Adding upstream version 15.5.upstream/15.5

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

1 files changed, 1000 insertions, 0 deletions

diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
new file mode 100644
index 0000000..06f8363
--- /dev/null
+++ b/src/backend/optimizer/path/clausesel.c
@@ -0,0 +1,1000 @@
+/*-------------------------------------------------------------------------
+ *
+ * clausesel.c
+ *	  Routines to compute clause selectivities
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/optimizer/path/clausesel.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "nodes/makefuncs.h"
+#include "nodes/nodeFuncs.h"
+#include "optimizer/clauses.h"
+#include "optimizer/cost.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/pathnode.h"
+#include "optimizer/plancat.h"
+#include "statistics/statistics.h"
+#include "utils/fmgroids.h"
+#include "utils/lsyscache.h"
+#include "utils/selfuncs.h"
+
+/*
+ * Data structure for accumulating info about possible range-query
+ * clause pairs in clauselist_selectivity.
+ */
+typedef struct RangeQueryClause
+{
+	struct RangeQueryClause *next;	/* next in linked list */
+	Node	   *var;			/* The common variable of the clauses */
+	bool		have_lobound;	/* found a low-bound clause yet? */
+	bool		have_hibound;	/* found a high-bound clause yet? */
+	Selectivity lobound;		/* Selectivity of a var > something clause */
+	Selectivity hibound;		/* Selectivity of a var < something clause */
+} RangeQueryClause;
+
+static void addRangeClause(RangeQueryClause **rqlist, Node *clause,
+						   bool varonleft, bool isLTsel, Selectivity s2);
+static RelOptInfo *find_single_rel_for_clauses(PlannerInfo *root,
+											   List *clauses);
+static Selectivity clauselist_selectivity_or(PlannerInfo *root,
+											 List *clauses,
+											 int varRelid,
+											 JoinType jointype,
+											 SpecialJoinInfo *sjinfo,
+											 bool use_extended_stats);
+
+/****************************************************************************
+ *		ROUTINES TO COMPUTE SELECTIVITIES
+ ****************************************************************************/
+
+/*
+ * clauselist_selectivity -
+ *	  Compute the selectivity of an implicitly-ANDed list of boolean
+ *	  expression clauses.  The list can be empty, in which case 1.0
+ *	  must be returned.  List elements may be either RestrictInfos
+ *	  or bare expression clauses --- the former is preferred since
+ *	  it allows caching of results.
+ *
+ * See clause_selectivity() for the meaning of the additional parameters.
+ *
+ * The basic approach is to apply extended statistics first, on as many
+ * clauses as possible, in order to capture cross-column dependencies etc.
+ * The remaining clauses are then estimated by taking the product of their
+ * selectivities, but that's only right if they have independent
+ * probabilities, and in reality they are often NOT independent even if they
+ * only refer to a single column.  So, we want to be smarter where we can.
+ *
+ * We also recognize "range queries", such as "x > 34 AND x < 42".  Clauses
+ * are recognized as possible range query components if they are restriction
+ * opclauses whose operators have scalarltsel or a related function as their
+ * restriction selectivity estimator.  We pair up clauses of this form that
+ * refer to the same variable.  An unpairable clause of this kind is simply
+ * multiplied into the selectivity product in the normal way.  But when we
+ * find a pair, we know that the selectivities represent the relative
+ * positions of the low and high bounds within the column's range, so instead
+ * of figuring the selectivity as hisel * losel, we can figure it as hisel +
+ * losel - 1.  (To visualize this, see that hisel is the fraction of the range
+ * below the high bound, while losel is the fraction above the low bound; so
+ * hisel can be interpreted directly as a 0..1 value but we need to convert
+ * losel to 1-losel before interpreting it as a value.  Then the available
+ * range is 1-losel to hisel.  However, this calculation double-excludes
+ * nulls, so really we need hisel + losel + null_frac - 1.)
+ *
+ * If either selectivity is exactly DEFAULT_INEQ_SEL, we forget this equation
+ * and instead use DEFAULT_RANGE_INEQ_SEL.  The same applies if the equation
+ * yields an impossible (negative) result.
+ *
+ * A free side-effect is that we can recognize redundant inequalities such
+ * as "x < 4 AND x < 5"; only the tighter constraint will be counted.
