
+	 * because it's only called on subtrees marked as contains_outer.
+	 */
+	if (jtnode == NULL)
+		elog(ERROR, "reached empty jointree");
+	if (IsA(jtnode, RangeTblRef))
+		elog(ERROR, "reached base rel");
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+		ListCell   *s;
+		Relids		pass_nonnullable_rels;
+		List	   *pass_nonnullable_vars;
+		List	   *pass_forced_null_vars;
+
+		/* Scan quals to see if we can add any constraints */
+		pass_nonnullable_rels = find_nonnullable_rels(f->quals);
+		pass_nonnullable_rels = bms_add_members(pass_nonnullable_rels,
+												nonnullable_rels);
+		pass_nonnullable_vars = find_nonnullable_vars(f->quals);
+		pass_nonnullable_vars = list_concat(pass_nonnullable_vars,
+											nonnullable_vars);
+		pass_forced_null_vars = find_forced_null_vars(f->quals);
+		pass_forced_null_vars = list_concat(pass_forced_null_vars,
+											forced_null_vars);
+		/* And recurse --- but only into interesting subtrees */
+		Assert(list_length(f->fromlist) == list_length(state->sub_states));
+		forboth(l, f->fromlist, s, state->sub_states)
+		{
+			reduce_outer_joins_state *sub_state = lfirst(s);
+
+			if (sub_state->contains_outer)
+				reduce_outer_joins_pass2(lfirst(l), sub_state, root,
+										 pass_nonnullable_rels,
+										 pass_nonnullable_vars,
+										 pass_forced_null_vars);
+		}
+		bms_free(pass_nonnullable_rels);
+		/* can't so easily clean up var lists, unfortunately */
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+		int			rtindex = j->rtindex;
+		JoinType	jointype = j->jointype;
+		reduce_outer_joins_state *left_state = linitial(state->sub_states);
+		reduce_outer_joins_state *right_state = lsecond(state->sub_states);
+		List	   *local_nonnullable_vars = NIL;
+		bool		computed_local_nonnullable_vars = false;
+
+		/* Can we simplify this join? */
+		switch (jointype)
+		{
+			case JOIN_INNER:
+				break;
+			case JOIN_LEFT:
+				if (bms_overlap(nonnullable_rels, right_state->relids))
+					jointype = JOIN_INNER;
+				break;
+			case JOIN_RIGHT:
+				if (bms_overlap(nonnullable_rels, left_state->relids))
+					jointype = JOIN_INNER;
+				break;
+			case JOIN_FULL:
+				if (bms_overlap(nonnullable_rels, left_state->relids))
+				{
+					if (bms_overlap(nonnullable_rels, right_state->relids))
+						jointype = JOIN_INNER;
+					else
+						jointype = JOIN_LEFT;
+				}
+				else
+				{
+					if (bms_overlap(nonnullable_rels, right_state->relids))
+						jointype = JOIN_RIGHT;
+				}
+				break;
+			case JOIN_SEMI:
+			case JOIN_ANTI:
+
+				/*
+				 * These could only have been introduced by pull_up_sublinks,
+				 * so there's no way that upper quals could refer to their
+				 * righthand sides, and no point in checking.
+				 */
+				break;
+			default:
+				elog(ERROR, "unrecognized join type: %d",
+					 (int) jointype);
+				break;
+		}
+
+		/*
+		 * Convert JOIN_RIGHT to JOIN_LEFT.  Note that in the case where we
+		 * reduced JOIN_FULL to JOIN_RIGHT, this will mean the JoinExpr no
+		 * longer matches the internal ordering of any CoalesceExpr's built to
+		 * represent merged join variables.  We don't care about that at
+		 * present, but be wary of it ...
+		 */
+		if (jointype == JOIN_RIGHT)
+		{
+			Node	   *tmparg;
+
+			tmparg = j->larg;
+			j->larg = j->rarg;
+			j->rarg = tmparg;
+			jointype = JOIN_LEFT;
+			right_state = linitial(state->sub_states);
+			left_state = lsecond(state->sub_states);
+		}
+
+		/*
+		 * See if we can reduce JOIN_LEFT to JOIN_ANTI.  This is the case if
+		 * the join's own quals are strict for any var that was forced null by
+		 * higher qual levels.  NOTE: there are other ways that we could
+		 * detect an anti-join, in particular if we were to check whether Vars
+		 * coming from the RHS must be non-null because of table constraints.
+		 * That seems complicated and expensive though (in particular, one
+		 * would have to be wary of lower outer joins). For the moment this
+		 * seems sufficient.
+		 */
+		if (jointype == JOIN_LEFT)
+		{
+			List	   *overlap;
+
+			local_nonnullable_vars = find_nonnullable_vars(j->quals);
+			computed_local_nonnullable_vars = true;
+
+			/*
+			 * It's not sufficient to check whether local_nonnullable_vars and
+			 * forced_null_vars overlap: we need to know if the overlap
+			 * includes any RHS variables.
+			 */
+			overlap = list_intersection(local_nonnullable_vars,
+										forced_null_vars);
+			if (overlap != NIL &&
+				bms_overlap(pull_varnos(root, (Node *) overlap),
+							right_state->relids))
+				jointype = JOIN_ANTI;
+		}
+
+		/* Apply the jointype change, if any, to both jointree node and RTE */
+		if (rtindex && jointype != j->jointype)
+		{
+			RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable);
+
+			Assert(rte->rtekind == RTE_JOIN);
+			Assert(rte->jointype == j->jointype);
+			rte->jointype = jointype;
+		}
+		j->jointype = jointype;
+
+		/* Only recurse if there's more to do below here */
+		if (left_state->contains_outer || right_state->contains_outer)
+		{
+			Relids		local_nonnullable_rels;
+			List	   *local_forced_null_vars;
+			Relids		pass_nonnullable_rels;
+			List	   *pass_nonnullable_vars;
+			List	   *pass_forced_null_vars;
+
+			/*
+			 * If this join is (now) inner, we can add any constraints its
+			 * quals provide to those we got from above.  But if it is outer,
+			 * we can pass down the local constraints only into the nullable
+			 * side, because an outer join never eliminates any rows from its
+			 * non-nullable side.  Also, there is no point in passing upper
+			 * constraints into the nullable side, since if there were any
+			 * we'd have been able to reduce the join.  (In the case of upper
+			 * forced-null constraints, we *must not* pass them into the
+			 * nullable side --- they either applied here, or not.) The upshot
+			 * is that we pass either the local or the upper constraints,
+			 * never both, to the children of an outer join.
+			 *
+			 * Note that a SEMI join works like an inner join here: it's okay
+			 * to pass down both local and upper constraints.  (There can't be
+			 * any upper constraints affecting its inner side, but it's not
+			 * worth having a separate code path to avoid passing them.)
+			 *
+			 * At a FULL join we just punt and pass nothing down --- is it
+			 * possible to be smarter?
+			 */
+			if (jointype != JOIN_FULL)
+			{
+				local_nonnullable_rels = find_nonnullable_rels(j->quals);
+				if (!computed_local_nonnullable_vars)
+					local_nonnullable_vars = find_nonnullable_vars(j->quals);
+				local_forced_null_vars = find_forced_null_vars(j->quals);
+				if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
+				{
+					/* OK to merge upper and local constraints */
+					local_nonnullable_rels = bms_add_members(local_nonnullable_rels,
+															 nonnullable_rels);
+					local_nonnullable_vars = list_concat(local_nonnullable_vars,
+														 nonnullable_vars);
+					local_forced_null_vars = list_concat(local_forced_null_vars,
+														 forced_null_vars);
+				}
+			}
+			else
+			{
+				/* no use in calculating these */
+				local_nonnullable_rels = NULL;
+				local_forced_null_vars = NIL;
+			}
+
+			if (left_state->contains_outer)
+			{
+				if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
+				{
+					/* pass union of local and upper constraints */
+					pass_nonnullable_rels = local_nonnullable_rels;
+					pass_nonnullable_vars = local_nonnullable_vars;
+					pass_forced_null_vars = local_forced_null_vars;
+				}
+				else if (jointype != JOIN_FULL) /* ie, LEFT or ANTI */
+				{
+					/* can't pass local constraints to non-nullable side */
+					pass_nonnullable_rels = nonnullable_rels;
+					pass_nonnullable_vars = nonnullable_vars;
+					pass_forced_null_vars = forced_null_vars;
+				}
+				else
+				{
+					/* no constraints pass through JOIN_FULL */
+					pass_nonnullable_rels = NULL;
+					pass_nonnullable_vars = NIL;
+					pass_forced_null_vars = NIL;
+				}
+				reduce_outer_joins_pass2(j->larg, left_state, root,
+										 pass_nonnullable_rels,
+										 pass_nonnullable_vars,
+										 pass_forced_null_vars);
+			}
+
+			if (right_state->contains_outer)
+			{
+				if (jointype != JOIN_FULL)	/* ie, INNER/LEFT/SEMI/ANTI */
+				{
+					/* pass appropriate constraints, per comment above */
+					pass_nonnullable_rels = local_nonnullable_rels;
+					pass_nonnullable_vars = local_nonnullable_vars;
+					pass_forced_null_vars = local_forced_null_vars;
+				}
+				else
+				{
+					/* no constraints pass through JOIN_FULL */
+					pass_nonnullable_rels = NULL;
+					pass_nonnullable_vars = NIL;
+					pass_forced_null_vars = NIL;
+				}
+				reduce_outer_joins_pass2(j->rarg, right_state, root,
+										 pass_nonnullable_rels,
+										 pass_nonnullable_vars,
+										 pass_forced_null_vars);
+			}
+			bms_free(local_nonnullable_rels);
+		}
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+}
+
+
+/*
+ * remove_useless_result_rtes
+ *		Attempt to remove RTE_RESULT RTEs from the join tree.
+ *
+ * We can remove RTE_RESULT entries from the join tree using the knowledge
+ * that RTE_RESULT returns exactly one row and has no output columns.  Hence,
+ * if one is inner-joined to anything else, we can delete it.  Optimizations
+ * are also possible for some outer-join cases, as detailed below.
+ *
+ * Some of these optimizations depend on recognizing empty (constant-true)
+ * quals for FromExprs and JoinExprs.  That makes it useful to apply this
+ * optimization pass after expression preprocessing, since that will have
+ * eliminated constant-true quals, allowing more cases to be recognized as
+ * optimizable.  What's more, the usual reason for an RTE_RESULT to be present
+ * is that we pulled up a subquery or VALUES clause, thus very possibly
+ * replacing Vars with constants, making it more likely that a qual can be
+ * reduced to constant true.  Also, because some optimizations depend on
+ * the outer-join type, it's best to have done reduce_outer_joins() first.
+ *
+ * A PlaceHolderVar referencing an RTE_RESULT RTE poses an obstacle to this
+ * process: we must remove the RTE_RESULT's relid from the PHV's phrels, but
+ * we must not reduce the phrels set to empty.  If that would happen, and
+ * the RTE_RESULT is an immediate child of an outer join, we have to give up
+ * and not remove the RTE_RESULT: there is noplace else to evaluate the
+ * PlaceHolderVar.  (That is, in such cases the RTE_RESULT *does* have output
+ * columns.)  But if the RTE_RESULT is an immediate child of an inner join,
+ * we can usually change the PlaceHolderVar's phrels so as to evaluate it at
+ * the inner join instead.  This is OK because we really only care that PHVs
+ * are evaluated above or below the correct outer joins.  We can't, however,
+ * postpone the evaluation of a PHV to above where it is used; so there are
+ * some checks below on whether output PHVs are laterally referenced in the
+ * other join input rel(s).
+ *
+ * We used to try to do this work as part of pull_up_subqueries() where the
+ * potentially-optimizable cases get introduced; but it's way simpler, and
+ * more effective, to do it separately.
+ */
+void
+remove_useless_result_rtes(PlannerInfo *root)
+{
+	ListCell   *cell;
+
+	/* Top level of jointree must always be a FromExpr */
+	Assert(IsA(root->parse->jointree, FromExpr));
+	/* Recurse ... */
+	root->parse->jointree = (FromExpr *)
+		remove_useless_results_recurse(root, (Node *) root->parse->jointree);
+	/* We should still have a FromExpr */
+	Assert(IsA(root->parse->jointree, FromExpr));
+
+	/*
+	 * Remove any PlanRowMark referencing an RTE_RESULT RTE.  We obviously
+	 * must do that for any RTE_RESULT that we just removed.  But one for a
+	 * RTE that we did not remove can be dropped anyway: since the RTE has
+	 * only one possible output row, there is no need for EPQ to mark and
+	 * restore that row.
+	 *
+	 * It's necessary, not optional, to remove the PlanRowMark for a surviving
+	 * RTE_RESULT RTE; otherwise we'll generate a whole-row Var for the
+	 * RTE_RESULT, which the executor has no support for.
+	 */
+	foreach(cell, root->rowMarks)
+	{
+		PlanRowMark *rc = (PlanRowMark *) lfirst(cell);
+
+		if (rt_fetch(rc->rti, root->parse->rtable)->rtekind == RTE_RESULT)
+			root->rowMarks = foreach_delete_current(root->rowMarks, cell);
+	}
+}
+
+/*
+ * remove_useless_results_recurse
+ *		Recursive guts of remove_useless_result_rtes.
+ *
+ * This recursively processes the jointree and returns a modified jointree.
+ */
+static Node *
+remove_useless_results_recurse(PlannerInfo *root, Node *jtnode)
+{
+	Assert(jtnode != NULL);
+	if (IsA(jtnode, RangeTblRef))
+	{
+		/* Can't immediately do anything with a RangeTblRef */
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		Relids		result_relids = NULL;
+		ListCell   *cell;
+
+		/*
+		 * We can drop RTE_RESULT rels from the fromlist so long as at least
+		 * one child remains, since joining to a one-row table changes
+		 * nothing.  (But we can't drop a RTE_RESULT that computes PHV(s) that
+		 * are needed by some sibling.  The cleanup transformation below would
+		 * reassign the PHVs to be computed at the join, which is too late for
+		 * the sibling's use.)  The easiest way to mechanize this rule is to
+		 * modify the list in-place.
+		 */
+		foreach(cell, f->fromlist)
+		{
+			Node	   *child = (Node *) lfirst(cell);
+			int			varno;
+
+			/* Recursively transform child ... */
+			child = remove_useless_results_recurse(root, child);
+			/* ... and stick it back into the tree */
+			lfirst(cell) = child;
+
+			/*
+			 * If it's an RTE_RESULT with at least one sibling, and no sibling
+			 * references dependent PHVs, we can drop it.  We don't yet know
+			 * what the inner join's final relid set will be, so postpone
+			 * cleanup of PHVs etc till after this loop.
