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+/*-------------------------------------------------------------------------
+ *
+ * clausesel.c
+ * Routines to compute clause selectivities
+ *
+ * Portions Copyright (c) 1996-2021, 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-26 11:20:07 +0000