+ *
+ * Of course this is all very dependent on the behavior of the inequality
+ * selectivity functions; perhaps some day we can generalize the approach.
+ */
+Selectivity
+clauselist_selectivity(PlannerInfo *root,
+					   List *clauses,
+					   int varRelid,
+					   JoinType jointype,
+					   SpecialJoinInfo *sjinfo)
+{
+	return clauselist_selectivity_ext(root, clauses, varRelid,
+									  jointype, sjinfo, true);
+}
+
+/*
+ * clauselist_selectivity_ext -
+ *	  Extended version of clauselist_selectivity().  If "use_extended_stats"
+ *	  is false, all extended statistics will be ignored, and only per-column
+ *	  statistics will be used.
+ */
+Selectivity
+clauselist_selectivity_ext(PlannerInfo *root,
+						   List *clauses,
+						   int varRelid,
+						   JoinType jointype,
+						   SpecialJoinInfo *sjinfo,
+						   bool use_extended_stats)
+{
+	Selectivity s1 = 1.0;
+	RelOptInfo *rel;
+	Bitmapset  *estimatedclauses = NULL;
+	RangeQueryClause *rqlist = NULL;
+	ListCell   *l;
+	int			listidx;
+
+	/*
+	 * If there's exactly one clause, just go directly to
+	 * clause_selectivity_ext(). None of what we might do below is relevant.
+	 */
+	if (list_length(clauses) == 1)
+		return clause_selectivity_ext(root, (Node *) linitial(clauses),
+									  varRelid, jointype, sjinfo,
+									  use_extended_stats);
+
+	/*
+	 * Determine if these clauses reference a single relation.  If so, and if
+	 * it has extended statistics, try to apply those.
+	 */
+	rel = find_single_rel_for_clauses(root, clauses);
+	if (use_extended_stats && rel && rel->rtekind == RTE_RELATION && rel->statlist != NIL)
+	{
+		/*
+		 * Estimate as many clauses as possible using extended statistics.
+		 *
+		 * 'estimatedclauses' is populated with the 0-based list position
+		 * index of clauses estimated here, and that should be ignored below.
+		 */
+		s1 = statext_clauselist_selectivity(root, clauses, varRelid,
+											jointype, sjinfo, rel,
+											&estimatedclauses, false);
+	}
+
+	/*
+	 * Apply normal selectivity estimates for remaining clauses. We'll be
+	 * careful to skip any clauses which were already estimated above.
+	 *
+	 * Anything that doesn't look like a potential rangequery clause gets
+	 * multiplied into s1 and forgotten. Anything that does gets inserted into
+	 * an rqlist entry.
+	 */
+	listidx = -1;
+	foreach(l, clauses)
+	{
+		Node	   *clause = (Node *) lfirst(l);
+		RestrictInfo *rinfo;
+		Selectivity s2;
+
+		listidx++;
+
+		/*
+		 * Skip this clause if it's already been estimated by some other
+		 * statistics above.
+		 */
+		if (bms_is_member(listidx, estimatedclauses))
+			continue;
+
+		/* Compute the selectivity of this clause in isolation */
+		s2 = clause_selectivity_ext(root, clause, varRelid, jointype, sjinfo,
+									use_extended_stats);
+
+		/*
+		 * Check for being passed a RestrictInfo.
+		 *
+		 * If it's a pseudoconstant RestrictInfo, then s2 is either 1.0 or
+		 * 0.0; just use that rather than looking for range pairs.
+		 */
+		if (IsA(clause, RestrictInfo))
+		{
+			rinfo = (RestrictInfo *) clause;
+			if (rinfo->pseudoconstant)
+			{
+				s1 = s1 * s2;
+				continue;
+			}
+			clause = (Node *) rinfo->clause;
+		}
+		else
+			rinfo = NULL;
+
+		/*
+		 * See if it looks like a restriction clause with a pseudoconstant on
+		 * one side.  (Anything more complicated than that might not behave in
+		 * the simple way we are expecting.)  Most of the tests here can be
+		 * done more efficiently with rinfo than without.