+			 */
+			if (list_length(f->fromlist) > 1 &&
+				(varno = get_result_relid(root, child)) != 0 &&
+				!find_dependent_phvs_in_jointree(root, (Node *) f, varno))
+			{
+				f->fromlist = foreach_delete_current(f->fromlist, cell);
+				result_relids = bms_add_member(result_relids, varno);
+			}
+		}
+
+		/*
+		 * Clean up if we dropped any RTE_RESULT RTEs.  This is a bit
+		 * inefficient if there's more than one, but it seems better to
+		 * optimize the support code for the single-relid case.
+		 */
+		if (result_relids)
+		{
+			int			varno = -1;
+
+			while ((varno = bms_next_member(result_relids, varno)) >= 0)
+				remove_result_refs(root, varno, (Node *) f);
+		}
+
+		/*
+		 * If we're not at the top of the jointree, it's valid to simplify a
+		 * degenerate FromExpr into its single child.  (At the top, we must
+		 * keep the FromExpr since Query.jointree is required to point to a
+		 * FromExpr.)
+		 */
+		if (f != root->parse->jointree &&
+			f->quals == NULL &&
+			list_length(f->fromlist) == 1)
+			return (Node *) linitial(f->fromlist);
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+		int			varno;
+
+		/* First, recurse */
+		j->larg = remove_useless_results_recurse(root, j->larg);
+		j->rarg = remove_useless_results_recurse(root, j->rarg);
+
+		/* Apply join-type-specific optimization rules */
+		switch (j->jointype)
+		{
+			case JOIN_INNER:
+
+				/*
+				 * An inner join is equivalent to a FromExpr, so if either
+				 * side was simplified to an RTE_RESULT rel, we can replace
+				 * the join with a FromExpr with just the other side; and if
+				 * the qual is empty (JOIN ON TRUE) then we can omit the
+				 * FromExpr as well.
+				 *
+				 * Just as in the FromExpr case, we can't simplify if the
+				 * other input rel references any PHVs that are marked as to
+				 * be evaluated at the RTE_RESULT rel, because we can't
+				 * postpone their evaluation in that case.  But we only have
+				 * to check this in cases where it's syntactically legal for
+				 * the other input to have a LATERAL reference to the
+				 * RTE_RESULT rel.  Only RHSes of inner and left joins are
+				 * allowed to have such refs.
+				 */
+				if ((varno = get_result_relid(root, j->larg)) != 0 &&
+					!find_dependent_phvs_in_jointree(root, j->rarg, varno))
+				{
+					remove_result_refs(root, varno, j->rarg);
+					if (j->quals)
+						jtnode = (Node *)
+							makeFromExpr(list_make1(j->rarg), j->quals);
+					else
+						jtnode = j->rarg;
+				}
+				else if ((varno = get_result_relid(root, j->rarg)) != 0)
+				{
+					remove_result_refs(root, varno, j->larg);
+					if (j->quals)
+						jtnode = (Node *)
+							makeFromExpr(list_make1(j->larg), j->quals);
+					else
+						jtnode = j->larg;
+				}
+				break;
+			case JOIN_LEFT:
+
+				/*
+				 * We can simplify this case if the RHS is an RTE_RESULT, with
+				 * two different possibilities:
+				 *
+				 * If the qual is empty (JOIN ON TRUE), then the join can be
+				 * strength-reduced to a plain inner join, since each LHS row
+				 * necessarily has exactly one join partner.  So we can always
+				 * discard the RHS, much as in the JOIN_INNER case above.
+				 * (Again, the LHS could not contain a lateral reference to
+				 * the RHS.)
+				 *
+				 * Otherwise, it's still true that each LHS row should be
+				 * returned exactly once, and since the RHS returns no columns
+				 * (unless there are PHVs that have to be evaluated there), we
+				 * don't much care if it's null-extended or not.  So in this
+				 * case also, we can just ignore the qual and discard the left
+				 * join.
+				 */
+				if ((varno = get_result_relid(root, j->rarg)) != 0 &&
+					(j->quals == NULL ||
+					 !find_dependent_phvs(root, varno)))
+				{
+					remove_result_refs(root, varno, j->larg);
+					jtnode = j->larg;
+				}
+				break;
+			case JOIN_RIGHT:
+				/* Mirror-image of the JOIN_LEFT case */
+				if ((varno = get_result_relid(root, j->larg)) != 0 &&
+					(j->quals == NULL ||
+					 !find_dependent_phvs(root, varno)))
+				{
+					remove_result_refs(root, varno, j->rarg);
+					jtnode = j->rarg;
+				}
+				break;
+			case JOIN_SEMI:
+
+				/*
+				 * We may simplify this case if the RHS is an RTE_RESULT; the
+				 * join qual becomes effectively just a filter qual for the
+				 * LHS, since we should either return the LHS row or not.  For
+				 * simplicity we inject the filter qual into a new FromExpr.
+				 *
+				 * Unlike the LEFT/RIGHT cases, we just Assert that there are
+				 * no PHVs that need to be evaluated at the semijoin's RHS,
+				 * since the rest of the query couldn't reference any outputs
+				 * of the semijoin's RHS.
+				 */
+				if ((varno = get_result_relid(root, j->rarg)) != 0)
+				{
+					Assert(!find_dependent_phvs(root, varno));
+					remove_result_refs(root, varno, j->larg);
+					if (j->quals)
+						jtnode = (Node *)
+							makeFromExpr(list_make1(j->larg), j->quals);
+					else
+						jtnode = j->larg;
+				}
+				break;
+			case JOIN_FULL:
+			case JOIN_ANTI:
+				/* We have no special smarts for these cases */
+				break;
+			default:
+				elog(ERROR, "unrecognized join type: %d",
+					 (int) j->jointype);
+				break;
+		}
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return jtnode;
+}
+
+/*
+ * get_result_relid
+ *		If jtnode is a RangeTblRef for an RTE_RESULT RTE, return its relid;
+ *		otherwise return 0.
+ */
+static int
+get_result_relid(PlannerInfo *root, Node *jtnode)
+{
+	int			varno;
+
+	if (!IsA(jtnode, RangeTblRef))
+		return 0;
+	varno = ((RangeTblRef *) jtnode)->rtindex;
+	if (rt_fetch(varno, root->parse->rtable)->rtekind != RTE_RESULT)
+		return 0;
+	return varno;
+}
+
+/*
+ * remove_result_refs
+ *		Helper routine for dropping an unneeded RTE_RESULT RTE.
+ *
+ * This doesn't physically remove the RTE from the jointree, because that's
+ * more easily handled in remove_useless_results_recurse.  What it does do
+ * is the necessary cleanup in the rest of the tree: we must adjust any PHVs
+ * that may reference the RTE.  Be sure to call this at a point where the
+ * jointree is valid (no disconnected nodes).
+ *
+ * Note that we don't need to process the append_rel_list, since RTEs
+ * referenced directly in the jointree won't be appendrel members.
+ *
+ * varno is the RTE_RESULT's relid.
+ * newjtloc is the jointree location at which any PHVs referencing the
+ * RTE_RESULT should be evaluated instead.
+ */
+static void
+remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc)
+{
+	/* Fix up PlaceHolderVars as needed */
+	/* If there are no PHVs anywhere, we can skip this bit */
+	if (root->glob->lastPHId != 0)
+	{
+		Relids		subrelids;
+
+		subrelids = get_relids_in_jointree(newjtloc, false);
+		Assert(!bms_is_empty(subrelids));
+		substitute_phv_relids((Node *) root->parse, varno, subrelids);
+		fix_append_rel_relids(root->append_rel_list, varno, subrelids);
+	}
+
+	/*
+	 * We also need to remove any PlanRowMark referencing the RTE, but we
+	 * postpone that work until we return to remove_useless_result_rtes.
+	 */
+}
+
+
+/*
+ * find_dependent_phvs - are there any PlaceHolderVars whose relids are
+ * exactly the given varno?
+ *
+ * find_dependent_phvs should be used when we want to see if there are
+ * any such PHVs anywhere in the Query.  Another use-case is to see if
+ * a subtree of the join tree contains such PHVs; but for that, we have
+ * to look not only at the join tree nodes themselves but at the
+ * referenced RTEs.  For that, use find_dependent_phvs_in_jointree.
+ */
+
+typedef struct
+{
+	Relids		relids;
+	int			sublevels_up;
+} find_dependent_phvs_context;
+
+static bool
+find_dependent_phvs_walker(Node *node,
+						   find_dependent_phvs_context *context)
+{
+	if (node == NULL)
+		return false;
+	if (IsA(node, PlaceHolderVar))
+	{
+		PlaceHolderVar *phv = (PlaceHolderVar *) node;
+
+		if (phv->phlevelsup == context->sublevels_up &&
+			bms_equal(context->relids, phv->phrels))
+			return true;
+		/* fall through to examine children */
+	}
+	if (IsA(node, Query))
+	{
+		/* Recurse into subselects */
+		bool		result;
+
+		context->sublevels_up++;
+		result = query_tree_walker((Query *) node,
+								   find_dependent_phvs_walker,
+								   (void *) context, 0);
+		context->sublevels_up--;
+		return result;
+	}
+	/* Shouldn't need to handle planner auxiliary nodes here */
+	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, AppendRelInfo));
+	Assert(!IsA(node, PlaceHolderInfo));
+	Assert(!IsA(node, MinMaxAggInfo));
+
+	return expression_tree_walker(node, find_dependent_phvs_walker,
+								  (void *) context);
+}
+
+static bool
+find_dependent_phvs(PlannerInfo *root, int varno)
+{
+	find_dependent_phvs_context context;
+
+	/* If there are no PHVs anywhere, we needn't work hard */
+	if (root->glob->lastPHId == 0)
+		return false;
+
+	context.relids = bms_make_singleton(varno);
+	context.sublevels_up = 0;
+
+	return query_tree_walker(root->parse,
+							 find_dependent_phvs_walker,
+							 (void *) &context,
+							 0);
+}
+
+static bool
+find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno)
+{
+	find_dependent_phvs_context context;
+	Relids		subrelids;
+	int			relid;
+
+	/* If there are no PHVs anywhere, we needn't work hard */
+	if (root->glob->lastPHId == 0)
+		return false;
+
+	context.relids = bms_make_singleton(varno);
+	context.sublevels_up = 0;
+
+	/*
+	 * See if the jointree fragment itself contains references (in join quals)
+	 */
+	if (find_dependent_phvs_walker(node, &context))
+		return true;
+
+	/*
+	 * Otherwise, identify the set of referenced RTEs (we can ignore joins,
+	 * since they should be flattened already, so their join alias lists no
+	 * longer matter), and tediously check each RTE.  We can ignore RTEs that
+	 * are not marked LATERAL, though, since they couldn't possibly contain
+	 * any cross-references to other RTEs.
+	 */
+	subrelids = get_relids_in_jointree(node, false);
+	relid = -1;
+	while ((relid = bms_next_member(subrelids, relid)) >= 0)
+	{
+		RangeTblEntry *rte = rt_fetch(relid, root->parse->rtable);
+
+		if (rte->lateral &&
+			range_table_entry_walker(rte,
+									 find_dependent_phvs_walker,
+									 (void *) &context,
+									 0))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * substitute_phv_relids - adjust PlaceHolderVar relid sets after pulling up
+ * a subquery or removing an RTE_RESULT jointree item
+ *
+ * Find any PlaceHolderVar nodes in the given tree that reference the
+ * pulled-up relid, and change them to reference the replacement relid(s).
+ *
+ * NOTE: although this has the form of a walker, we cheat and modify the
+ * nodes in-place.  This should be OK since the tree was copied by
+ * pullup_replace_vars earlier.  Avoid scribbling on the original values of
+ * the bitmapsets, though, because expression_tree_mutator doesn't copy those.
+ */
+
+typedef struct
+{
+	int			varno;
+	int			sublevels_up;
+	Relids		subrelids;
+} substitute_phv_relids_context;
+
+static bool
+substitute_phv_relids_walker(Node *node,
+							 substitute_phv_relids_context *context)
+{
+	if (node == NULL)
+		return false;
+	if (IsA(node, PlaceHolderVar))
+	{
+		PlaceHolderVar *phv = (PlaceHolderVar *) node;
+
+		if (phv->phlevelsup == context->sublevels_up &&
+			bms_is_member(context->varno, phv->phrels))
+		{
+			phv->phrels = bms_union(phv->phrels,
+									context->subrelids);
+			phv->phrels = bms_del_member(phv->phrels,
+										 context->varno);
+			/* Assert we haven't broken the PHV */
+			Assert(!bms_is_empty(phv->phrels));
+		}
+		/* fall through to examine children */
+	}
+	if (IsA(node, Query))
+	{
+		/* Recurse into subselects */
+		bool		result;
+
+		context->sublevels_up++;
+		result = query_tree_walker((Query *) node,
+								   substitute_phv_relids_walker,
+								   (void *) context, 0);
+		context->sublevels_up--;
+		return result;
+	}
+	/* Shouldn't need to handle planner auxiliary nodes here */
+	Assert(!IsA(node, SpecialJoinInfo));
+	Assert(!IsA(node, AppendRelInfo));
+	Assert(!IsA(node, PlaceHolderInfo));
+	Assert(!IsA(node, MinMaxAggInfo));
+
+	return expression_tree_walker(node, substitute_phv_relids_walker,
+								  (void *) context);
+}
+
+static void
+substitute_phv_relids(Node *node, int varno, Relids subrelids)
+{
+	substitute_phv_relids_context context;
+
+	context.varno = varno;
+	context.sublevels_up = 0;
+	context.subrelids = subrelids;
+
+	/*
+	 * Must be prepared to start with a Query or a bare expression tree.
+	 */
+	query_or_expression_tree_walker(node,
+									substitute_phv_relids_walker,
+									(void *) &context,
+									0);
+}
+
+/*
+ * fix_append_rel_relids: update RT-index fields of AppendRelInfo nodes
+ *
+ * When we pull up a subquery, any AppendRelInfo references to the subquery's
+ * RT index have to be replaced by the substituted relid (and there had better
+ * be only one).  We also need to apply substitute_phv_relids to their
+ * translated_vars lists, since those might contain PlaceHolderVars.
+ *
+ * We assume we may modify the AppendRelInfo nodes in-place.
+ */
+static void
+fix_append_rel_relids(List *append_rel_list, int varno, Relids subrelids)
+{
+	ListCell   *l;
+	int			subvarno = -1;
+
+	/*
+	 * We only want to extract the member relid once, but we mustn't fail
+	 * immediately if there are multiple members; it could be that none of the
+	 * AppendRelInfo nodes refer to it.  So compute it on first use. Note that
+	 * bms_singleton_member will complain if set is not singleton.
