Adding upstream version 14.5.upstream/14.5upstream

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

1 files changed, 1420 insertions, 0 deletions

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;
+}