+		 */
+		if (is_opclause(clause) && list_length(((OpExpr *) clause)->args) == 2)
+		{
+			OpExpr	   *expr = (OpExpr *) clause;
+			bool		varonleft = true;
+			bool		ok;
+
+			if (rinfo)
+			{
+				ok = (bms_membership(rinfo->clause_relids) == BMS_SINGLETON) &&
+					(is_pseudo_constant_clause_relids(lsecond(expr->args),
+													  rinfo->right_relids) ||
+					 (varonleft = false,
+					  is_pseudo_constant_clause_relids(linitial(expr->args),
+													   rinfo->left_relids)));
+			}
+			else
+			{
+				ok = (NumRelids(root, clause) == 1) &&
+					(is_pseudo_constant_clause(lsecond(expr->args)) ||
+					 (varonleft = false,
+					  is_pseudo_constant_clause(linitial(expr->args))));
+			}
+
+			if (ok)
+			{
+				/*
+				 * If it's not a "<"/"<="/">"/">=" operator, just merge the
+				 * selectivity in generically.  But if it's the right oprrest,
+				 * add the clause to rqlist for later processing.
+				 */
+				switch (get_oprrest(expr->opno))
+				{
+					case F_SCALARLTSEL:
+					case F_SCALARLESEL:
+						addRangeClause(&rqlist, clause,
+									   varonleft, true, s2);
+						break;
+					case F_SCALARGTSEL:
+					case F_SCALARGESEL:
+						addRangeClause(&rqlist, clause,
+									   varonleft, false, s2);
+						break;
+					default:
+						/* Just merge the selectivity in generically */
+						s1 = s1 * s2;
+						break;
+				}
+				continue;		/* drop to loop bottom */
+			}
+		}
+
+		/* Not the right form, so treat it generically. */
+		s1 = s1 * s2;
+	}
+
+	/*
+	 * Now scan the rangequery pair list.
+	 */
+	while (rqlist != NULL)
+	{
+		RangeQueryClause *rqnext;
+
+		if (rqlist->have_lobound && rqlist->have_hibound)
+		{
+			/* Successfully matched a pair of range clauses */
+			Selectivity s2;
+
+			/*
+			 * Exact equality to the default value probably means the
+			 * selectivity function punted.  This is not airtight but should
+			 * be good enough.
+			 */
+			if (rqlist->hibound == DEFAULT_INEQ_SEL ||
+				rqlist->lobound == DEFAULT_INEQ_SEL)
+			{
+				s2 = DEFAULT_RANGE_INEQ_SEL;
+			}
+			else
+			{
+				s2 = rqlist->hibound + rqlist->lobound - 1.0;
+
+				/* Adjust for double-exclusion of NULLs */
+				s2 += nulltestsel(root, IS_NULL, rqlist->var,
+								  varRelid, jointype, sjinfo);
+
+				/*
+				 * A zero or slightly negative s2 should be converted into a
+				 * small positive value; we probably are dealing with a very
+				 * tight range and got a bogus result due to roundoff errors.
+				 * However, if s2 is very negative, then we probably have
+				 * default selectivity estimates on one or both sides of the
+				 * range that we failed to recognize above for some reason.
+				 */
+				if (s2 <= 0.0)
+				{
+					if (s2 < -0.01)
+					{
+						/*
+						 * No data available --- use a default estimate that
+						 * is small, but not real small.
+						 */
+						s2 = DEFAULT_RANGE_INEQ_SEL;
+					}
+					else
+					{
+						/*
+						 * It's just roundoff error; use a small positive
+						 * value
+						 */
+						s2 = 1.0e-10;
+					}
+				}
+			}
+			/* Merge in the selectivity of the pair of clauses */
+			s1 *= s2;
+		}
+		else
+		{
+			/* Only found one of a pair, merge it in generically */
+			if (rqlist->have_lobound)
+				s1 *= rqlist->lobound;
+			else
+				s1 *= rqlist->hibound;
+		}
+		/* release storage and advance */
+		rqnext = rqlist->next;
+		pfree(rqlist);
+		rqlist = rqnext;
+	}
+
+	return s1;
+}
+
+/*
+ * clauselist_selectivity_or -
+ *	  Compute the selectivity of an implicitly-ORed list of boolean
+ *	  expression clauses.  The list can be empty, in which case 0.0
+ *	  must be returned.  List elements may be either RestrictInfos
+ *	  or bare expression clauses --- the former is preferred since
+ *	  it allows caching of results.