+	 */
+	foreach(l, append_rel_list)
+	{
+		AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
+
+		/* The parent_relid shouldn't ever be a pullup target */
+		Assert(appinfo->parent_relid != varno);
+
+		if (appinfo->child_relid == varno)
+		{
+			if (subvarno < 0)
+				subvarno = bms_singleton_member(subrelids);
+			appinfo->child_relid = subvarno;
+		}
+
+		/* Also fix up any PHVs in its translated vars */
+		substitute_phv_relids((Node *) appinfo->translated_vars,
+							  varno, subrelids);
+	}
+}
+
+/*
+ * get_relids_in_jointree: get set of RT indexes present in a jointree
+ *
+ * If include_joins is true, join RT indexes are included; if false,
+ * only base rels are included.
+ */
+Relids
+get_relids_in_jointree(Node *jtnode, bool include_joins)
+{
+	Relids		result = NULL;
+
+	if (jtnode == NULL)
+		return result;
+	if (IsA(jtnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+
+		result = bms_make_singleton(varno);
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		foreach(l, f->fromlist)
+		{
+			result = bms_join(result,
+							  get_relids_in_jointree(lfirst(l),
+													 include_joins));
+		}
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+
+		result = get_relids_in_jointree(j->larg, include_joins);
+		result = bms_join(result,
+						  get_relids_in_jointree(j->rarg, include_joins));
+		if (include_joins && j->rtindex)
+			result = bms_add_member(result, j->rtindex);
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return result;
+}
+
+/*
+ * get_relids_for_join: get set of base RT indexes making up a join
+ */
+Relids
+get_relids_for_join(Query *query, int joinrelid)
+{
+	Node	   *jtnode;
+
+	jtnode = find_jointree_node_for_rel((Node *) query->jointree,
+										joinrelid);
+	if (!jtnode)
+		elog(ERROR, "could not find join node %d", joinrelid);
+	return get_relids_in_jointree(jtnode, false);
+}
+
+/*
+ * find_jointree_node_for_rel: locate jointree node for a base or join RT index
+ *
+ * Returns NULL if not found
+ */
+static Node *
+find_jointree_node_for_rel(Node *jtnode, int relid)
+{
+	if (jtnode == NULL)
+		return NULL;
+	if (IsA(jtnode, RangeTblRef))
+	{
+		int			varno = ((RangeTblRef *) jtnode)->rtindex;
+
+		if (relid == varno)
+			return jtnode;
+	}
+	else if (IsA(jtnode, FromExpr))
+	{
+		FromExpr   *f = (FromExpr *) jtnode;
+		ListCell   *l;
+
+		foreach(l, f->fromlist)
+		{
+			jtnode = find_jointree_node_for_rel(lfirst(l), relid);
+			if (jtnode)
+				return jtnode;
+		}
+	}
+	else if (IsA(jtnode, JoinExpr))
+	{
+		JoinExpr   *j = (JoinExpr *) jtnode;
+
+		if (relid == j->rtindex)
+			return jtnode;
+		jtnode = find_jointree_node_for_rel(j->larg, relid);
+		if (jtnode)
+			return jtnode;
+		jtnode = find_jointree_node_for_rel(j->rarg, relid);
+		if (jtnode)
+			return jtnode;
+	}
+	else
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(jtnode));
+	return NULL;
+}
diff --git a/src/backend/optimizer/prep/prepqual.c b/src/backend/optimizer/prep/prepqual.c
new file mode 100644
index 0000000..42c3e4d
--- /dev/null
+++ b/src/backend/optimizer/prep/prepqual.c
@@ -0,0 +1,676 @@
+/*-------------------------------------------------------------------------
+ *
+ * prepqual.c
+ *	  Routines for preprocessing qualification expressions
+ *
+ *
+ * While the parser will produce flattened (N-argument) AND/OR trees from
+ * simple sequences of AND'ed or OR'ed clauses, there might be an AND clause
+ * directly underneath another AND, or OR underneath OR, if the input was
+ * oddly parenthesized.  Also, rule expansion and subquery flattening could
+ * produce such parsetrees.  The planner wants to flatten all such cases
+ * to ensure consistent optimization behavior.
+ *
+ * Formerly, this module was responsible for doing the initial flattening,
+ * but now we leave it to eval_const_expressions to do that since it has to
+ * make a complete pass over the expression tree anyway.  Instead, we just
+ * have to ensure that our manipulations preserve AND/OR flatness.
+ * pull_ands() and pull_ors() are used to maintain flatness of the AND/OR
+ * tree after local transformations that might introduce nested AND/ORs.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/prep/prepqual.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/prep.h"
+#include "utils/lsyscache.h"
+
+
+static List *pull_ands(List *andlist);
+static List *pull_ors(List *orlist);
+static Expr *find_duplicate_ors(Expr *qual, bool is_check);
+static Expr *process_duplicate_ors(List *orlist);
+
+
+/*
+ * negate_clause
+ *	  Negate a Boolean expression.
+ *
+ * Input is a clause to be negated (e.g., the argument of a NOT clause).
+ * Returns a new clause equivalent to the negation of the given clause.
+ *
+ * Although this can be invoked on its own, it's mainly intended as a helper
+ * for eval_const_expressions(), and that context drives several design
+ * decisions.  In particular, if the input is already AND/OR flat, we must
+ * preserve that property.  We also don't bother to recurse in situations
+ * where we can assume that lower-level executions of eval_const_expressions
+ * would already have simplified sub-clauses of the input.
+ *
+ * The difference between this and a simple make_notclause() is that this
+ * tries to get rid of the NOT node by logical simplification.  It's clearly
+ * always a win if the NOT node can be eliminated altogether.  However, our
+ * use of DeMorgan's laws could result in having more NOT nodes rather than
+ * fewer.  We do that unconditionally anyway, because in WHERE clauses it's
+ * important to expose as much top-level AND/OR structure as possible.
+ * Also, eliminating an intermediate NOT may allow us to flatten two levels
+ * of AND or OR together that we couldn't have otherwise.  Finally, one of
+ * the motivations for doing this is to ensure that logically equivalent
+ * expressions will be seen as physically equal(), so we should always apply
+ * the same transformations.
+ */
+Node *
+negate_clause(Node *node)
+{
+	if (node == NULL)			/* should not happen */
+		elog(ERROR, "can't negate an empty subexpression");
+	switch (nodeTag(node))
+	{
+		case T_Const:
+			{
+				Const	   *c = (Const *) node;
+
+				/* NOT NULL is still NULL */
+				if (c->constisnull)
+					return makeBoolConst(false, true);
+				/* otherwise pretty easy */
+				return makeBoolConst(!DatumGetBool(c->constvalue), false);
+			}
+			break;
+		case T_OpExpr:
+			{
+				/*
+				 * Negate operator if possible: (NOT (< A B)) => (>= A B)
+				 */
+				OpExpr	   *opexpr = (OpExpr *) node;
+				Oid			negator = get_negator(opexpr->opno);
+
+				if (negator)
+				{
+					OpExpr	   *newopexpr = makeNode(OpExpr);
+
+					newopexpr->opno = negator;
+					newopexpr->opfuncid = InvalidOid;
+					newopexpr->opresulttype = opexpr->opresulttype;
+					newopexpr->opretset = opexpr->opretset;
+					newopexpr->opcollid = opexpr->opcollid;
+					newopexpr->inputcollid = opexpr->inputcollid;
+					newopexpr->args = opexpr->args;
+					newopexpr->location = opexpr->location;
+					return (Node *) newopexpr;
+				}
+			}
+			break;
+		case T_ScalarArrayOpExpr:
+			{
+				/*
+				 * Negate a ScalarArrayOpExpr if its operator has a negator;
+				 * for example x = ANY (list) becomes x <> ALL (list)
+				 */
+				ScalarArrayOpExpr *saopexpr = (ScalarArrayOpExpr *) node;
+				Oid			negator = get_negator(saopexpr->opno);
+
+				if (negator)
+				{
+					ScalarArrayOpExpr *newopexpr = makeNode(ScalarArrayOpExpr);
+
+					newopexpr->opno = negator;
+					newopexpr->opfuncid = InvalidOid;
+					newopexpr->hashfuncid = InvalidOid;
+					newopexpr->useOr = !saopexpr->useOr;
+					newopexpr->inputcollid = saopexpr->inputcollid;
+					newopexpr->args = saopexpr->args;
+					newopexpr->location = saopexpr->location;
+					return (Node *) newopexpr;
+				}
+			}
+			break;
+		case T_BoolExpr:
+			{
+				BoolExpr   *expr = (BoolExpr *) node;
+
+				switch (expr->boolop)
+				{
+						/*--------------------
+						 * Apply DeMorgan's Laws:
+						 *		(NOT (AND A B)) => (OR (NOT A) (NOT B))
+						 *		(NOT (OR A B))	=> (AND (NOT A) (NOT B))
+						 * i.e., swap AND for OR and negate each subclause.
+						 *
+						 * If the input is already AND/OR flat and has no NOT
+						 * directly above AND or OR, this transformation preserves
+						 * those properties.  For example, if no direct child of
+						 * the given AND clause is an AND or a NOT-above-OR, then
+						 * the recursive calls of negate_clause() can't return any
+						 * OR clauses.  So we needn't call pull_ors() before
+						 * building a new OR clause.  Similarly for the OR case.
+						 *--------------------
+						 */
+					case AND_EXPR:
+						{
+							List	   *nargs = NIL;
+							ListCell   *lc;
+
+							foreach(lc, expr->args)
+							{
+								nargs = lappend(nargs,
+												negate_clause(lfirst(lc)));
+							}
+							return (Node *) make_orclause(nargs);
+						}
+						break;
+					case OR_EXPR:
+						{
+							List	   *nargs = NIL;
+							ListCell   *lc;
+
+							foreach(lc, expr->args)
+							{
+								nargs = lappend(nargs,
+												negate_clause(lfirst(lc)));
+							}
+							return (Node *) make_andclause(nargs);
+						}
+						break;
+					case NOT_EXPR:
+
+						/*
+						 * NOT underneath NOT: they cancel.  We assume the
+						 * input is already simplified, so no need to recurse.
+						 */
+						return (Node *) linitial(expr->args);
+					default:
+						elog(ERROR, "unrecognized boolop: %d",
+							 (int) expr->boolop);
+						break;
+				}
+			}
+			break;
+		case T_NullTest:
+			{
+				NullTest   *expr = (NullTest *) node;
+
+				/*
+				 * In the rowtype case, the two flavors of NullTest are *not*
+				 * logical inverses, so we can't simplify.  But it does work
+				 * for scalar datatypes.
+				 */
+				if (!expr->argisrow)
+				{
+					NullTest   *newexpr = makeNode(NullTest);
+
+					newexpr->arg = expr->arg;
+					newexpr->nulltesttype = (expr->nulltesttype == IS_NULL ?
+											 IS_NOT_NULL : IS_NULL);
+					newexpr->argisrow = expr->argisrow;
+					newexpr->location = expr->location;
+					return (Node *) newexpr;
+				}
+			}
+			break;
+		case T_BooleanTest:
+			{
+				BooleanTest *expr = (BooleanTest *) node;
+				BooleanTest *newexpr = makeNode(BooleanTest);
+
+				newexpr->arg = expr->arg;
+				switch (expr->booltesttype)
+				{
+					case IS_TRUE:
+						newexpr->booltesttype = IS_NOT_TRUE;
+						break;
+					case IS_NOT_TRUE:
+						newexpr->booltesttype = IS_TRUE;
+						break;
+					case IS_FALSE:
+						newexpr->booltesttype = IS_NOT_FALSE;
+						break;
+					case IS_NOT_FALSE:
+						newexpr->booltesttype = IS_FALSE;
+						break;
+					case IS_UNKNOWN:
+						newexpr->booltesttype = IS_NOT_UNKNOWN;
+						break;
+					case IS_NOT_UNKNOWN:
+						newexpr->booltesttype = IS_UNKNOWN;
+						break;
+					default:
+						elog(ERROR, "unrecognized booltesttype: %d",
+							 (int) expr->booltesttype);
+						break;
+				}
+				newexpr->location = expr->location;
+				return (Node *) newexpr;
+			}
+			break;
+		default:
+			/* else fall through */
+			break;
+	}
+
+	/*
+	 * Otherwise we don't know how to simplify this, so just tack on an
+	 * explicit NOT node.
+	 */
+	return (Node *) make_notclause((Expr *) node);
+}
+
+
+/*
+ * canonicalize_qual
+ *	  Convert a qualification expression to the most useful form.
+ *
+ * This is primarily intended to be used on top-level WHERE (or JOIN/ON)
+ * clauses.  It can also be used on top-level CHECK constraints, for which
+ * pass is_check = true.  DO NOT call it on any expression that is not known
+ * to be one or the other, as it might apply inappropriate simplifications.
+ *
+ * The name of this routine is a holdover from a time when it would try to
+ * force the expression into canonical AND-of-ORs or OR-of-ANDs form.
+ * Eventually, we recognized that that had more theoretical purity than
+ * actual usefulness, and so now the transformation doesn't involve any
+ * notion of reaching a canonical form.
+ *
+ * NOTE: we assume the input has already been through eval_const_expressions
+ * and therefore possesses AND/OR flatness.  Formerly this function included
+ * its own flattening logic, but that requires a useless extra pass over the
+ * tree.
+ *
+ * Returns the modified qualification.
+ */
+Expr *
+canonicalize_qual(Expr *qual, bool is_check)
+{
+	Expr	   *newqual;
+
+	/* Quick exit for empty qual */
+	if (qual == NULL)
+		return NULL;
+
+	/* This should not be invoked on quals in implicit-AND format */
+	Assert(!IsA(qual, List));
+
+	/*
+	 * Pull up redundant subclauses in OR-of-AND trees.  We do this only
+	 * within the top-level AND/OR structure; there's no point in looking
+	 * deeper.  Also remove any NULL constants in the top-level structure.
+	 */
+	newqual = find_duplicate_ors(qual, is_check);
+
+	return newqual;
+}
+
+
+/*
+ * pull_ands
+ *	  Recursively flatten nested AND clauses into a single and-clause list.
+ *
+ * Input is the arglist of an AND clause.
+ * Returns the rebuilt arglist (note original list structure is not touched).
+ */
+static List *
+pull_ands(List *andlist)
+{
+	List	   *out_list = NIL;
+	ListCell   *arg;
+
+	foreach(arg, andlist)
+	{
+		Node	   *subexpr = (Node *) lfirst(arg);
+
+		if (is_andclause(subexpr))
+			out_list = list_concat(out_list,
+								   pull_ands(((BoolExpr *) subexpr)->args));
+		else
+			out_list = lappend(out_list, subexpr);
+	}
+	return out_list;
+}
+
+/*
+ * pull_ors
+ *	  Recursively flatten nested OR clauses into a single or-clause list.
+ *
+ * Input is the arglist of an OR clause.
+ * Returns the rebuilt arglist (note original list structure is not touched).
