aboutsummaryrefslogtreecommitdiff
path: root/src/backend/optimizer/path/costsize.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/backend/optimizer/path/costsize.c')
-rw-r--r--src/backend/optimizer/path/costsize.c375
1 files changed, 10 insertions, 365 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 4c9d8d9cbd5..b39c928eba1 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -126,7 +126,6 @@ bool enable_nestloop = true;
bool enable_material = true;
bool enable_mergejoin = true;
bool enable_hashjoin = true;
-bool enable_fkey_estimates = true;
typedef struct
{
@@ -3889,361 +3888,6 @@ get_parameterized_joinrel_size(PlannerInfo *root, RelOptInfo *rel,
}
/*
- * quals_match_foreign_key
- * Determines if the foreign key is matched by joinquals.
- *
- * Checks that there are conditions on all columns of the foreign key, matching
- * the operator used by the foreign key etc. If such complete match is found,
- * the function returns bitmap identifying the matching quals (0-based).
- *
- * Otherwise (no match at all or incomplete match), NULL is returned.
- *
- * XXX It seems possible in the future to do something useful when a
- * partial match occurs between join and FK, but that is less common
- * and that part isn't worked out yet.
- */
-static Bitmapset *
-quals_match_foreign_key(PlannerInfo *root, ForeignKeyOptInfo *fkinfo,
- RelOptInfo *fkrel, RelOptInfo *foreignrel,
- List *joinquals)
-{
- int i;
- int nkeys = fkinfo->nkeys;
- Bitmapset *qualmatches = NULL;
- Bitmapset *fkmatches = NULL;
-
- /*
- * Loop over each column of the foreign key and build a bitmapset
- * of each joinqual which matches. Note that we don't stop when we find
- * the first match, as the expression could be duplicated in the
- * joinquals, and we want to generate a bitmapset which has bits set for
- * every matching join qual.
- */
- for (i = 0; i < nkeys; i++)
- {
- ListCell *lc;
- int quallstidx = -1;
-
- foreach(lc, joinquals)
- {
- RestrictInfo *rinfo;
- OpExpr *clause;
- Var *leftvar;
- Var *rightvar;
-
- quallstidx++;
-
- /*
- * Technically we don't need to, but here we skip this qual if
- * we've matched it to part of the foreign key already. This
- * should prove to be a useful optimization when the quals appear
- * in the same order as the foreign key's keys. We need only bother
- * doing this when the foreign key is made up of more than 1 set
- * of columns, and we're not testing the first column.
- */
- if (i > 0 && bms_is_member(quallstidx, qualmatches))
- continue;
-
- rinfo = (RestrictInfo *) lfirst(lc);
- clause = (OpExpr *) rinfo->clause;
-
- /* only OpExprs are useful for consideration */
- if (!IsA(clause, OpExpr))
- continue;
-
- /*
- * If the operator does not match then there's little point in
- * checking the operands.
- */
- if (clause->opno != fkinfo->conpfeqop[i])
- continue;
-
- leftvar = (Var *) get_leftop((Expr *) clause);
- rightvar = (Var *) get_rightop((Expr *) clause);
-
- /* Foreign keys only support Vars, so ignore anything more complex */
- if (!IsA(leftvar, Var) || !IsA(rightvar, Var))
- continue;
-
- /*
- * For RestrictInfos built from an eclass we must consider each
- * member of the eclass as rinfo's operands may not belong to the
- * foreign key. For efficient tracking of which Vars we've found,
- * since we're only tracking 2 Vars, we use a bitmask. We can
- * safely finish searching when both of the least significant bits
- * are set.
- */
- if (rinfo->parent_ec)
- {
- EquivalenceClass *ec = rinfo->parent_ec;
- ListCell *lc2;
- int foundvarmask = 0;
-
- foreach(lc2, ec->ec_members)
- {
- EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
- Var *var = (Var *) em->em_expr;
-
- if (!IsA(var, Var))
- continue;
-
- if (foreignrel->relid == var->varno &&
- fkinfo->confkeys[i] == var->varattno)
- foundvarmask |= 1;
-
- else if (fkrel->relid == var->varno &&
- fkinfo->conkeys[i] == var->varattno)
- foundvarmask |= 2;
-
- /*
- * Check if we've found both matches. If found we add
- * this qual to the matched list and mark this key as
- * matched too.
- */
- if (foundvarmask == 3)
- {
- qualmatches = bms_add_member(qualmatches, quallstidx);
- fkmatches = bms_add_member(fkmatches, i);
- break;
- }
- }
- }
- else
- {
- /*
- * In this non eclass RestrictInfo case we'll check if the left
- * and right Vars match to this part of the foreign key.