+ *
+ * See clause_selectivity() for the meaning of the additional parameters.
+ *
+ * The basic approach is to apply extended statistics first, on as many
+ * clauses as possible, in order to capture cross-column dependencies etc.
+ * The remaining clauses are then estimated as if they were independent.
+ */
+static Selectivity
+clauselist_selectivity_or(PlannerInfo *root,
+						  List *clauses,
+						  int varRelid,
+						  JoinType jointype,
+						  SpecialJoinInfo *sjinfo,
+						  bool use_extended_stats)
+{
+	Selectivity s1 = 0.0;
+	RelOptInfo *rel;
+	Bitmapset  *estimatedclauses = NULL;
+	ListCell   *lc;
+	int			listidx;
+
+	/*
+	 * Determine if these clauses reference a single relation.  If so, and if
+	 * it has extended statistics, try to apply those.
+	 */
+	rel = find_single_rel_for_clauses(root, clauses);
+	if (use_extended_stats && rel && rel->rtekind == RTE_RELATION && rel->statlist != NIL)
+	{
+		/*
+		 * Estimate as many clauses as possible using extended statistics.
+		 *
+		 * 'estimatedclauses' is populated with the 0-based list position
+		 * index of clauses estimated here, and that should be ignored below.
+		 */
+		s1 = statext_clauselist_selectivity(root, clauses, varRelid,
+											jointype, sjinfo, rel,
+											&estimatedclauses, true);
+	}
+
+	/*
+	 * Estimate the remaining clauses as if they were independent.
+	 *
+	 * Selectivities for an OR clause are computed as s1+s2 - s1*s2 to account
+	 * for the probable overlap of selected tuple sets.
+	 *
+	 * XXX is this too conservative?
+	 */
+	listidx = -1;
+	foreach(lc, clauses)
+	{
+		Selectivity s2;
+
+		listidx++;
+
+		/*
+		 * Skip this clause if it's already been estimated by some other
+		 * statistics above.
+		 */
+		if (bms_is_member(listidx, estimatedclauses))
+			continue;
+
+		s2 = clause_selectivity_ext(root, (Node *) lfirst(lc), varRelid,
+									jointype, sjinfo, use_extended_stats);
+
+		s1 = s1 + s2 - s1 * s2;
+	}
+
+	return s1;
+}
+
+/*
+ * addRangeClause --- add a new range clause for clauselist_selectivity
+ *
+ * Here is where we try to match up pairs of range-query clauses
+ */
+static void
+addRangeClause(RangeQueryClause **rqlist, Node *clause,
+			   bool varonleft, bool isLTsel, Selectivity s2)
+{
+	RangeQueryClause *rqelem;
+	Node	   *var;
+	bool		is_lobound;
+
+	if (varonleft)
+	{
+		var = get_leftop((Expr *) clause);
+		is_lobound = !isLTsel;	/* x < something is high bound */
+	}
+	else
+	{
+		var = get_rightop((Expr *) clause);
+		is_lobound = isLTsel;	/* something < x is low bound */
+	}
+
+	for (rqelem = *rqlist; rqelem; rqelem = rqelem->next)
+	{
+		/*
+		 * We use full equal() here because the "var" might be a function of
+		 * one or more attributes of the same relation...
+		 */
+		if (!equal(var, rqelem->var))
+			continue;
+		/* Found the right group to put this clause in */
+		if (is_lobound)
+		{
+			if (!rqelem->have_lobound)
+			{
+				rqelem->have_lobound = true;
+				rqelem->lobound = s2;
+			}
+			else
+			{
+
+				/*------
+				 * We have found two similar clauses, such as
+				 * x < y AND x <= z.
+				 * Keep only the more restrictive one.
+				 *------
+				 */
+				if (rqelem->lobound > s2)
+					rqelem->lobound = s2;
+			}
+		}
+		else
+		{
+			if (!rqelem->have_hibound)
+			{
+				rqelem->have_hibound = true;
+				rqelem->hibound = s2;
+			}
+			else
+			{
+
+				/*------
+				 * We have found two similar clauses, such as
+				 * x > y AND x >= z.
+				 * Keep only the more restrictive one.