+ */
+static List *
+pull_ors(List *orlist)
+{
+	List	   *out_list = NIL;
+	ListCell   *arg;
+
+	foreach(arg, orlist)
+	{
+		Node	   *subexpr = (Node *) lfirst(arg);
+
+		if (is_orclause(subexpr))
+			out_list = list_concat(out_list,
+								   pull_ors(((BoolExpr *) subexpr)->args));
+		else
+			out_list = lappend(out_list, subexpr);
+	}
+	return out_list;
+}
+
+
+/*--------------------
+ * The following code attempts to apply the inverse OR distributive law:
+ *		((A AND B) OR (A AND C))  =>  (A AND (B OR C))
+ * That is, locate OR clauses in which every subclause contains an
+ * identical term, and pull out the duplicated terms.
+ *
+ * This may seem like a fairly useless activity, but it turns out to be
+ * applicable to many machine-generated queries, and there are also queries
+ * in some of the TPC benchmarks that need it.  This was in fact almost the
+ * sole useful side-effect of the old prepqual code that tried to force
+ * the query into canonical AND-of-ORs form: the canonical equivalent of
+ *		((A AND B) OR (A AND C))
+ * is
+ *		((A OR A) AND (A OR C) AND (B OR A) AND (B OR C))
+ * which the code was able to simplify to
+ *		(A AND (A OR C) AND (B OR A) AND (B OR C))
+ * thus successfully extracting the common condition A --- but at the cost
+ * of cluttering the qual with many redundant clauses.
+ *--------------------
+ */
+
+/*
+ * find_duplicate_ors
+ *	  Given a qualification tree with the NOTs pushed down, search for
+ *	  OR clauses to which the inverse OR distributive law might apply.
+ *	  Only the top-level AND/OR structure is searched.
+ *
+ * While at it, we remove any NULL constants within the top-level AND/OR
+ * structure, eg in a WHERE clause, "x OR NULL::boolean" is reduced to "x".
+ * In general that would change the result, so eval_const_expressions can't
+ * do it; but at top level of WHERE, we don't need to distinguish between
+ * FALSE and NULL results, so it's valid to treat NULL::boolean the same
+ * as FALSE and then simplify AND/OR accordingly.  Conversely, in a top-level
+ * CHECK constraint, we may treat a NULL the same as TRUE.
+ *
+ * Returns the modified qualification.  AND/OR flatness is preserved.
+ */
+static Expr *
+find_duplicate_ors(Expr *qual, bool is_check)
+{
+	if (is_orclause(qual))
+	{
+		List	   *orlist = NIL;
+		ListCell   *temp;
+
+		/* Recurse */
+		foreach(temp, ((BoolExpr *) qual)->args)
+		{
+			Expr	   *arg = (Expr *) lfirst(temp);
+
+			arg = find_duplicate_ors(arg, is_check);
+
+			/* Get rid of any constant inputs */
+			if (arg && IsA(arg, Const))
+			{
+				Const	   *carg = (Const *) arg;
+
+				if (is_check)
+				{
+					/* Within OR in CHECK, drop constant FALSE */
+					if (!carg->constisnull && !DatumGetBool(carg->constvalue))
+						continue;
+					/* Constant TRUE or NULL, so OR reduces to TRUE */
+					return (Expr *) makeBoolConst(true, false);
+				}
+				else
+				{
+					/* Within OR in WHERE, drop constant FALSE or NULL */
+					if (carg->constisnull || !DatumGetBool(carg->constvalue))
+						continue;
+					/* Constant TRUE, so OR reduces to TRUE */
+					return arg;
+				}
+			}
+
+			orlist = lappend(orlist, arg);
+		}
+
+		/* Flatten any ORs pulled up to just below here */
+		orlist = pull_ors(orlist);
+
+		/* Now we can look for duplicate ORs */
+		return process_duplicate_ors(orlist);
+	}
+	else if (is_andclause(qual))
+	{
+		List	   *andlist = NIL;
+		ListCell   *temp;
+
+		/* Recurse */
+		foreach(temp, ((BoolExpr *) qual)->args)
+		{
+			Expr	   *arg = (Expr *) lfirst(temp);
+
+			arg = find_duplicate_ors(arg, is_check);
+
+			/* Get rid of any constant inputs */
+			if (arg && IsA(arg, Const))
+			{
+				Const	   *carg = (Const *) arg;
+
+				if (is_check)
+				{
+					/* Within AND in CHECK, drop constant TRUE or NULL */
+					if (carg->constisnull || DatumGetBool(carg->constvalue))
+						continue;
+					/* Constant FALSE, so AND reduces to FALSE */
+					return arg;
+				}
+				else
+				{
+					/* Within AND in WHERE, drop constant TRUE */
+					if (!carg->constisnull && DatumGetBool(carg->constvalue))
+						continue;
+					/* Constant FALSE or NULL, so AND reduces to FALSE */
+					return (Expr *) makeBoolConst(false, false);
+				}
+			}
+
+			andlist = lappend(andlist, arg);
+		}
+
+		/* Flatten any ANDs introduced just below here */
+		andlist = pull_ands(andlist);
+
+		/* AND of no inputs reduces to TRUE */
+		if (andlist == NIL)
+			return (Expr *) makeBoolConst(true, false);
+
+		/* Single-expression AND just reduces to that expression */
+		if (list_length(andlist) == 1)
+			return (Expr *) linitial(andlist);
+
+		/* Else we still need an AND node */
+		return make_andclause(andlist);
+	}
+	else
+		return qual;
+}
+
+/*
+ * process_duplicate_ors
+ *	  Given a list of exprs which are ORed together, try to apply
+ *	  the inverse OR distributive law.
+ *
+ * Returns the resulting expression (could be an AND clause, an OR
+ * clause, or maybe even a single subexpression).
+ */
+static Expr *
+process_duplicate_ors(List *orlist)
+{
+	List	   *reference = NIL;
+	int			num_subclauses = 0;
+	List	   *winners;
+	List	   *neworlist;
+	ListCell   *temp;
+
+	/* OR of no inputs reduces to FALSE */
+	if (orlist == NIL)
+		return (Expr *) makeBoolConst(false, false);
+
+	/* Single-expression OR just reduces to that expression */
+	if (list_length(orlist) == 1)
+		return (Expr *) linitial(orlist);
+
+	/*
+	 * Choose the shortest AND clause as the reference list --- obviously, any
+	 * subclause not in this clause isn't in all the clauses. If we find a
+	 * clause that's not an AND, we can treat it as a one-element AND clause,
+	 * which necessarily wins as shortest.
+	 */
+	foreach(temp, orlist)
+	{
+		Expr	   *clause = (Expr *) lfirst(temp);
+
+		if (is_andclause(clause))
+		{
+			List	   *subclauses = ((BoolExpr *) clause)->args;
+			int			nclauses = list_length(subclauses);
+
+			if (reference == NIL || nclauses < num_subclauses)
+			{
+				reference = subclauses;
+				num_subclauses = nclauses;
+			}
+		}
+		else
+		{
+			reference = list_make1(clause);
+			break;
+		}
+	}
+
+	/*
+	 * Just in case, eliminate any duplicates in the reference list.
+	 */
+	reference = list_union(NIL, reference);
+
+	/*
+	 * Check each element of the reference list to see if it's in all the OR
+	 * clauses.  Build a new list of winning clauses.
+	 */
+	winners = NIL;
+	foreach(temp, reference)
+	{
+		Expr	   *refclause = (Expr *) lfirst(temp);
+		bool		win = true;
+		ListCell   *temp2;
+
+		foreach(temp2, orlist)
+		{
+			Expr	   *clause = (Expr *) lfirst(temp2);
+
+			if (is_andclause(clause))
+			{
+				if (!list_member(((BoolExpr *) clause)->args, refclause))
+				{
+					win = false;
+					break;
+				}
+			}
+			else
+			{
+				if (!equal(refclause, clause))
+				{
+					win = false;
+					break;
+				}
+			}
+		}
+
+		if (win)
+			winners = lappend(winners, refclause);
+	}
+
+	/*
+	 * If no winners, we can't transform the OR
+	 */
+	if (winners == NIL)
+		return make_orclause(orlist);
+
+	/*
+	 * Generate new OR list consisting of the remaining sub-clauses.
+	 *
+	 * If any clause degenerates to empty, then we have a situation like (A
+	 * AND B) OR (A), which can be reduced to just A --- that is, the
+	 * additional conditions in other arms of the OR are irrelevant.
+	 *
+	 * Note that because we use list_difference, any multiple occurrences of a
+	 * winning clause in an AND sub-clause will be removed automatically.
+	 */
+	neworlist = NIL;
+	foreach(temp, orlist)
+	{
+		Expr	   *clause = (Expr *) lfirst(temp);
+
+		if (is_andclause(clause))
+		{
+			List	   *subclauses = ((BoolExpr *) clause)->args;
+
+			subclauses = list_difference(subclauses, winners);
+			if (subclauses != NIL)
+			{
+				if (list_length(subclauses) == 1)
+					neworlist = lappend(neworlist, linitial(subclauses));
+				else
+					neworlist = lappend(neworlist, make_andclause(subclauses));
+			}
+			else
+			{
+				neworlist = NIL;	/* degenerate case, see above */
+				break;
+			}
+		}
+		else
+		{
+			if (!list_member(winners, clause))
+				neworlist = lappend(neworlist, clause);
+			else
+			{
+				neworlist = NIL;	/* degenerate case, see above */
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Append reduced OR to the winners list, if it's not degenerate, handling
+	 * the special case of one element correctly (can that really happen?).
+	 * Also be careful to maintain AND/OR flatness in case we pulled up a
+	 * sub-sub-OR-clause.
+	 */
+	if (neworlist != NIL)
+	{
+		if (list_length(neworlist) == 1)
+			winners = lappend(winners, linitial(neworlist));
+		else
+			winners = lappend(winners, make_orclause(pull_ors(neworlist)));
+	}
+
+	/*
+	 * And return the constructed AND clause, again being wary of a single
+	 * element and AND/OR flatness.
+	 */
+	if (list_length(winners) == 1)
+		return (Expr *) linitial(winners);
+	else
+		return make_andclause(pull_ands(winners));
+}
diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c
new file mode 100644
index 0000000..e943458
--- /dev/null
+++ b/src/backend/optimizer/prep/preptlist.c
@@ -0,0 +1,437 @@
+/*-------------------------------------------------------------------------
+ *
+ * preptlist.c
+ *	  Routines to preprocess the parse tree target list
+ *
+ * For an INSERT, the targetlist must contain an entry for each attribute of
+ * the target relation in the correct order.
+ *
+ * For an UPDATE, the targetlist just contains the expressions for the new
+ * column values.
+ *
+ * For UPDATE and DELETE queries, the targetlist must also contain "junk"
+ * tlist entries needed to allow the executor to identify the rows to be
+ * updated or deleted; for example, the ctid of a heap row.  (The planner
+ * adds these; they're not in what we receive from the planner/rewriter.)
+ *
+ * For all query types, there can be additional junk tlist entries, such as
+ * sort keys, Vars needed for a RETURNING list, and row ID information needed
+ * for SELECT FOR UPDATE locking and/or EvalPlanQual checking.
+ *
+ * The query rewrite phase also does preprocessing of the targetlist (see
+ * rewriteTargetListIU).  The division of labor between here and there is
+ * partially historical, but it's not entirely arbitrary.  The stuff done
+ * here is closely connected to physical access to tables, whereas the
+ * rewriter's work is more concerned with SQL semantics.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/prep/preptlist.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/table.h"
+#include "nodes/makefuncs.h"
+#include "optimizer/appendinfo.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/prep.h"
+#include "optimizer/tlist.h"
+#include "parser/parse_coerce.h"
+#include "parser/parsetree.h"
+#include "utils/rel.h"
+
+static List *expand_insert_targetlist(List *tlist, Relation rel);
+
+
+/*
+ * preprocess_targetlist
+ *	  Driver for preprocessing the parse tree targetlist.
+ *
+ * The preprocessed targetlist is returned in root->processed_tlist.
+ * Also, if this is an UPDATE, we return a list of target column numbers
+ * in root->update_colnos.  (Resnos in processed_tlist will be consecutive,
+ * so do not look at that to find out which columns are targets!)
+ */
+void
+preprocess_targetlist(PlannerInfo *root)
+{
+	Query	   *parse = root->parse;
+	int			result_relation = parse->resultRelation;
+	List	   *range_table = parse->rtable;
+	CmdType		command_type = parse->commandType;
+	RangeTblEntry *target_rte = NULL;
+	Relation	target_relation = NULL;
+	List	   *tlist;
+	ListCell   *lc;
+
+	/*
+	 * If there is a result relation, open it so we can look for missing
+	 * columns and so on.  We assume that previous code already acquired at
+	 * least AccessShareLock on the relation, so we need no lock here.
+	 */
+	if (result_relation)
+	{
+		target_rte = rt_fetch(result_relation, range_table);
+
+		/*
+		 * Sanity check: it'd better be a real relation not, say, a subquery.
+		 * Else parser or rewriter messed up.
+		 */
+		if (target_rte->rtekind != RTE_RELATION)
+			elog(ERROR, "result relation must be a regular relation");
+
+		target_relation = table_open(target_rte->relid, NoLock);
+	}
+	else
+		Assert(command_type == CMD_SELECT);
+
+	/*
+	 * In an INSERT, the executor expects the targetlist to match the exact
+	 * order of the target table's attributes, including entries for
+	 * attributes not mentioned in the source query.
+	 *
+	 * In an UPDATE, we don't rearrange the tlist order, but we need to make a
+	 * separate list of the target attribute numbers, in tlist order, and then
+	 * renumber the processed_tlist entries to be consecutive.
+	 */
+	tlist = parse->targetList;
+	if (command_type == CMD_INSERT)
+		tlist = expand_insert_targetlist(tlist, target_relation);
+	else if (command_type == CMD_UPDATE)
+		root->update_colnos = extract_update_targetlist_colnos(tlist);
+
+	/*
+	 * For non-inherited UPDATE/DELETE, register any junk column(s) needed to
+	 * allow the executor to identify the rows to be updated or deleted.  In
+	 * the inheritance case, we do nothing now, leaving this to be dealt with
+	 * when expand_inherited_rtentry() makes the leaf target relations.  (But
+	 * there might not be any leaf target relations, in which case we must do
+	 * this in distribute_row_identity_vars().)