- * Remember that this could be written with the Vars in either
- * order, so we test both permutations of the expression.
- */
- if ((foreignrel->relid == leftvar->varno) &&
- (fkrel->relid == rightvar->varno) &&
- (fkinfo->confkeys[i] == leftvar->varattno) &&
- (fkinfo->conkeys[i] == rightvar->varattno))
- {
- qualmatches = bms_add_member(qualmatches, quallstidx);
- fkmatches = bms_add_member(fkmatches, i);
- }
- else if ((foreignrel->relid == rightvar->varno) &&
- (fkrel->relid == leftvar->varno) &&
- (fkinfo->confkeys[i] == rightvar->varattno) &&
- (fkinfo->conkeys[i] == leftvar->varattno))
- {
- qualmatches = bms_add_member(qualmatches, quallstidx);
- fkmatches = bms_add_member(fkmatches, i);
- }
- }
- }
- }
-
- /* can't find more matches than columns in the foreign key */
- Assert(bms_num_members(fkmatches) <= nkeys);
-
- /* Only return the matches if the foreign key is matched fully. */
- if (bms_num_members(fkmatches) == nkeys)
- {
- bms_free(fkmatches);
- return qualmatches;
- }
-
- bms_free(fkmatches);
- bms_free(qualmatches);
-
- return NULL;
-}
-
-/*
- * find_best_foreign_key_quals
- * Finds the foreign key best matching the joinquals.
- *
- * Analyzes joinquals to determine if any quals match foreign keys defined the
- * two relations (fkrel referencing foreignrel). When multiple foreign keys
- * match, we choose the one with the most keys as the best one because of the
- * way estimation occurs in clauselist_join_selectivity(). We could choose
- * the FK matching the most quals, however we assume the quals may be duplicated.
- *
- * We also track which joinquals match the current foreign key, so that we can
- * easily skip then when computing the selectivity.
- *
- * When no matching foreign key is found we return 0, otherwise we return the
- * number of keys in the foreign key.
- *
- * Foreign keys matched only partially are currently ignored.
- */
-static int
-find_best_foreign_key_quals(PlannerInfo *root, RelOptInfo *fkrel,
- RelOptInfo *foreignrel, List *joinquals,
- Bitmapset **joinqualsbitmap)
-{
- Bitmapset *qualbestmatch;
- ListCell *lc;
- int bestmatchnkeys;
-
- /*
- * fast path out when there's no foreign keys on fkrel, or when use of
- * foreign keys for estimation is disabled by GUC
- */
- if ((fkrel->fkeylist == NIL) || (!enable_fkey_estimates))
- {
- *joinqualsbitmap = NULL;
- return 0;
- }
-
- qualbestmatch = NULL;
- bestmatchnkeys = 0;
-
- /* now check the matches for each foreign key defined on the fkrel */
- foreach(lc, fkrel->fkeylist)
- {
- ForeignKeyOptInfo *fkinfo = (ForeignKeyOptInfo *) lfirst(lc);
- Bitmapset *qualsmatched;
-
- /*
- * We make no attempt in checking that this foreign key actually
- * references 'foreignrel', the reasoning here is that we may be able
- * to match the foreign key to an eclass member Var of a RestrictInfo
- * that's in qualslist, this Var may belong to some other relation.
- *
- * XXX Is this assumption safe in all cases? Maybe not, but does
- * it lead to a worse estimate than the previous approach? Doubt it.
- */
- qualsmatched = quals_match_foreign_key(root, fkinfo, fkrel, foreignrel,
- joinquals);
-
- /* Did we get a match? And is that match better than a previous one? */
- if (qualsmatched != NULL && fkinfo->nkeys > bestmatchnkeys)
- {
- /* save the new best match */
- bms_free(qualbestmatch);
- qualbestmatch = qualsmatched;
- bestmatchnkeys = fkinfo->nkeys;
- }
- }
-
- *joinqualsbitmap = qualbestmatch;
- return bestmatchnkeys;
-}
-
-/*
- * clauselist_join_selectivity
- * Estimate selectivity of join clauses either by using foreign key info
- * or by using the regular clauselist_selectivity().
- *
- * Since selectivity estimates for each joinqual are multiplied together, this
- * can cause significant underestimates on the number of join tuples in cases
- * where there's more than 1 clause in the join condition. To help ease the
- * pain here we make use of foreign keys, and we assume that 1 row will match
- * when *all* of the foreign key columns are present in the join condition, any
- * additional clauses are estimated using clauselist_selectivity().