+				 *------
+				 */
+				if (rqelem->hibound > s2)
+					rqelem->hibound = s2;
+			}
+		}
+		return;
+	}
+
+	/* No matching var found, so make a new clause-pair data structure */
+	rqelem = (RangeQueryClause *) palloc(sizeof(RangeQueryClause));
+	rqelem->var = var;
+	if (is_lobound)
+	{
+		rqelem->have_lobound = true;
+		rqelem->have_hibound = false;
+		rqelem->lobound = s2;
+	}
+	else
+	{
+		rqelem->have_lobound = false;
+		rqelem->have_hibound = true;
+		rqelem->hibound = s2;
+	}
+	rqelem->next = *rqlist;
+	*rqlist = rqelem;
+}
+
+/*
+ * find_single_rel_for_clauses
+ *		Examine each clause in 'clauses' and determine if all clauses
+ *		reference only a single relation.  If so return that relation,
+ *		otherwise return NULL.
+ */
+static RelOptInfo *
+find_single_rel_for_clauses(PlannerInfo *root, List *clauses)
+{
+	int			lastrelid = 0;
+	ListCell   *l;
+
+	foreach(l, clauses)
+	{
+		RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
+		int			relid;
+
+		/*
+		 * If we have a list of bare clauses rather than RestrictInfos, we
+		 * could pull out their relids the hard way with pull_varnos().
+		 * However, currently the extended-stats machinery won't do anything
+		 * with non-RestrictInfo clauses anyway, so there's no point in
+		 * spending extra cycles; just fail if that's what we have.
+		 *
+		 * An exception to that rule is if we have a bare BoolExpr AND clause.
+		 * We treat this as a special case because the restrictinfo machinery
+		 * doesn't build RestrictInfos on top of AND clauses.
+		 */
+		if (is_andclause(rinfo))
+		{
+			RelOptInfo *rel;
+
+			rel = find_single_rel_for_clauses(root,
+											  ((BoolExpr *) rinfo)->args);
+
+			if (rel == NULL)
+				return NULL;
+			if (lastrelid == 0)
+				lastrelid = rel->relid;
+			else if (rel->relid != lastrelid)
+				return NULL;
+
+			continue;
+		}
+
+		if (!IsA(rinfo, RestrictInfo))
+			return NULL;
+
+		if (bms_is_empty(rinfo->clause_relids))
+			continue;			/* we can ignore variable-free clauses */
+		if (!bms_get_singleton_member(rinfo->clause_relids, &relid))
+			return NULL;		/* multiple relations in this clause */
+		if (lastrelid == 0)
+			lastrelid = relid;	/* first clause referencing a relation */
+		else if (relid != lastrelid)
+			return NULL;		/* relation not same as last one */
+	}
+
+	if (lastrelid != 0)
+		return find_base_rel(root, lastrelid);
+
+	return NULL;				/* no clauses */
+}
+
+/*
+ * bms_is_subset_singleton
+ *
+ * Same result as bms_is_subset(s, bms_make_singleton(x)),
+ * but a little faster and doesn't leak memory.
+ *
+ * Is this of use anywhere else?  If so move to bitmapset.c ...
+ */
+static bool
+bms_is_subset_singleton(const Bitmapset *s, int x)
+{
+	switch (bms_membership(s))
+	{
+		case BMS_EMPTY_SET:
+			return true;
+		case BMS_SINGLETON:
+			return bms_is_member(x, s);
+		case BMS_MULTIPLE:
+			return false;
+	}
+	/* can't get here... */
+	return false;
+}
+
+/*
+ * treat_as_join_clause -
+ *	  Decide whether an operator clause is to be handled by the
+ *	  restriction or join estimator.  Subroutine for clause_selectivity().
+ */
+static inline bool
+treat_as_join_clause(PlannerInfo *root, Node *clause, RestrictInfo *rinfo,
+					 int varRelid, SpecialJoinInfo *sjinfo)
+{
+	if (varRelid != 0)
+	{
+		/*
+		 * Caller is forcing restriction mode (eg, because we are examining an
+		 * inner indexscan qual).
+		 */
+		return false;
+	}
+	else if (sjinfo == NULL)
+	{
+		/*
+		 * It must be a restriction clause, since it's being evaluated at a
+		 * scan node.
+		 */
+		return false;
+	}
+	else
+	{
+		/*
+		 * Otherwise, it's a join if there's more than one relation used. We
+		 * can optimize this calculation if an rinfo was passed.