+	 */
+	if ((command_type == CMD_UPDATE || command_type == CMD_DELETE) &&
+		!target_rte->inh)
+	{
+		/* row-identity logic expects to add stuff to processed_tlist */
+		root->processed_tlist = tlist;
+		add_row_identity_columns(root, result_relation,
+								 target_rte, target_relation);
+		tlist = root->processed_tlist;
+	}
+
+	/*
+	 * Add necessary junk columns for rowmarked rels.  These values are needed
+	 * for locking of rels selected FOR UPDATE/SHARE, and to do EvalPlanQual
+	 * rechecking.  See comments for PlanRowMark in plannodes.h.  If you
+	 * change this stanza, see also expand_inherited_rtentry(), which has to
+	 * be able to add on junk columns equivalent to these.
+	 *
+	 * (Someday it might be useful to fold these resjunk columns into the
+	 * row-identity-column management used for UPDATE/DELETE.  Today is not
+	 * that day, however.  One notable issue is that it seems important that
+	 * the whole-row Vars made here use the real table rowtype, not RECORD, so
+	 * that conversion to/from child relations' rowtypes will happen.  Also,
+	 * since these entries don't potentially bloat with more and more child
+	 * relations, there's not really much need for column sharing.)
+	 */
+	foreach(lc, root->rowMarks)
+	{
+		PlanRowMark *rc = (PlanRowMark *) lfirst(lc);
+		Var		   *var;
+		char		resname[32];
+		TargetEntry *tle;
+
+		/* child rels use the same junk attrs as their parents */
+		if (rc->rti != rc->prti)
+			continue;
+
+		if (rc->allMarkTypes & ~(1 << ROW_MARK_COPY))
+		{
+			/* Need to fetch TID */
+			var = makeVar(rc->rti,
+						  SelfItemPointerAttributeNumber,
+						  TIDOID,
+						  -1,
+						  InvalidOid,
+						  0);
+			snprintf(resname, sizeof(resname), "ctid%u", rc->rowmarkId);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(tlist) + 1,
+								  pstrdup(resname),
+								  true);
+			tlist = lappend(tlist, tle);
+		}
+		if (rc->allMarkTypes & (1 << ROW_MARK_COPY))
+		{
+			/* Need the whole row as a junk var */
+			var = makeWholeRowVar(rt_fetch(rc->rti, range_table),
+								  rc->rti,
+								  0,
+								  false);
+			snprintf(resname, sizeof(resname), "wholerow%u", rc->rowmarkId);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(tlist) + 1,
+								  pstrdup(resname),
+								  true);
+			tlist = lappend(tlist, tle);
+		}
+
+		/* If parent of inheritance tree, always fetch the tableoid too. */
+		if (rc->isParent)
+		{
+			var = makeVar(rc->rti,
+						  TableOidAttributeNumber,
+						  OIDOID,
+						  -1,
+						  InvalidOid,
+						  0);
+			snprintf(resname, sizeof(resname), "tableoid%u", rc->rowmarkId);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(tlist) + 1,
+								  pstrdup(resname),
+								  true);
+			tlist = lappend(tlist, tle);
+		}
+	}
+
+	/*
+	 * If the query has a RETURNING list, add resjunk entries for any Vars
+	 * used in RETURNING that belong to other relations.  We need to do this
+	 * to make these Vars available for the RETURNING calculation.  Vars that
+	 * belong to the result rel don't need to be added, because they will be
+	 * made to refer to the actual heap tuple.
+	 */
+	if (parse->returningList && list_length(parse->rtable) > 1)
+	{
+		List	   *vars;
+		ListCell   *l;
+
+		vars = pull_var_clause((Node *) parse->returningList,
+							   PVC_RECURSE_AGGREGATES |
+							   PVC_RECURSE_WINDOWFUNCS |
+							   PVC_INCLUDE_PLACEHOLDERS);
+		foreach(l, vars)
+		{
+			Var		   *var = (Var *) lfirst(l);
+			TargetEntry *tle;
+
+			if (IsA(var, Var) &&
+				var->varno == result_relation)
+				continue;		/* don't need it */
+
+			if (tlist_member((Expr *) var, tlist))
+				continue;		/* already got it */
+
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(tlist) + 1,
+								  NULL,
+								  true);
+
+			tlist = lappend(tlist, tle);
+		}
+		list_free(vars);
+	}
+
+	root->processed_tlist = tlist;
+
+	if (target_relation)
+		table_close(target_relation, NoLock);
+}
+
+/*
+ * extract_update_targetlist_colnos
+ * 		Extract a list of the target-table column numbers that
+ * 		an UPDATE's targetlist wants to assign to, then renumber.
+ *
+ * The convention in the parser and rewriter is that the resnos in an
+ * UPDATE's non-resjunk TLE entries are the target column numbers
+ * to assign to.  Here, we extract that info into a separate list, and
+ * then convert the tlist to the sequential-numbering convention that's
+ * used by all other query types.
+ *
+ * This is also applied to the tlist associated with INSERT ... ON CONFLICT
+ * ... UPDATE, although not till much later in planning.
+ */
+List *
+extract_update_targetlist_colnos(List *tlist)
+{
+	List	   *update_colnos = NIL;
+	AttrNumber	nextresno = 1;
+	ListCell   *lc;
+
+	foreach(lc, tlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(lc);
+
+		if (!tle->resjunk)
+			update_colnos = lappend_int(update_colnos, tle->resno);
+		tle->resno = nextresno++;
+	}
+	return update_colnos;
+}
+
+
+/*****************************************************************************
+ *
+ *		TARGETLIST EXPANSION
+ *
+ *****************************************************************************/
+
+/*
+ * expand_insert_targetlist
+ *	  Given a target list as generated by the parser and a result relation,
+ *	  add targetlist entries for any missing attributes, and ensure the
+ *	  non-junk attributes appear in proper field order.
+ *
+ * Once upon a time we also did more or less this with UPDATE targetlists,
+ * but now this code is only applied to INSERT targetlists.
+ */
+static List *
+expand_insert_targetlist(List *tlist, Relation rel)
+{
+	List	   *new_tlist = NIL;
+	ListCell   *tlist_item;
+	int			attrno,
+				numattrs;
+
+	tlist_item = list_head(tlist);
+
+	/*
+	 * The rewriter should have already ensured that the TLEs are in correct
+	 * order; but we have to insert TLEs for any missing attributes.
+	 *
+	 * Scan the tuple description in the relation's relcache entry to make
+	 * sure we have all the user attributes in the right order.
+	 */
+	numattrs = RelationGetNumberOfAttributes(rel);
+
+	for (attrno = 1; attrno <= numattrs; attrno++)
+	{
+		Form_pg_attribute att_tup = TupleDescAttr(rel->rd_att, attrno - 1);
+		TargetEntry *new_tle = NULL;
+
+		if (tlist_item != NULL)
+		{
+			TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
+
+			if (!old_tle->resjunk && old_tle->resno == attrno)
+			{
+				new_tle = old_tle;
+				tlist_item = lnext(tlist, tlist_item);
+			}
+		}
+
+		if (new_tle == NULL)
+		{
+			/*
+			 * Didn't find a matching tlist entry, so make one.
+			 *
+			 * INSERTs should insert NULL in this case.  (We assume the
+			 * rewriter would have inserted any available non-NULL default
+			 * value.)  Also, if the column isn't dropped, apply any domain
+			 * constraints that might exist --- this is to catch domain NOT
+			 * NULL.
+			 *
+			 * When generating a NULL constant for a dropped column, we label
+			 * it INT4 (any other guaranteed-to-exist datatype would do as
+			 * well). We can't label it with the dropped column's datatype
+			 * since that might not exist anymore.  It does not really matter
+			 * what we claim the type is, since NULL is NULL --- its
+			 * representation is datatype-independent.  This could perhaps
+			 * confuse code comparing the finished plan to the target
+			 * relation, however.
+			 */
+			Oid			atttype = att_tup->atttypid;
+			Oid			attcollation = att_tup->attcollation;
+			Node	   *new_expr;
+
+			if (!att_tup->attisdropped)
+			{
+				new_expr = (Node *) makeConst(atttype,
+											  -1,
+											  attcollation,
+											  att_tup->attlen,
+											  (Datum) 0,
+											  true, /* isnull */
+											  att_tup->attbyval);
+				new_expr = coerce_to_domain(new_expr,
+											InvalidOid, -1,
+											atttype,
+											COERCION_IMPLICIT,
+											COERCE_IMPLICIT_CAST,
+											-1,
+											false);
+			}
+			else
+			{
+				/* Insert NULL for dropped column */
+				new_expr = (Node *) makeConst(INT4OID,
+											  -1,
+											  InvalidOid,
+											  sizeof(int32),
+											  (Datum) 0,
+											  true, /* isnull */
+											  true /* byval */ );
+			}
+
+			new_tle = makeTargetEntry((Expr *) new_expr,
+									  attrno,
+									  pstrdup(NameStr(att_tup->attname)),
+									  false);
+		}
+
+		new_tlist = lappend(new_tlist, new_tle);
+	}
+
+	/*
+	 * The remaining tlist entries should be resjunk; append them all to the
+	 * end of the new tlist, making sure they have resnos higher than the last
+	 * real attribute.  (Note: although the rewriter already did such
+	 * renumbering, we have to do it again here in case we added NULL entries
+	 * above.)
+	 */
+	while (tlist_item)
+	{
+		TargetEntry *old_tle = (TargetEntry *) lfirst(tlist_item);
+
+		if (!old_tle->resjunk)
+			elog(ERROR, "targetlist is not sorted correctly");
+		/* Get the resno right, but don't copy unnecessarily */
+		if (old_tle->resno != attrno)
+		{
+			old_tle = flatCopyTargetEntry(old_tle);
+			old_tle->resno = attrno;
+		}
+		new_tlist = lappend(new_tlist, old_tle);
+		attrno++;
+		tlist_item = lnext(tlist, tlist_item);
+	}
+
+	return new_tlist;
+}
+
+
+/*
+ * Locate PlanRowMark for given RT index, or return NULL if none
+ *
+ * This probably ought to be elsewhere, but there's no very good place
+ */
+PlanRowMark *
+get_plan_rowmark(List *rowmarks, Index rtindex)
+{
+	ListCell   *l;
+
+	foreach(l, rowmarks)
+	{
+		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
+
+		if (rc->rti == rtindex)
+			return rc;
+	}
+	return NULL;
+}
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
new file mode 100644
index 0000000..e9256a2
--- /dev/null
+++ b/src/backend/optimizer/prep/prepunion.c
@@ -0,0 +1,1420 @@
+/*-------------------------------------------------------------------------
+ *
+ * prepunion.c
+ *	  Routines to plan set-operation queries.  The filename is a leftover
+ *	  from a time when only UNIONs were implemented.
+ *
+ * There are two code paths in the planner for set-operation queries.
+ * If a subquery consists entirely of simple UNION ALL operations, it
+ * is converted into an "append relation".  Otherwise, it is handled
+ * by the general code in this module (plan_set_operations and its
+ * subroutines).  There is some support code here for the append-relation
+ * case, but most of the heavy lifting for that is done elsewhere,
+ * notably in prepjointree.c and allpaths.c.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/prep/prepunion.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "access/sysattr.h"
+#include "catalog/partition.h"
+#include "catalog/pg_inherits.h"
+#include "catalog/pg_type.h"
+#include "miscadmin.h"
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/cost.h"
+#include "optimizer/pathnode.h"
+#include "optimizer/paths.h"
+#include "optimizer/planmain.h"
+#include "optimizer/planner.h"
+#include "optimizer/prep.h"
+#include "optimizer/tlist.h"
+#include "parser/parse_coerce.h"
+#include "parser/parsetree.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/selfuncs.h"
+#include "utils/syscache.h"
+
+
+static RelOptInfo *recurse_set_operations(Node *setOp, PlannerInfo *root,
+										  List *colTypes, List *colCollations,
+										  bool junkOK,
+										  int flag, List *refnames_tlist,
+										  List **pTargetList,
+										  double *pNumGroups);
+static RelOptInfo *generate_recursion_path(SetOperationStmt *setOp,
+										   PlannerInfo *root,
+										   List *refnames_tlist,
+										   List **pTargetList);
+static RelOptInfo *generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
+										List *refnames_tlist,
+										List **pTargetList);
+static RelOptInfo *generate_nonunion_paths(SetOperationStmt *op, PlannerInfo *root,
+										   List *refnames_tlist,
+										   List **pTargetList);
+static List *plan_union_children(PlannerInfo *root,
+								 SetOperationStmt *top_union,
+								 List *refnames_tlist,
+								 List **tlist_list);
+static Path *make_union_unique(SetOperationStmt *op, Path *path, List *tlist,
+							   PlannerInfo *root);
+static void postprocess_setop_rel(PlannerInfo *root, RelOptInfo *rel);
+static bool choose_hashed_setop(PlannerInfo *root, List *groupClauses,
+								Path *input_path,
+								double dNumGroups, double dNumOutputRows,
+								const char *construct);
+static List *generate_setop_tlist(List *colTypes, List *colCollations,
+								  int flag,
+								  Index varno,
+								  bool hack_constants,
+								  List *input_tlist,
+								  List *refnames_tlist);
+static List *generate_append_tlist(List *colTypes, List *colCollations,
+								   bool flag,
+								   List *input_tlists,
+								   List *refnames_tlist);
+static List *generate_setop_grouplist(SetOperationStmt *op, List *targetlist);
+
+
+/*
+ * plan_set_operations
+ *
+ *	  Plans the queries for a tree of set operations (UNION/INTERSECT/EXCEPT)
+ *
+ * This routine only deals with the setOperations tree of the given query.
+ * Any top-level ORDER BY requested in root->parse->sortClause will be handled
+ * when we return to grouping_planner; likewise for LIMIT.
+ *
+ * What we return is an "upperrel" RelOptInfo containing at least one Path
+ * that implements the set-operation tree.  In addition, root->processed_tlist
+ * receives a targetlist representing the output of the topmost setop node.
+ */
+RelOptInfo *
+plan_set_operations(PlannerInfo *root)
+{
+	Query	   *parse = root->parse;
+	SetOperationStmt *topop = castNode(SetOperationStmt, parse->setOperations);
+	Node	   *node;
+	RangeTblEntry *leftmostRTE;
+	Query	   *leftmostQuery;
+	RelOptInfo *setop_rel;
+	List	   *top_tlist;
+
+	Assert(topop);
+
+	/* check for unsupported stuff */
+	Assert(parse->jointree->fromlist == NIL);
+	Assert(parse->jointree->quals == NULL);
+	Assert(parse->groupClause == NIL);
+	Assert(parse->havingQual == NULL);
+	Assert(parse->windowClause == NIL);
+	Assert(parse->distinctClause == NIL);
+
+	/*
+	 * In the outer query level, we won't have any true equivalences to deal
+	 * with; but we do want to be able to make pathkeys, which will require
+	 * single-member EquivalenceClasses.  Indicate that EC merging is complete
+	 * so that pathkeys.c won't complain.