- *
- * Note this ignores whether the FK is invalid or currently deferred; we don't
- * rely on this assumption for correctness of the query, so it is a reasonable
- * and safe assumption for planning purposes.
- */
-static Selectivity
-clauselist_join_selectivity(PlannerInfo *root, List *joinquals,
- JoinType jointype, SpecialJoinInfo *sjinfo)
-{
- int outerid;
- int innerid;
- Selectivity sel = 1.0;
- Bitmapset *foundfkquals = NULL;
-
- innerid = -1;
- while ((innerid = bms_next_member(sjinfo->min_righthand, innerid)) >= 0)
- {
- RelOptInfo *innerrel = find_base_rel(root, innerid);
-
- outerid = -1;
- while ((outerid = bms_next_member(sjinfo->min_lefthand, outerid)) >= 0)
- {
- RelOptInfo *outerrel = find_base_rel(root, outerid);
- Bitmapset *outer2inner;
- Bitmapset *inner2outer;
- int innermatches;
- int outermatches;
-
- /*
- * check which quals are matched by a foreign key referencing the
- * innerrel.
- */
- outermatches = find_best_foreign_key_quals(root, outerrel,
- innerrel, joinquals, &outer2inner);
-
- /* do the same, but with relations swapped */
- innermatches = find_best_foreign_key_quals(root, innerrel,
- outerrel, joinquals, &inner2outer);
-
- /*
- * did we find any matches at all? If so we need to see which one is
- * the best/longest match
- */
- if (outermatches != 0 || innermatches != 0)
- {
- double referenced_tuples;
- bool overlap;
-
- /* either could be zero, but not both. */
- if (outermatches < innermatches)
- {
- overlap = bms_overlap(foundfkquals, inner2outer);
-
- foundfkquals = bms_add_members(foundfkquals, inner2outer);
- referenced_tuples = Max(outerrel->tuples, 1.0);
- }
- else
- {
- overlap = bms_overlap(foundfkquals, outer2inner);
-
- foundfkquals = bms_add_members(foundfkquals, outer2inner);
- referenced_tuples = Max(innerrel->tuples, 1.0);
- }
-
- /*
- * XXX should we ignore these overlapping matches?
- * Or perhaps take the Max() or Min()?
- */
- if (overlap)
- {
- if (jointype == JOIN_SEMI || jointype == JOIN_ANTI)
- sel = Min(sel,Min(1.0 / (outerrel->tuples / Max(innerrel->tuples, 1.0)), 1.0));
- else
- sel = Min(sel, 1.0 / referenced_tuples);
- }
- else
- {
- if (jointype == JOIN_SEMI || jointype == JOIN_ANTI)
- sel *= Min(1.0 / (outerrel->tuples / Max(innerrel->tuples, 1.0)), 1.0);
- else
- sel *= 1.0 / referenced_tuples;
- }
- }
- }
- }
-
- /*
- * If any non matched quals exist then we build a list of the non-matches
- * and use clauselist_selectivity() to estimate the selectivity of these.
- */
- if (bms_num_members(foundfkquals) < list_length(joinquals))
- {
- ListCell *lc;
- int lstidx = 0;
- List *nonfkeyclauses = NIL;
-
- foreach (lc, joinquals)
- {
- if (!bms_is_member(lstidx, foundfkquals))
- nonfkeyclauses = lappend(nonfkeyclauses, lfirst(lc));
- lstidx++;
- }
- sel *= clauselist_selectivity(root, nonfkeyclauses, 0, jointype, sjinfo);
- }
-
- return sel;
-}
-
-/*
* calc_joinrel_size_estimate
* Workhorse for set_joinrel_size_estimates and
* get_parameterized_joinrel_size.
@@ -4289,11 +3933,11 @@ calc_joinrel_size_estimate(PlannerInfo *root,
}
/* Get the separate selectivities */
- jselec = clauselist_join_selectivity(root,
- joinquals,
- jointype,
- sjinfo);
-
+ jselec = clauselist_selectivity(root,
+ joinquals,
+ 0,
+ jointype,
+ sjinfo);
pselec = clauselist_selectivity(root,
pushedquals,
0,
@@ -4306,10 +3950,11 @@ calc_joinrel_size_estimate(PlannerInfo *root,
}
else
{
- jselec = clauselist_join_selectivity(root,
- restrictlist,
- jointype,
- sjinfo);
+ jselec = clauselist_selectivity(root,
+ restrictlist,
+ 0,
+ jointype,
+ sjinfo);
pselec = 0.0; /* not used, keep compiler quiet */
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-17 14:29:58 +0000