+		 *
+		 * XXX	Since we know the clause is being evaluated at a join, the
+		 * only way it could be single-relation is if it was delayed by outer
+		 * joins.  Although we can make use of the restriction qual estimators
+		 * anyway, it seems likely that we ought to account for the
+		 * probability of injected nulls somehow.
+		 */
+		if (rinfo)
+			return (bms_membership(rinfo->clause_relids) == BMS_MULTIPLE);
+		else
+			return (NumRelids(root, clause) > 1);
+	}
+}
+
+
+/*
+ * clause_selectivity -
+ *	  Compute the selectivity of a general boolean expression clause.
+ *
+ * The clause can be either a RestrictInfo or a plain expression.  If it's
+ * a RestrictInfo, we try to cache the selectivity for possible re-use,
+ * so passing RestrictInfos is preferred.
+ *
+ * varRelid is either 0 or a rangetable index.
+ *
+ * When varRelid is not 0, only variables belonging to that relation are
+ * considered in computing selectivity; other vars are treated as constants
+ * of unknown values.  This is appropriate for estimating the selectivity of
+ * a join clause that is being used as a restriction clause in a scan of a
+ * nestloop join's inner relation --- varRelid should then be the ID of the
+ * inner relation.
+ *
+ * When varRelid is 0, all variables are treated as variables.  This
+ * is appropriate for ordinary join clauses and restriction clauses.
+ *
+ * jointype is the join type, if the clause is a join clause.  Pass JOIN_INNER
+ * if the clause isn't a join clause.
+ *
+ * sjinfo is NULL for a non-join clause, otherwise it provides additional
+ * context information about the join being performed.  There are some
+ * special cases:
+ *	1. For a special (not INNER) join, sjinfo is always a member of
+ *	   root->join_info_list.
+ *	2. For an INNER join, sjinfo is just a transient struct, and only the
+ *	   relids and jointype fields in it can be trusted.
+ * It is possible for jointype to be different from sjinfo->jointype.
+ * This indicates we are considering a variant join: either with
+ * the LHS and RHS switched, or with one input unique-ified.
+ *
+ * Note: when passing nonzero varRelid, it's normally appropriate to set
+ * jointype == JOIN_INNER, sjinfo == NULL, even if the clause is really a
+ * join clause; because we aren't treating it as a join clause.
+ */
+Selectivity
+clause_selectivity(PlannerInfo *root,
+				   Node *clause,
+				   int varRelid,
+				   JoinType jointype,
+				   SpecialJoinInfo *sjinfo)
+{
+	return clause_selectivity_ext(root, clause, varRelid,
+								  jointype, sjinfo, true);
+}
+
+/*
+ * clause_selectivity_ext -
+ *	  Extended version of clause_selectivity().  If "use_extended_stats" is
+ *	  false, all extended statistics will be ignored, and only per-column
+ *	  statistics will be used.
+ */
+Selectivity
+clause_selectivity_ext(PlannerInfo *root,
+					   Node *clause,
+					   int varRelid,
+					   JoinType jointype,
+					   SpecialJoinInfo *sjinfo,
+					   bool use_extended_stats)
+{
+	Selectivity s1 = 0.5;		/* default for any unhandled clause type */
+	RestrictInfo *rinfo = NULL;
+	bool		cacheable = false;
+
+	if (clause == NULL)			/* can this still happen? */
+		return s1;
+
+	if (IsA(clause, RestrictInfo))
+	{
+		rinfo = (RestrictInfo *) clause;
+
+		/*
+		 * If the clause is marked pseudoconstant, then it will be used as a
+		 * gating qual and should not affect selectivity estimates; hence
+		 * return 1.0.  The only exception is that a constant FALSE may be
+		 * taken as having selectivity 0.0, since it will surely mean no rows
+		 * out of the plan.  This case is simple enough that we need not
+		 * bother caching the result.
+		 */
+		if (rinfo->pseudoconstant)
+		{
+			if (!IsA(rinfo->clause, Const))
+				return (Selectivity) 1.0;
+		}
+
+		/*
+		 * If the clause is marked redundant, always return 1.0.