+	 */
+	Assert(root->eq_classes == NIL);
+	root->ec_merging_done = true;
+
+	/*
+	 * We'll need to build RelOptInfos for each of the leaf subqueries, which
+	 * are RTE_SUBQUERY rangetable entries in this Query.  Prepare the index
+	 * arrays for those, and for AppendRelInfos in case they're needed.
+	 */
+	setup_simple_rel_arrays(root);
+
+	/*
+	 * Find the leftmost component Query.  We need to use its column names for
+	 * all generated tlists (else SELECT INTO won't work right).
+	 */
+	node = topop->larg;
+	while (node && IsA(node, SetOperationStmt))
+		node = ((SetOperationStmt *) node)->larg;
+	Assert(node && IsA(node, RangeTblRef));
+	leftmostRTE = root->simple_rte_array[((RangeTblRef *) node)->rtindex];
+	leftmostQuery = leftmostRTE->subquery;
+	Assert(leftmostQuery != NULL);
+
+	/*
+	 * If the topmost node is a recursive union, it needs special processing.
+	 */
+	if (root->hasRecursion)
+	{
+		setop_rel = generate_recursion_path(topop, root,
+											leftmostQuery->targetList,
+											&top_tlist);
+	}
+	else
+	{
+		/*
+		 * Recurse on setOperations tree to generate paths for set ops. The
+		 * final output paths should have just the column types shown as the
+		 * output from the top-level node, plus possibly resjunk working
+		 * columns (we can rely on upper-level nodes to deal with that).
+		 */
+		setop_rel = recurse_set_operations((Node *) topop, root,
+										   topop->colTypes, topop->colCollations,
+										   true, -1,
+										   leftmostQuery->targetList,
+										   &top_tlist,
+										   NULL);
+	}
+
+	/* Must return the built tlist into root->processed_tlist. */
+	root->processed_tlist = top_tlist;
+
+	return setop_rel;
+}
+
+/*
+ * recurse_set_operations
+ *	  Recursively handle one step in a tree of set operations
+ *
+ * colTypes: OID list of set-op's result column datatypes
+ * colCollations: OID list of set-op's result column collations
+ * junkOK: if true, child resjunk columns may be left in the result
+ * flag: if >= 0, add a resjunk output column indicating value of flag
+ * refnames_tlist: targetlist to take column names from
+ *
+ * Returns a RelOptInfo for the subtree, as well as these output parameters:
+ * *pTargetList: receives the fully-fledged tlist for the subtree's top plan
+ * *pNumGroups: if not NULL, we estimate the number of distinct groups
+ *		in the result, and store it there
+ *
+ * The pTargetList output parameter is mostly redundant with the pathtarget
+ * of the returned RelOptInfo, but for the moment we need it because much of
+ * the logic in this file depends on flag columns being marked resjunk.
+ * Pending a redesign of how that works, this is the easy way out.
+ *
+ * We don't have to care about typmods here: the only allowed difference
+ * between set-op input and output typmods is input is a specific typmod
+ * and output is -1, and that does not require a coercion.
+ */
+static RelOptInfo *
+recurse_set_operations(Node *setOp, PlannerInfo *root,
+					   List *colTypes, List *colCollations,
+					   bool junkOK,
+					   int flag, List *refnames_tlist,
+					   List **pTargetList,
+					   double *pNumGroups)
+{
+	RelOptInfo *rel = NULL;		/* keep compiler quiet */
+
+	/* Guard against stack overflow due to overly complex setop nests */
+	check_stack_depth();
+
+	if (IsA(setOp, RangeTblRef))
+	{
+		RangeTblRef *rtr = (RangeTblRef *) setOp;
+		RangeTblEntry *rte = root->simple_rte_array[rtr->rtindex];
+		Query	   *subquery = rte->subquery;
+		PlannerInfo *subroot;
+		RelOptInfo *final_rel;
+		Path	   *subpath;
+		Path	   *path;
+		List	   *tlist;
+
+		Assert(subquery != NULL);
+
+		/* Build a RelOptInfo for this leaf subquery. */
+		rel = build_simple_rel(root, rtr->rtindex, NULL);
+
+		/* plan_params should not be in use in current query level */
+		Assert(root->plan_params == NIL);
+
+		/* Generate a subroot and Paths for the subquery */
+		subroot = rel->subroot = subquery_planner(root->glob, subquery,
+												  root,
+												  false,
+												  root->tuple_fraction);
+
+		/*
+		 * It should not be possible for the primitive query to contain any
+		 * cross-references to other primitive queries in the setop tree.
+		 */
+		if (root->plan_params)
+			elog(ERROR, "unexpected outer reference in set operation subquery");
+
+		/* Figure out the appropriate target list for this subquery. */
+		tlist = generate_setop_tlist(colTypes, colCollations,
+									 flag,
+									 rtr->rtindex,
+									 true,
+									 subroot->processed_tlist,
+									 refnames_tlist);
+		rel->reltarget = create_pathtarget(root, tlist);
+
+		/* Return the fully-fledged tlist to caller, too */
+		*pTargetList = tlist;
+
+		/*
+		 * Mark rel with estimated output rows, width, etc.  Note that we have
+		 * to do this before generating outer-query paths, else
+		 * cost_subqueryscan is not happy.
+		 */
+		set_subquery_size_estimates(root, rel);
+
+		/*
+		 * Since we may want to add a partial path to this relation, we must
+		 * set its consider_parallel flag correctly.
+		 */
+		final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
+		rel->consider_parallel = final_rel->consider_parallel;
+
+		/*
+		 * For the moment, we consider only a single Path for the subquery.
+		 * This should change soon (make it look more like
+		 * set_subquery_pathlist).
+		 */
+		subpath = get_cheapest_fractional_path(final_rel,
+											   root->tuple_fraction);
+
+		/*
+		 * Stick a SubqueryScanPath atop that.
+		 *
+		 * We don't bother to determine the subquery's output ordering since
+		 * it won't be reflected in the set-op result anyhow; so just label
+		 * the SubqueryScanPath with nil pathkeys.  (XXX that should change
+		 * soon too, likely.)
+		 */
+		path = (Path *) create_subqueryscan_path(root, rel, subpath,
+												 NIL, NULL);
+
+		add_path(rel, path);
+
+		/*
+		 * If we have a partial path for the child relation, we can use that
+		 * to build a partial path for this relation.  But there's no point in
+		 * considering any path but the cheapest.
+		 */
+		if (rel->consider_parallel && bms_is_empty(rel->lateral_relids) &&
+			final_rel->partial_pathlist != NIL)
+		{
+			Path	   *partial_subpath;
+			Path	   *partial_path;
+
+			partial_subpath = linitial(final_rel->partial_pathlist);
+			partial_path = (Path *)
+				create_subqueryscan_path(root, rel, partial_subpath,
+										 NIL, NULL);
+			add_partial_path(rel, partial_path);
+		}
+
+		/*
+		 * Estimate number of groups if caller wants it.  If the subquery used
+		 * grouping or aggregation, its output is probably mostly unique
+		 * anyway; otherwise do statistical estimation.
+		 *
+		 * XXX you don't really want to know about this: we do the estimation
+		 * using the subquery's original targetlist expressions, not the
+		 * subroot->processed_tlist which might seem more appropriate.  The
+		 * reason is that if the subquery is itself a setop, it may return a
+		 * processed_tlist containing "varno 0" Vars generated by
+		 * generate_append_tlist, and those would confuse estimate_num_groups
+		 * mightily.  We ought to get rid of the "varno 0" hack, but that
+		 * requires a redesign of the parsetree representation of setops, so
+		 * that there can be an RTE corresponding to each setop's output.
+		 */
+		if (pNumGroups)
+		{
+			if (subquery->groupClause || subquery->groupingSets ||
+				subquery->distinctClause ||
+				subroot->hasHavingQual || subquery->hasAggs)
+				*pNumGroups = subpath->rows;
+			else
+				*pNumGroups = estimate_num_groups(subroot,
+												  get_tlist_exprs(subquery->targetList, false),
+												  subpath->rows,
+												  NULL,
+												  NULL);
+		}
+	}
+	else if (IsA(setOp, SetOperationStmt))
+	{
+		SetOperationStmt *op = (SetOperationStmt *) setOp;
+
+		/* UNIONs are much different from INTERSECT/EXCEPT */
+		if (op->op == SETOP_UNION)
+			rel = generate_union_paths(op, root,
+									   refnames_tlist,
+									   pTargetList);
+		else
+			rel = generate_nonunion_paths(op, root,
+										  refnames_tlist,
+										  pTargetList);
+		if (pNumGroups)
+			*pNumGroups = rel->rows;
+
+		/*
+		 * If necessary, add a Result node to project the caller-requested
+		 * output columns.
+		 *
+		 * XXX you don't really want to know about this: setrefs.c will apply
+		 * fix_upper_expr() to the Result node's tlist. This would fail if the
+		 * Vars generated by generate_setop_tlist() were not exactly equal()
+		 * to the corresponding tlist entries of the subplan. However, since
+		 * the subplan was generated by generate_union_paths() or
+		 * generate_nonunion_paths(), and hence its tlist was generated by
+		 * generate_append_tlist(), this will work.  We just tell
+		 * generate_setop_tlist() to use varno 0.
+		 */
+		if (flag >= 0 ||
+			!tlist_same_datatypes(*pTargetList, colTypes, junkOK) ||
+			!tlist_same_collations(*pTargetList, colCollations, junkOK))
+		{
+			PathTarget *target;
+			ListCell   *lc;
+
+			*pTargetList = generate_setop_tlist(colTypes, colCollations,
+												flag,
+												0,
+												false,
+												*pTargetList,
+												refnames_tlist);
+			target = create_pathtarget(root, *pTargetList);
+
+			/* Apply projection to each path */
+			foreach(lc, rel->pathlist)
+			{
+				Path	   *subpath = (Path *) lfirst(lc);
+				Path	   *path;
+
+				Assert(subpath->param_info == NULL);
+				path = apply_projection_to_path(root, subpath->parent,
+												subpath, target);
+				/* If we had to add a Result, path is different from subpath */
+				if (path != subpath)
+					lfirst(lc) = path;
+			}
+
+			/* Apply projection to each partial path */
+			foreach(lc, rel->partial_pathlist)
+			{
+				Path	   *subpath = (Path *) lfirst(lc);
+				Path	   *path;
+
+				Assert(subpath->param_info == NULL);
+
+				/* avoid apply_projection_to_path, in case of multiple refs */
+				path = (Path *) create_projection_path(root, subpath->parent,
+													   subpath, target);
+				lfirst(lc) = path;
+			}
+		}
+	}
+	else
+	{
+		elog(ERROR, "unrecognized node type: %d",
+			 (int) nodeTag(setOp));
+		*pTargetList = NIL;
+	}
+
+	postprocess_setop_rel(root, rel);
+
+	return rel;
+}
+
+/*
+ * Generate paths for a recursive UNION node
+ */
+static RelOptInfo *
+generate_recursion_path(SetOperationStmt *setOp, PlannerInfo *root,
+						List *refnames_tlist,
+						List **pTargetList)
+{
+	RelOptInfo *result_rel;
+	Path	   *path;
+	RelOptInfo *lrel,
+			   *rrel;
+	Path	   *lpath;
+	Path	   *rpath;
+	List	   *lpath_tlist;
+	List	   *rpath_tlist;
+	List	   *tlist;
+	List	   *groupList;
+	double		dNumGroups;
+
+	/* Parser should have rejected other cases */
+	if (setOp->op != SETOP_UNION)
+		elog(ERROR, "only UNION queries can be recursive");
+	/* Worktable ID should be assigned */
+	Assert(root->wt_param_id >= 0);
+
+	/*
+	 * Unlike a regular UNION node, process the left and right inputs
+	 * separately without any intention of combining them into one Append.
+	 */
+	lrel = recurse_set_operations(setOp->larg, root,
+								  setOp->colTypes, setOp->colCollations,
+								  false, -1,
+								  refnames_tlist,
+								  &lpath_tlist,
+								  NULL);
+	lpath = lrel->cheapest_total_path;
+	/* The right path will want to look at the left one ... */
+	root->non_recursive_path = lpath;
+	rrel = recurse_set_operations(setOp->rarg, root,
+								  setOp->colTypes, setOp->colCollations,
+								  false, -1,
+								  refnames_tlist,
+								  &rpath_tlist,
+								  NULL);
+	rpath = rrel->cheapest_total_path;
+	root->non_recursive_path = NULL;
+
+	/*
+	 * Generate tlist for RecursiveUnion path node --- same as in Append cases
+	 */
+	tlist = generate_append_tlist(setOp->colTypes, setOp->colCollations, false,
+								  list_make2(lpath_tlist, rpath_tlist),
+								  refnames_tlist);
+
+	*pTargetList = tlist;
+
+	/* Build result relation. */
+	result_rel = fetch_upper_rel(root, UPPERREL_SETOP,
+								 bms_union(lrel->relids, rrel->relids));
+	result_rel->reltarget = create_pathtarget(root, tlist);
+
+	/*
+	 * If UNION, identify the grouping operators
+	 */
+	if (setOp->all)
+	{
+		groupList = NIL;
+		dNumGroups = 0;
+	}
+	else
+	{
+		/* Identify the grouping semantics */
+		groupList = generate_setop_grouplist(setOp, tlist);
+
+		/* We only support hashing here */
+		if (!grouping_is_hashable(groupList))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("could not implement recursive UNION"),
+					 errdetail("All column datatypes must be hashable.")));
+
+		/*
+		 * For the moment, take the number of distinct groups as equal to the
+		 * total input size, ie, the worst case.
+		 */
+		dNumGroups = lpath->rows + rpath->rows * 10;
+	}
+
+	/*
+	 * And make the path node.
+	 */
+	path = (Path *) create_recursiveunion_path(root,
+											   result_rel,
+											   lpath,
+											   rpath,
+											   result_rel->reltarget,
+											   groupList,
+											   root->wt_param_id,
+											   dNumGroups);
+
+	add_path(result_rel, path);
+	postprocess_setop_rel(root, result_rel);
+	return result_rel;
+}
+
+/*
+ * Generate paths for a UNION or UNION ALL node
+ */
+static RelOptInfo *
+generate_union_paths(SetOperationStmt *op, PlannerInfo *root,
+					 List *refnames_tlist,
+					 List **pTargetList)
+{
+	Relids		relids = NULL;
+	RelOptInfo *result_rel;
+	double		save_fraction = root->tuple_fraction;
+	ListCell   *lc;
+	List	   *pathlist = NIL;
+	List	   *partial_pathlist = NIL;
+	bool		partial_paths_valid = true;
+	bool		consider_parallel = true;
+	List	   *rellist;
+	List	   *tlist_list;
+	List	   *tlist;
+	Path	   *path;
+
+	/*
+	 * If plain UNION, tell children to fetch all tuples.