+		 */
+		if (rinfo->norm_selec > 1)
+			return (Selectivity) 1.0;
+
+		/*
+		 * If possible, cache the result of the selectivity calculation for
+		 * the clause.  We can cache if varRelid is zero or the clause
+		 * contains only vars of that relid --- otherwise varRelid will affect
+		 * the result, so mustn't cache.  Outer join quals might be examined
+		 * with either their join's actual jointype or JOIN_INNER, so we need
+		 * two cache variables to remember both cases.  Note: we assume the
+		 * result won't change if we are switching the input relations or
+		 * considering a unique-ified case, so we only need one cache variable
+		 * for all non-JOIN_INNER cases.
+		 */
+		if (varRelid == 0 ||
+			bms_is_subset_singleton(rinfo->clause_relids, varRelid))
+		{
+			/* Cacheable --- do we already have the result? */
+			if (jointype == JOIN_INNER)
+			{
+				if (rinfo->norm_selec >= 0)
+					return rinfo->norm_selec;
+			}
+			else
+			{
+				if (rinfo->outer_selec >= 0)
+					return rinfo->outer_selec;
+			}
+			cacheable = true;
+		}
+
+		/*
+		 * Proceed with examination of contained clause.  If the clause is an
+		 * OR-clause, we want to look at the variant with sub-RestrictInfos,
+		 * so that per-subclause selectivities can be cached.
+		 */
+		if (rinfo->orclause)
+			clause = (Node *) rinfo->orclause;
+		else
+			clause = (Node *) rinfo->clause;
+	}
+
+	if (IsA(clause, Var))
+	{
+		Var		   *var = (Var *) clause;
+
+		/*
+		 * We probably shouldn't ever see an uplevel Var here, but if we do,
+		 * return the default selectivity...
+		 */
+		if (var->varlevelsup == 0 &&
+			(varRelid == 0 || varRelid == (int) var->varno))
+		{
+			/* Use the restriction selectivity function for a bool Var */
+			s1 = boolvarsel(root, (Node *) var, varRelid);
+		}
+	}
+	else if (IsA(clause, Const))
+	{
+		/* bool constant is pretty easy... */
+		Const	   *con = (Const *) clause;
+
+		s1 = con->constisnull ? 0.0 :
+			DatumGetBool(con->constvalue) ? 1.0 : 0.0;
+	}
+	else if (IsA(clause, Param))
+	{
+		/* see if we can replace the Param */
+		Node	   *subst = estimate_expression_value(root, clause);
+
+		if (IsA(subst, Const))
+		{
+			/* bool constant is pretty easy... */
+			Const	   *con = (Const *) subst;
+
+			s1 = con->constisnull ? 0.0 :
+				DatumGetBool(con->constvalue) ? 1.0 : 0.0;
+		}
+		else
+		{
+			/* XXX any way to do better than default? */
+		}
+	}
+	else if (is_notclause(clause))
+	{
+		/* inverse of the selectivity of the underlying clause */
+		s1 = 1.0 - clause_selectivity_ext(root,
+										  (Node *) get_notclausearg((Expr *) clause),
+										  varRelid,
+										  jointype,
+										  sjinfo,
+										  use_extended_stats);
+	}
+	else if (is_andclause(clause))
+	{
+		/* share code with clauselist_selectivity() */
+		s1 = clauselist_selectivity_ext(root,
+										((BoolExpr *) clause)->args,
+										varRelid,
+										jointype,
+										sjinfo,
+										use_extended_stats);
+	}
+	else if (is_orclause(clause))
+	{
+		/*
+		 * Almost the same thing as clauselist_selectivity, but with the
+		 * clauses connected by OR.
+		 */
+		s1 = clauselist_selectivity_or(root,
+									   ((BoolExpr *) clause)->args,
+									   varRelid,
+									   jointype,
+									   sjinfo,
+									   use_extended_stats);
+	}
+	else if (is_opclause(clause) || IsA(clause, DistinctExpr))
+	{
+		OpExpr	   *opclause = (OpExpr *) clause;
+		Oid			opno = opclause->opno;
+
+		if (treat_as_join_clause(root, clause, rinfo, varRelid, sjinfo))
+		{
+			/* Estimate selectivity for a join clause. */
+			s1 = join_selectivity(root, opno,
+								  opclause->args,
+								  opclause->inputcollid,
+								  jointype,
+								  sjinfo);
+		}
+		else
+		{
+			/* Estimate selectivity for a restriction clause. */
+			s1 = restriction_selectivity(root, opno,
+										 opclause->args,
+										 opclause->inputcollid,
+										 varRelid);
+		}
+
+		/*
+		 * DistinctExpr has the same representation as OpExpr, but the
+		 * contained operator is "=" not "<>", so we must negate the result.
+		 * This estimation method doesn't give the right behavior for nulls,
+		 * but it's better than doing nothing.
+		 */
+		if (IsA(clause, DistinctExpr))
+			s1 = 1.0 - s1;
+	}
+	else if (is_funcclause(clause))
+	{
+		FuncExpr   *funcclause = (FuncExpr *) clause;
+
+		/* Try to get an estimate from the support function, if any */
+		s1 = function_selectivity(root,
+								  funcclause->funcid,
+								  funcclause->args,
+								  funcclause->inputcollid,
+								  treat_as_join_clause(root, clause, rinfo,
+													   varRelid, sjinfo),
+								  varRelid,
+								  jointype,
+								  sjinfo);
+	}
+	else if (IsA(clause, ScalarArrayOpExpr))
+	{
+		/* Use node specific selectivity calculation function */
+		s1 = scalararraysel(root,
+							(ScalarArrayOpExpr *) clause,
+							treat_as_join_clause(root, clause, rinfo,
+												 varRelid, sjinfo),
+							varRelid,
+							jointype,
+							sjinfo);
+	}
+	else if (IsA(clause, RowCompareExpr))
+	{
+		/* Use node specific selectivity calculation function */
+		s1 = rowcomparesel(root,
+						   (RowCompareExpr *) clause,
+						   varRelid,
+						   jointype,
+						   sjinfo);
+	}
+	else if (IsA(clause, NullTest))
+	{
+		/* Use node specific selectivity calculation function */
+		s1 = nulltestsel(root,
+						 ((NullTest *) clause)->nulltesttype,
+						 (Node *) ((NullTest *) clause)->arg,
+						 varRelid,
+						 jointype,
+						 sjinfo);
+	}
+	else if (IsA(clause, BooleanTest))
+	{
+		/* Use node specific selectivity calculation function */
+		s1 = booltestsel(root,
+						 ((BooleanTest *) clause)->booltesttype,
+						 (Node *) ((BooleanTest *) clause)->arg,
+						 varRelid,
+						 jointype,
+						 sjinfo);
+	}
+	else if (IsA(clause, CurrentOfExpr))
+	{
+		/* CURRENT OF selects at most one row of its table */
+		CurrentOfExpr *cexpr = (CurrentOfExpr *) clause;
+		RelOptInfo *crel = find_base_rel(root, cexpr->cvarno);
+
+		if (crel->tuples > 0)
+			s1 = 1.0 / crel->tuples;
+	}
+	else if (IsA(clause, RelabelType))
+	{
+		/* Not sure this case is needed, but it can't hurt */
+		s1 = clause_selectivity_ext(root,
+									(Node *) ((RelabelType *) clause)->arg,
+									varRelid,
+									jointype,
+									sjinfo,
+									use_extended_stats);
+	}
+	else if (IsA(clause, CoerceToDomain))
+	{
+		/* Not sure this case is needed, but it can't hurt */
+		s1 = clause_selectivity_ext(root,
+									(Node *) ((CoerceToDomain *) clause)->arg,
+									varRelid,
+									jointype,
+									sjinfo,
+									use_extended_stats);
+	}
+	else
+	{
+		/*
+		 * For anything else, see if we can consider it as a boolean variable.
+		 * This only works if it's an immutable expression in Vars of a single
+		 * relation; but there's no point in us checking that here because
+		 * boolvarsel() will do it internally, and return a suitable default
+		 * selectivity if not.
+		 */
+		s1 = boolvarsel(root, clause, varRelid);
+	}
+
+	/* Cache the result if possible */
+	if (cacheable)
+	{
+		if (jointype == JOIN_INNER)
+			rinfo->norm_selec = s1;
+		else
+			rinfo->outer_selec = s1;
+	}
+
+#ifdef SELECTIVITY_DEBUG
+	elog(DEBUG4, "clause_selectivity: s1 %f", s1);
+#endif							/* SELECTIVITY_DEBUG */
+
+	return s1;
+}