+	 *
+	 * Note: in UNION ALL, we pass the top-level tuple_fraction unmodified to
+	 * each arm of the UNION ALL.  One could make a case for reducing the
+	 * tuple fraction for later arms (discounting by the expected size of the
+	 * earlier arms' results) but it seems not worth the trouble. The normal
+	 * case where tuple_fraction isn't already zero is a LIMIT at top level,
+	 * and passing it down as-is is usually enough to get the desired result
+	 * of preferring fast-start plans.
+	 */
+	if (!op->all)
+		root->tuple_fraction = 0.0;
+
+	/*
+	 * If any of my children are identical UNION nodes (same op, all-flag, and
+	 * colTypes) then they can be merged into this node so that we generate
+	 * only one Append and unique-ification for the lot.  Recurse to find such
+	 * nodes and compute their children's paths.
+	 */
+	rellist = plan_union_children(root, op, refnames_tlist, &tlist_list);
+
+	/*
+	 * Generate tlist for Append plan node.
+	 *
+	 * The tlist for an Append plan isn't important as far as the Append is
+	 * concerned, but we must make it look real anyway for the benefit of the
+	 * next plan level up.
+	 */
+	tlist = generate_append_tlist(op->colTypes, op->colCollations, false,
+								  tlist_list, refnames_tlist);
+
+	*pTargetList = tlist;
+
+	/* Build path lists and relid set. */
+	foreach(lc, rellist)
+	{
+		RelOptInfo *rel = lfirst(lc);
+
+		pathlist = lappend(pathlist, rel->cheapest_total_path);
+
+		if (consider_parallel)
+		{
+			if (!rel->consider_parallel)
+			{
+				consider_parallel = false;
+				partial_paths_valid = false;
+			}
+			else if (rel->partial_pathlist == NIL)
+				partial_paths_valid = false;
+			else
+				partial_pathlist = lappend(partial_pathlist,
+										   linitial(rel->partial_pathlist));
+		}
+
+		relids = bms_union(relids, rel->relids);
+	}
+
+	/* Build result relation. */
+	result_rel = fetch_upper_rel(root, UPPERREL_SETOP, relids);
+	result_rel->reltarget = create_pathtarget(root, tlist);
+	result_rel->consider_parallel = consider_parallel;
+
+	/*
+	 * Append the child results together.
+	 */
+	path = (Path *) create_append_path(root, result_rel, pathlist, NIL,
+									   NIL, NULL, 0, false, -1);
+
+	/*
+	 * For UNION ALL, we just need the Append path.  For UNION, need to add
+	 * node(s) to remove duplicates.
+	 */
+	if (!op->all)
+		path = make_union_unique(op, path, tlist, root);
+
+	add_path(result_rel, path);
+
+	/*
+	 * Estimate number of groups.  For now we just assume the output is unique
+	 * --- this is certainly true for the UNION case, and we want worst-case
+	 * estimates anyway.
+	 */
+	result_rel->rows = path->rows;
+
+	/*
+	 * Now consider doing the same thing using the partial paths plus Append
+	 * plus Gather.
+	 */
+	if (partial_paths_valid)
+	{
+		Path	   *ppath;
+		ListCell   *lc;
+		int			parallel_workers = 0;
+
+		/* Find the highest number of workers requested for any subpath. */
+		foreach(lc, partial_pathlist)
+		{
+			Path	   *path = lfirst(lc);
+
+			parallel_workers = Max(parallel_workers, path->parallel_workers);
+		}
+		Assert(parallel_workers > 0);
+
+		/*
+		 * If the use of parallel append is permitted, always request at least
+		 * log2(# of children) paths.  We assume it can be useful to have
+		 * extra workers in this case because they will be spread out across
+		 * the children.  The precise formula is just a guess; see
+		 * add_paths_to_append_rel.
+		 */
+		if (enable_parallel_append)
+		{
+			parallel_workers = Max(parallel_workers,
+								   fls(list_length(partial_pathlist)));
+			parallel_workers = Min(parallel_workers,
+								   max_parallel_workers_per_gather);
+		}
+		Assert(parallel_workers > 0);
+
+		ppath = (Path *)
+			create_append_path(root, result_rel, NIL, partial_pathlist,
+							   NIL, NULL,
+							   parallel_workers, enable_parallel_append,
+							   -1);
+		ppath = (Path *)
+			create_gather_path(root, result_rel, ppath,
+							   result_rel->reltarget, NULL, NULL);
+		if (!op->all)
+			ppath = make_union_unique(op, ppath, tlist, root);
+		add_path(result_rel, ppath);
+	}
+
+	/* Undo effects of possibly forcing tuple_fraction to 0 */
+	root->tuple_fraction = save_fraction;
+
+	return result_rel;
+}
+
+/*
+ * Generate paths for an INTERSECT, INTERSECT ALL, EXCEPT, or EXCEPT ALL node
+ */
+static RelOptInfo *
+generate_nonunion_paths(SetOperationStmt *op, PlannerInfo *root,
+						List *refnames_tlist,
+						List **pTargetList)
+{
+	RelOptInfo *result_rel;
+	RelOptInfo *lrel,
+			   *rrel;
+	double		save_fraction = root->tuple_fraction;
+	Path	   *lpath,
+			   *rpath,
+			   *path;
+	List	   *lpath_tlist,
+			   *rpath_tlist,
+			   *tlist_list,
+			   *tlist,
+			   *groupList,
+			   *pathlist;
+	double		dLeftGroups,
+				dRightGroups,
+				dNumGroups,
+				dNumOutputRows;
+	bool		use_hash;
+	SetOpCmd	cmd;
+	int			firstFlag;
+
+	/*
+	 * Tell children to fetch all tuples.
+	 */
+	root->tuple_fraction = 0.0;
+
+	/* Recurse on children, ensuring their outputs are marked */
+	lrel = recurse_set_operations(op->larg, root,
+								  op->colTypes, op->colCollations,
+								  false, 0,
+								  refnames_tlist,
+								  &lpath_tlist,
+								  &dLeftGroups);
+	lpath = lrel->cheapest_total_path;
+	rrel = recurse_set_operations(op->rarg, root,
+								  op->colTypes, op->colCollations,
+								  false, 1,
+								  refnames_tlist,
+								  &rpath_tlist,
+								  &dRightGroups);
+	rpath = rrel->cheapest_total_path;
+
+	/* Undo effects of forcing tuple_fraction to 0 */
+	root->tuple_fraction = save_fraction;
+
+	/*
+	 * For EXCEPT, we must put the left input first.  For INTERSECT, either
+	 * order should give the same results, and we prefer to put the smaller
+	 * input first in order to minimize the size of the hash table in the
+	 * hashing case.  "Smaller" means the one with the fewer groups.
+	 */
+	if (op->op == SETOP_EXCEPT || dLeftGroups <= dRightGroups)
+	{
+		pathlist = list_make2(lpath, rpath);
+		tlist_list = list_make2(lpath_tlist, rpath_tlist);
+		firstFlag = 0;
+	}
+	else
+	{
+		pathlist = list_make2(rpath, lpath);
+		tlist_list = list_make2(rpath_tlist, lpath_tlist);
+		firstFlag = 1;
+	}
+
+	/*
+	 * Generate tlist for Append plan node.
+	 *
+	 * The tlist for an Append plan isn't important as far as the Append is
+	 * concerned, but we must make it look real anyway for the benefit of the
+	 * next plan level up.  In fact, it has to be real enough that the flag
+	 * column is shown as a variable not a constant, else setrefs.c will get
+	 * confused.
+	 */
+	tlist = generate_append_tlist(op->colTypes, op->colCollations, true,
+								  tlist_list, refnames_tlist);
+
+	*pTargetList = tlist;
+
+	/* Build result relation. */
+	result_rel = fetch_upper_rel(root, UPPERREL_SETOP,
+								 bms_union(lrel->relids, rrel->relids));
+	result_rel->reltarget = create_pathtarget(root, tlist);
+
+	/*
+	 * Append the child results together.
+	 */
+	path = (Path *) create_append_path(root, result_rel, pathlist, NIL,
+									   NIL, NULL, 0, false, -1);
+
+	/* Identify the grouping semantics */
+	groupList = generate_setop_grouplist(op, tlist);
+
+	/*
+	 * Estimate number of distinct groups that we'll need hashtable entries
+	 * for; this is the size of the left-hand input for EXCEPT, or the smaller
+	 * input for INTERSECT.  Also estimate the number of eventual output rows.
+	 * In non-ALL cases, we estimate each group produces one output row; in
+	 * ALL cases use the relevant relation size.  These are worst-case
+	 * estimates, of course, but we need to be conservative.
+	 */
+	if (op->op == SETOP_EXCEPT)
+	{
+		dNumGroups = dLeftGroups;
+		dNumOutputRows = op->all ? lpath->rows : dNumGroups;
+	}
+	else
+	{
+		dNumGroups = Min(dLeftGroups, dRightGroups);
+		dNumOutputRows = op->all ? Min(lpath->rows, rpath->rows) : dNumGroups;
+	}
+
+	/*
+	 * Decide whether to hash or sort, and add a sort node if needed.
+	 */
+	use_hash = choose_hashed_setop(root, groupList, path,
+								   dNumGroups, dNumOutputRows,
+								   (op->op == SETOP_INTERSECT) ? "INTERSECT" : "EXCEPT");
+
+	if (groupList && !use_hash)
+		path = (Path *) create_sort_path(root,
+										 result_rel,
+										 path,
+										 make_pathkeys_for_sortclauses(root,
+																	   groupList,
+																	   tlist),
+										 -1.0);
+
+	/*
+	 * Finally, add a SetOp path node to generate the correct output.
+	 */
+	switch (op->op)
+	{
+		case SETOP_INTERSECT:
+			cmd = op->all ? SETOPCMD_INTERSECT_ALL : SETOPCMD_INTERSECT;
+			break;
+		case SETOP_EXCEPT:
+			cmd = op->all ? SETOPCMD_EXCEPT_ALL : SETOPCMD_EXCEPT;
+			break;
+		default:
+			elog(ERROR, "unrecognized set op: %d", (int) op->op);
+			cmd = SETOPCMD_INTERSECT;	/* keep compiler quiet */
+			break;
+	}
+	path = (Path *) create_setop_path(root,
+									  result_rel,
+									  path,
+									  cmd,
+									  use_hash ? SETOP_HASHED : SETOP_SORTED,
+									  groupList,
+									  list_length(op->colTypes) + 1,
+									  use_hash ? firstFlag : -1,
+									  dNumGroups,
+									  dNumOutputRows);
+
+	result_rel->rows = path->rows;
+	add_path(result_rel, path);
+	return result_rel;
+}
+
+/*
+ * Pull up children of a UNION node that are identically-propertied UNIONs.
+ *
+ * NOTE: we can also pull a UNION ALL up into a UNION, since the distinct
+ * output rows will be lost anyway.
+ *
+ * NOTE: currently, we ignore collations while determining if a child has
+ * the same properties.  This is semantically sound only so long as all
+ * collations have the same notion of equality.  It is valid from an
+ * implementation standpoint because we don't care about the ordering of
+ * a UNION child's result: UNION ALL results are always unordered, and
+ * generate_union_paths will force a fresh sort if the top level is a UNION.
+ */
+static List *
+plan_union_children(PlannerInfo *root,
+					SetOperationStmt *top_union,
+					List *refnames_tlist,
+					List **tlist_list)
+{
+	List	   *pending_rels = list_make1(top_union);
+	List	   *result = NIL;
+	List	   *child_tlist;
+
+	*tlist_list = NIL;
+
+	while (pending_rels != NIL)
+	{
+		Node	   *setOp = linitial(pending_rels);
+
+		pending_rels = list_delete_first(pending_rels);
+
+		if (IsA(setOp, SetOperationStmt))
+		{
+			SetOperationStmt *op = (SetOperationStmt *) setOp;
+
+			if (op->op == top_union->op &&
+				(op->all == top_union->all || op->all) &&
+				equal(op->colTypes, top_union->colTypes))
+			{
+				/* Same UNION, so fold children into parent */
+				pending_rels = lcons(op->rarg, pending_rels);
+				pending_rels = lcons(op->larg, pending_rels);
+				continue;
+			}
+		}
+
+		/*
+		 * Not same, so plan this child separately.
+		 *
+		 * Note we disallow any resjunk columns in child results.  This is
+		 * necessary since the Append node that implements the union won't do
+		 * any projection, and upper levels will get confused if some of our
+		 * output tuples have junk and some don't.  This case only arises when
+		 * we have an EXCEPT or INTERSECT as child, else there won't be
+		 * resjunk anyway.
+		 */
+		result = lappend(result, recurse_set_operations(setOp, root,
+														top_union->colTypes,
+														top_union->colCollations,
+														false, -1,
+														refnames_tlist,
+														&child_tlist,
+														NULL));
+		*tlist_list = lappend(*tlist_list, child_tlist);
+	}
+
+	return result;
+}
+
+/*
+ * Add nodes to the given path tree to unique-ify the result of a UNION.
+ */
+static Path *
+make_union_unique(SetOperationStmt *op, Path *path, List *tlist,
+				  PlannerInfo *root)
+{
+	RelOptInfo *result_rel = fetch_upper_rel(root, UPPERREL_SETOP, NULL);
+	List	   *groupList;
+	double		dNumGroups;
+
+	/* Identify the grouping semantics */
+	groupList = generate_setop_grouplist(op, tlist);
+
+	/*
+	 * XXX for the moment, take the number of distinct groups as equal to the
+	 * total input size, ie, the worst case.  This is too conservative, but
+	 * it's not clear how to get a decent estimate of the true size.  One
+	 * should note as well the propensity of novices to write UNION rather
+	 * than UNION ALL even when they don't expect any duplicates...
+	 */
+	dNumGroups = path->rows;
+
+	/* Decide whether to hash or sort */
+	if (choose_hashed_setop(root, groupList, path,
+							dNumGroups, dNumGroups,
+							"UNION"))
+	{
+		/* Hashed aggregate plan --- no sort needed */
+		path = (Path *) create_agg_path(root,
+										result_rel,
+										path,
+										create_pathtarget(root, tlist),
+										AGG_HASHED,
+										AGGSPLIT_SIMPLE,
+										groupList,
+										NIL,
+										NULL,
+										dNumGroups);
+	}
+	else
+	{
+		/* Sort and Unique */
+		if (groupList)
+			path = (Path *)
+				create_sort_path(root,
+								 result_rel,
+								 path,
+								 make_pathkeys_for_sortclauses(root,
+															   groupList,
+															   tlist),
+								 -1.0);
+		path = (Path *) create_upper_unique_path(root,
+												 result_rel,
+												 path,
+												 list_length(path->pathkeys),
+												 dNumGroups);
+	}
+
+	return path;
+}
+
+/*
+ * postprocess_setop_rel - perform steps required after adding paths
+ */
+static void
+postprocess_setop_rel(PlannerInfo *root, RelOptInfo *rel)
+{
+	/*
+	 * We don't currently worry about allowing FDWs to contribute paths to
+	 * this relation, but give extensions a chance.
+	 */
+	if (create_upper_paths_hook)
+		(*create_upper_paths_hook) (root, UPPERREL_SETOP,
+									NULL, rel, NULL);
+
+	/* Select cheapest path */
+	set_cheapest(rel);
+}
+
+/*
+ * choose_hashed_setop - should we use hashing for a set operation?
+ */
+static bool
+choose_hashed_setop(PlannerInfo *root, List *groupClauses,
+					Path *input_path,
+					double dNumGroups, double dNumOutputRows,
+					const char *construct)
+{
+	int			numGroupCols = list_length(groupClauses);
+	Size		hash_mem_limit = get_hash_memory_limit();
+	bool		can_sort;
+	bool		can_hash;
+	Size		hashentrysize;
+	Path		hashed_p;
+	Path		sorted_p;
+	double		tuple_fraction;
+
+	/* Check whether the operators support sorting or hashing */
+	can_sort = grouping_is_sortable(groupClauses);
+	can_hash = grouping_is_hashable(groupClauses);
+	if (can_hash && can_sort)
+	{
+		/* we have a meaningful choice to make, continue ... */
+	}
+	else if (can_hash)
+		return true;
+	else if (can_sort)
+		return false;
+	else
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+		/* translator: %s is UNION, INTERSECT, or EXCEPT */
+				 errmsg("could not implement %s", construct),
+				 errdetail("Some of the datatypes only support hashing, while others only support sorting.")));
+
+	/* Prefer sorting when enable_hashagg is off */
+	if (!enable_hashagg)
+		return false;
+
+	/*
+	 * Don't do it if it doesn't look like the hashtable will fit into
+	 * hash_mem.
+	 */
+	hashentrysize = MAXALIGN(input_path->pathtarget->width) + MAXALIGN(SizeofMinimalTupleHeader);
+
+	if (hashentrysize * dNumGroups > hash_mem_limit)
+		return false;
+
+	/*
+	 * See if the estimated cost is no more than doing it the other way.
+	 *
+	 * We need to consider input_plan + hashagg versus input_plan + sort +
+	 * group.  Note that the actual result plan might involve a SetOp or
+	 * Unique node, not Agg or Group, but the cost estimates for Agg and Group
+	 * should be close enough for our purposes here.
+	 *
+	 * These path variables are dummies that just hold cost fields; we don't
+	 * make actual Paths for these steps.
+	 */
+	cost_agg(&hashed_p, root, AGG_HASHED, NULL,
+			 numGroupCols, dNumGroups,
+			 NIL,
+			 input_path->startup_cost, input_path->total_cost,
+			 input_path->rows, input_path->pathtarget->width);
+
+	/*
+	 * Now for the sorted case.  Note that the input is *always* unsorted,
+	 * since it was made by appending unrelated sub-relations together.
+	 */
+	sorted_p.startup_cost = input_path->startup_cost;
+	sorted_p.total_cost = input_path->total_cost;
+	/* XXX cost_sort doesn't actually look at pathkeys, so just pass NIL */
+	cost_sort(&sorted_p, root, NIL, sorted_p.total_cost,
+			  input_path->rows, input_path->pathtarget->width,
+			  0.0, work_mem, -1.0);
+	cost_group(&sorted_p, root, numGroupCols, dNumGroups,
+			   NIL,
+			   sorted_p.startup_cost, sorted_p.total_cost,
+			   input_path->rows);
+
+	/*
+	 * Now make the decision using the top-level tuple fraction.  First we
+	 * have to convert an absolute count (LIMIT) into fractional form.
+	 */
+	tuple_fraction = root->tuple_fraction;
+	if (tuple_fraction >= 1.0)
+		tuple_fraction /= dNumOutputRows;
+
+	if (compare_fractional_path_costs(&hashed_p, &sorted_p,
+									  tuple_fraction) < 0)
+	{
+		/* Hashed is cheaper, so use it */
+		return true;
+	}
+	return false;
+}
+
+/*
+ * Generate targetlist for a set-operation plan node
+ *
+ * colTypes: OID list of set-op's result column datatypes
+ * colCollations: OID list of set-op's result column collations
+ * flag: -1 if no flag column needed, 0 or 1 to create a const flag column
+ * varno: varno to use in generated Vars
+ * hack_constants: true to copy up constants (see comments in code)
+ * input_tlist: targetlist of this node's input node
+ * refnames_tlist: targetlist to take column names from
+ */
+static List *
+generate_setop_tlist(List *colTypes, List *colCollations,
+					 int flag,
+					 Index varno,
+					 bool hack_constants,
+					 List *input_tlist,
+					 List *refnames_tlist)
+{
+	List	   *tlist = NIL;
+	int			resno = 1;
+	ListCell   *ctlc,
+			   *cclc,
+			   *itlc,
+			   *rtlc;
+	TargetEntry *tle;
+	Node	   *expr;
+
+	forfour(ctlc, colTypes, cclc, colCollations,
+			itlc, input_tlist, rtlc, refnames_tlist)
+	{
+		Oid			colType = lfirst_oid(ctlc);
+		Oid			colColl = lfirst_oid(cclc);
+		TargetEntry *inputtle = (TargetEntry *) lfirst(itlc);
+		TargetEntry *reftle = (TargetEntry *) lfirst(rtlc);
+
+		Assert(inputtle->resno == resno);
+		Assert(reftle->resno == resno);
+		Assert(!inputtle->resjunk);
+		Assert(!reftle->resjunk);
+
+		/*
+		 * Generate columns referencing input columns and having appropriate
+		 * data types and column names.  Insert datatype coercions where
+		 * necessary.
+		 *
+		 * HACK: constants in the input's targetlist are copied up as-is
+		 * rather than being referenced as subquery outputs.  This is mainly
+		 * to ensure that when we try to coerce them to the output column's
+		 * datatype, the right things happen for UNKNOWN constants.  But do
+		 * this only at the first level of subquery-scan plans; we don't want
+		 * phony constants appearing in the output tlists of upper-level
+		 * nodes!
+		 */
+		if (hack_constants && inputtle->expr && IsA(inputtle->expr, Const))
+			expr = (Node *) inputtle->expr;
+		else
+			expr = (Node *) makeVar(varno,
+									inputtle->resno,
+									exprType((Node *) inputtle->expr),
+									exprTypmod((Node *) inputtle->expr),
+									exprCollation((Node *) inputtle->expr),
+									0);
+
+		if (exprType(expr) != colType)
+		{
+			/*
+			 * Note: it's not really cool to be applying coerce_to_common_type
+			 * here; one notable point is that assign_expr_collations never
+			 * gets run on any generated nodes.  For the moment that's not a
+			 * problem because we force the correct exposed collation below.
+			 * It would likely be best to make the parser generate the correct
+			 * output tlist for every set-op to begin with, though.
+			 */
+			expr = coerce_to_common_type(NULL,	/* no UNKNOWNs here */
+										 expr,
+										 colType,
+										 "UNION/INTERSECT/EXCEPT");
+		}
+
+		/*
+		 * Ensure the tlist entry's exposed collation matches the set-op. This
+		 * is necessary because plan_set_operations() reports the result
+		 * ordering as a list of SortGroupClauses, which don't carry collation
+		 * themselves but just refer to tlist entries.  If we don't show the
+		 * right collation then planner.c might do the wrong thing in
+		 * higher-level queries.
+		 *
+		 * Note we use RelabelType, not CollateExpr, since this expression
+		 * will reach the executor without any further processing.
+		 */
+		if (exprCollation(expr) != colColl)
+			expr = applyRelabelType(expr,
+									exprType(expr), exprTypmod(expr), colColl,
+									COERCE_IMPLICIT_CAST, -1, false);
+
+		tle = makeTargetEntry((Expr *) expr,
+							  (AttrNumber) resno++,
+							  pstrdup(reftle->resname),
+							  false);
+
+		/*
+		 * By convention, all non-resjunk columns in a setop tree have
+		 * ressortgroupref equal to their resno.  In some cases the ref isn't
+		 * needed, but this is a cleaner way than modifying the tlist later.
+		 */
+		tle->ressortgroupref = tle->resno;
+
+		tlist = lappend(tlist, tle);
+	}
+
+	if (flag >= 0)
+	{
+		/* Add a resjunk flag column */
+		/* flag value is the given constant */
+		expr = (Node *) makeConst(INT4OID,
+								  -1,
+								  InvalidOid,
+								  sizeof(int32),
+								  Int32GetDatum(flag),
+								  false,
+								  true);
+		tle = makeTargetEntry((Expr *) expr,
+							  (AttrNumber) resno++,
+							  pstrdup("flag"),
+							  true);
+		tlist = lappend(tlist, tle);
+	}
+
+	return tlist;
+}
+
+/*
+ * Generate targetlist for a set-operation Append node
+ *
+ * colTypes: OID list of set-op's result column datatypes
+ * colCollations: OID list of set-op's result column collations
+ * flag: true to create a flag column copied up from subplans
+ * input_tlists: list of tlists for sub-plans of the Append
+ * refnames_tlist: targetlist to take column names from
+ *
+ * The entries in the Append's targetlist should always be simple Vars;
+ * we just have to make sure they have the right datatypes/typmods/collations.
+ * The Vars are always generated with varno 0.
+ *
+ * XXX a problem with the varno-zero approach is that set_pathtarget_cost_width
+ * cannot figure out a realistic width for the tlist we make here.  But we
+ * ought to refactor this code to produce a PathTarget directly, anyway.
+ */
+static List *
+generate_append_tlist(List *colTypes, List *colCollations,
+					  bool flag,
+					  List *input_tlists,
+					  List *refnames_tlist)
+{
+	List	   *tlist = NIL;
+	int			resno = 1;
+	ListCell   *curColType;
+	ListCell   *curColCollation;
+	ListCell   *ref_tl_item;
+	int			colindex;
+	TargetEntry *tle;
+	Node	   *expr;
+	ListCell   *tlistl;
+	int32	   *colTypmods;
+
+	/*
+	 * First extract typmods to use.
+	 *
+	 * If the inputs all agree on type and typmod of a particular column, use
+	 * that typmod; else use -1.
+	 */
+	colTypmods = (int32 *) palloc(list_length(colTypes) * sizeof(int32));
+
+	foreach(tlistl, input_tlists)
+	{
+		List	   *subtlist = (List *) lfirst(tlistl);
+		ListCell   *subtlistl;
+
+		curColType = list_head(colTypes);
+		colindex = 0;
+		foreach(subtlistl, subtlist)
+		{
+			TargetEntry *subtle = (TargetEntry *) lfirst(subtlistl);
+
+			if (subtle->resjunk)
+				continue;
+			Assert(curColType != NULL);
+			if (exprType((Node *) subtle->expr) == lfirst_oid(curColType))
+			{
+				/* If first subplan, copy the typmod; else compare */
+				int32		subtypmod = exprTypmod((Node *) subtle->expr);
+
+				if (tlistl == list_head(input_tlists))
+					colTypmods[colindex] = subtypmod;
+				else if (subtypmod != colTypmods[colindex])
+					colTypmods[colindex] = -1;
+			}
+			else
+			{
+				/* types disagree, so force typmod to -1 */
+				colTypmods[colindex] = -1;
+			}
+			curColType = lnext(colTypes, curColType);
+			colindex++;
+		}
+		Assert(curColType == NULL);
+	}
+
+	/*
+	 * Now we can build the tlist for the Append.
+	 */
+	colindex = 0;
+	forthree(curColType, colTypes, curColCollation, colCollations,
+			 ref_tl_item, refnames_tlist)
+	{
+		Oid			colType = lfirst_oid(curColType);
+		int32		colTypmod = colTypmods[colindex++];
+		Oid			colColl = lfirst_oid(curColCollation);
+		TargetEntry *reftle = (TargetEntry *) lfirst(ref_tl_item);
+
+		Assert(reftle->resno == resno);
+		Assert(!reftle->resjunk);
+		expr = (Node *) makeVar(0,
+								resno,
+								colType,
+								colTypmod,
+								colColl,
+								0);
+		tle = makeTargetEntry((Expr *) expr,
+							  (AttrNumber) resno++,
+							  pstrdup(reftle->resname),
+							  false);
+
+		/*
+		 * By convention, all non-resjunk columns in a setop tree have
+		 * ressortgroupref equal to their resno.  In some cases the ref isn't
+		 * needed, but this is a cleaner way than modifying the tlist later.
+		 */
+		tle->ressortgroupref = tle->resno;
+
+		tlist = lappend(tlist, tle);
+	}
+
+	if (flag)
+	{
+		/* Add a resjunk flag column */
+		/* flag value is shown as copied up from subplan */
+		expr = (Node *) makeVar(0,
+								resno,
+								INT4OID,
+								-1,
+								InvalidOid,
+								0);
+		tle = makeTargetEntry((Expr *) expr,
+							  (AttrNumber) resno++,
+							  pstrdup("flag"),
+							  true);
+		tlist = lappend(tlist, tle);
+	}
+
+	pfree(colTypmods);
+
+	return tlist;
+}
+
+/*
+ * generate_setop_grouplist
+ *		Build a SortGroupClause list defining the sort/grouping properties
+ *		of the setop's output columns.
+ *
+ * Parse analysis already determined the properties and built a suitable
+ * list, except that the entries do not have sortgrouprefs set because
+ * the parser output representation doesn't include a tlist for each
+ * setop.  So what we need to do here is copy that list and install
+ * proper sortgrouprefs into it (copying those from the targetlist).
+ */
+static List *
+generate_setop_grouplist(SetOperationStmt *op, List *targetlist)
+{
+	List	   *grouplist = copyObject(op->groupClauses);
+	ListCell   *lg;
+	ListCell   *lt;
+
+	lg = list_head(grouplist);
+	foreach(lt, targetlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(lt);
+		SortGroupClause *sgc;
+
+		if (tle->resjunk)
+		{
+			/* resjunk columns should not have sortgrouprefs */
+			Assert(tle->ressortgroupref == 0);
+			continue;			/* ignore resjunk columns */
+		}
+
+		/* non-resjunk columns should have sortgroupref = resno */
+		Assert(tle->ressortgroupref == tle->resno);
+
+		/* non-resjunk columns should have grouping clauses */
+		Assert(lg != NULL);
+		sgc = (SortGroupClause *) lfirst(lg);
+		lg = lnext(grouplist, lg);
+		Assert(sgc->tleSortGroupRef == 0);
+
+		sgc->tleSortGroupRef = tle->ressortgroupref;
+	}
+	Assert(lg == NULL);
+	return grouplist;
+}