diff options
Diffstat (limited to '')
| -rw-r--r-- | src/backend/optimizer/util/restrictinfo.c | 624 |
1 files changed, 624 insertions, 0 deletions
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c new file mode 100644 index 0000000..aa9fb3a --- /dev/null +++ b/src/backend/optimizer/util/restrictinfo.c @@ -0,0 +1,624 @@ +/*------------------------------------------------------------------------- + * + * restrictinfo.c + * RestrictInfo node manipulation routines. + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/optimizer/util/restrictinfo.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "nodes/makefuncs.h" +#include "nodes/nodeFuncs.h" +#include "optimizer/clauses.h" +#include "optimizer/optimizer.h" +#include "optimizer/restrictinfo.h" + + +static RestrictInfo *make_restrictinfo_internal(PlannerInfo *root, + Expr *clause, + Expr *orclause, + bool is_pushed_down, + bool outerjoin_delayed, + bool pseudoconstant, + Index security_level, + Relids required_relids, + Relids outer_relids, + Relids nullable_relids); +static Expr *make_sub_restrictinfos(PlannerInfo *root, + Expr *clause, + bool is_pushed_down, + bool outerjoin_delayed, + bool pseudoconstant, + Index security_level, + Relids required_relids, + Relids outer_relids, + Relids nullable_relids); + + +/* + * make_restrictinfo + * + * Build a RestrictInfo node containing the given subexpression. + * + * The is_pushed_down, outerjoin_delayed, and pseudoconstant flags for the + * RestrictInfo must be supplied by the caller, as well as the correct values + * for security_level, outer_relids, and nullable_relids. + * required_relids can be NULL, in which case it defaults to the actual clause + * contents (i.e., clause_relids). + * + * We initialize fields that depend only on the given subexpression, leaving + * others that depend on context (or may never be needed at all) to be filled + * later. + */ +RestrictInfo * +make_restrictinfo(PlannerInfo *root, + Expr *clause, + bool is_pushed_down, + bool outerjoin_delayed, + bool pseudoconstant, + Index security_level, + Relids required_relids, + Relids outer_relids, + Relids nullable_relids) +{ + /* + * If it's an OR clause, build a modified copy with RestrictInfos inserted + * above each subclause of the top-level AND/OR structure. + */ + if (is_orclause(clause)) + return (RestrictInfo *) make_sub_restrictinfos(root, + clause, + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + required_relids, + outer_relids, + nullable_relids); + + /* Shouldn't be an AND clause, else AND/OR flattening messed up */ + Assert(!is_andclause(clause)); + + return make_restrictinfo_internal(root, + clause, + NULL, + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + required_relids, + outer_relids, + nullable_relids); +} + +/* + * make_restrictinfo_internal + * + * Common code for the main entry points and the recursive cases. + */ +static RestrictInfo * +make_restrictinfo_internal(PlannerInfo *root, + Expr *clause, + Expr *orclause, + bool is_pushed_down, + bool outerjoin_delayed, + bool pseudoconstant, + Index security_level, + Relids required_relids, + Relids outer_relids, + Relids nullable_relids) +{ + RestrictInfo *restrictinfo = makeNode(RestrictInfo); + + restrictinfo->clause = clause; + restrictinfo->orclause = orclause; + restrictinfo->is_pushed_down = is_pushed_down; + restrictinfo->outerjoin_delayed = outerjoin_delayed; + restrictinfo->pseudoconstant = pseudoconstant; + restrictinfo->can_join = false; /* may get set below */ + restrictinfo->security_level = security_level; + restrictinfo->outer_relids = outer_relids; + restrictinfo->nullable_relids = nullable_relids; + + /* + * If it's potentially delayable by lower-level security quals, figure out + * whether it's leakproof. We can skip testing this for level-zero quals, + * since they would never get delayed on security grounds anyway. + */ + if (security_level > 0) + restrictinfo->leakproof = !contain_leaked_vars((Node *) clause); + else + restrictinfo->leakproof = false; /* really, "don't know" */ + + /* + * Mark volatility as unknown. The contain_volatile_functions function + * will determine if there are any volatile functions when called for the + * first time with this RestrictInfo. + */ + restrictinfo->has_volatile = VOLATILITY_UNKNOWN; + + /* + * If it's a binary opclause, set up left/right relids info. In any case + * set up the total clause relids info. + */ + if (is_opclause(clause) && list_length(((OpExpr *) clause)->args) == 2) + { + restrictinfo->left_relids = pull_varnos(root, get_leftop(clause)); + restrictinfo->right_relids = pull_varnos(root, get_rightop(clause)); + + restrictinfo->clause_relids = bms_union(restrictinfo->left_relids, + restrictinfo->right_relids); + + /* + * Does it look like a normal join clause, i.e., a binary operator + * relating expressions that come from distinct relations? If so we + * might be able to use it in a join algorithm. Note that this is a + * purely syntactic test that is made regardless of context. + */ + if (!bms_is_empty(restrictinfo->left_relids) && + !bms_is_empty(restrictinfo->right_relids) && + !bms_overlap(restrictinfo->left_relids, + restrictinfo->right_relids)) + { + restrictinfo->can_join = true; + /* pseudoconstant should certainly not be true */ + Assert(!restrictinfo->pseudoconstant); + } + } + else + { + /* Not a binary opclause, so mark left/right relid sets as empty */ + restrictinfo->left_relids = NULL; + restrictinfo->right_relids = NULL; + /* and get the total relid set the hard way */ + restrictinfo->clause_relids = pull_varnos(root, (Node *) clause); + } + + /* required_relids defaults to clause_relids */ + if (required_relids != NULL) + restrictinfo->required_relids = required_relids; + else + restrictinfo->required_relids = restrictinfo->clause_relids; + + /* + * Fill in all the cacheable fields with "not yet set" markers. None of + * these will be computed until/unless needed. Note in particular that we + * don't mark a binary opclause as mergejoinable or hashjoinable here; + * that happens only if it appears in the right context (top level of a + * joinclause list). + */ + restrictinfo->parent_ec = NULL; + + restrictinfo->eval_cost.startup = -1; + restrictinfo->norm_selec = -1; + restrictinfo->outer_selec = -1; + + restrictinfo->mergeopfamilies = NIL; + + restrictinfo->left_ec = NULL; + restrictinfo->right_ec = NULL; + restrictinfo->left_em = NULL; + restrictinfo->right_em = NULL; + restrictinfo->scansel_cache = NIL; + + restrictinfo->outer_is_left = false; + + restrictinfo->hashjoinoperator = InvalidOid; + + restrictinfo->left_bucketsize = -1; + restrictinfo->right_bucketsize = -1; + restrictinfo->left_mcvfreq = -1; + restrictinfo->right_mcvfreq = -1; + + restrictinfo->hasheqoperator = InvalidOid; + + return restrictinfo; +} + +/* + * Recursively insert sub-RestrictInfo nodes into a boolean expression. + * + * We put RestrictInfos above simple (non-AND/OR) clauses and above + * sub-OR clauses, but not above sub-AND clauses, because there's no need. + * This may seem odd but it is closely related to the fact that we use + * implicit-AND lists at top level of RestrictInfo lists. Only ORs and + * simple clauses are valid RestrictInfos. + * + * The same is_pushed_down, outerjoin_delayed, and pseudoconstant flag + * values can be applied to all RestrictInfo nodes in the result. Likewise + * for security_level, outer_relids, and nullable_relids. + * + * The given required_relids are attached to our top-level output, + * but any OR-clause constituents are allowed to default to just the + * contained rels. + */ +static Expr * +make_sub_restrictinfos(PlannerInfo *root, + Expr *clause, + bool is_pushed_down, + bool outerjoin_delayed, + bool pseudoconstant, + Index security_level, + Relids required_relids, + Relids outer_relids, + Relids nullable_relids) +{ + if (is_orclause(clause)) + { + List *orlist = NIL; + ListCell *temp; + + foreach(temp, ((BoolExpr *) clause)->args) + orlist = lappend(orlist, + make_sub_restrictinfos(root, + lfirst(temp), + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + NULL, + outer_relids, + nullable_relids)); + return (Expr *) make_restrictinfo_internal(root, + clause, + make_orclause(orlist), + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + required_relids, + outer_relids, + nullable_relids); + } + else if (is_andclause(clause)) + { + List *andlist = NIL; + ListCell *temp; + + foreach(temp, ((BoolExpr *) clause)->args) + andlist = lappend(andlist, + make_sub_restrictinfos(root, + lfirst(temp), + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + required_relids, + outer_relids, + nullable_relids)); + return make_andclause(andlist); + } + else + return (Expr *) make_restrictinfo_internal(root, + clause, + NULL, + is_pushed_down, + outerjoin_delayed, + pseudoconstant, + security_level, + required_relids, + outer_relids, + nullable_relids); +} + +/* + * commute_restrictinfo + * + * Given a RestrictInfo containing a binary opclause, produce a RestrictInfo + * representing the commutation of that clause. The caller must pass the + * OID of the commutator operator (which it's presumably looked up, else + * it would not know this is valid). + * + * Beware that the result shares sub-structure with the given RestrictInfo. + * That's okay for the intended usage with derived index quals, but might + * be hazardous if the source is subject to change. Also notice that we + * assume without checking that the commutator op is a member of the same + * btree and hash opclasses as the original op. + */ +RestrictInfo * +commute_restrictinfo(RestrictInfo *rinfo, Oid comm_op) +{ + RestrictInfo *result; + OpExpr *newclause; + OpExpr *clause = castNode(OpExpr, rinfo->clause); + + Assert(list_length(clause->args) == 2); + + /* flat-copy all the fields of clause ... */ + newclause = makeNode(OpExpr); + memcpy(newclause, clause, sizeof(OpExpr)); + + /* ... and adjust those we need to change to commute it */ + newclause->opno = comm_op; + newclause->opfuncid = InvalidOid; + newclause->args = list_make2(lsecond(clause->args), + linitial(clause->args)); + + /* likewise, flat-copy all the fields of rinfo ... */ + result = makeNode(RestrictInfo); + memcpy(result, rinfo, sizeof(RestrictInfo)); + + /* + * ... and adjust those we need to change. Note in particular that we can + * preserve any cached selectivity or cost estimates, since those ought to + * be the same for the new clause. Likewise we can keep the source's + * parent_ec. + */ + result->clause = (Expr *) newclause; + result->left_relids = rinfo->right_relids; + result->right_relids = rinfo->left_relids; + Assert(result->orclause == NULL); + result->left_ec = rinfo->right_ec; + result->right_ec = rinfo->left_ec; + result->left_em = rinfo->right_em; + result->right_em = rinfo->left_em; + result->scansel_cache = NIL; /* not worth updating this */ + if (rinfo->hashjoinoperator == clause->opno) + result->hashjoinoperator = comm_op; + else + result->hashjoinoperator = InvalidOid; + result->left_bucketsize = rinfo->right_bucketsize; + result->right_bucketsize = rinfo->left_bucketsize; + result->left_mcvfreq = rinfo->right_mcvfreq; + result->right_mcvfreq = rinfo->left_mcvfreq; + result->hasheqoperator = InvalidOid; + + return result; +} + +/* + * restriction_is_or_clause + * + * Returns t iff the restrictinfo node contains an 'or' clause. + */ +bool +restriction_is_or_clause(RestrictInfo *restrictinfo) +{ + if (restrictinfo->orclause != NULL) + return true; + else + return false; +} + +/* + * restriction_is_securely_promotable + * + * Returns true if it's okay to evaluate this clause "early", that is before + * other restriction clauses attached to the specified relation. + */ +bool +restriction_is_securely_promotable(RestrictInfo *restrictinfo, + RelOptInfo *rel) +{ + /* + * It's okay if there are no baserestrictinfo clauses for the rel that + * would need to go before this one, *or* if this one is leakproof. + */ + if (restrictinfo->security_level <= rel->baserestrict_min_security || + restrictinfo->leakproof) + return true; + else + return false; +} + +/* + * get_actual_clauses + * + * Returns a list containing the bare clauses from 'restrictinfo_list'. + * + * This is only to be used in cases where none of the RestrictInfos can + * be pseudoconstant clauses (for instance, it's OK on indexqual lists). + */ +List * +get_actual_clauses(List *restrictinfo_list) +{ + List *result = NIL; + ListCell *l; + + foreach(l, restrictinfo_list) + { + RestrictInfo *rinfo = lfirst_node(RestrictInfo, l); + + Assert(!rinfo->pseudoconstant); + + result = lappend(result, rinfo->clause); + } + return result; +} + +/* + * extract_actual_clauses + * + * Extract bare clauses from 'restrictinfo_list', returning either the + * regular ones or the pseudoconstant ones per 'pseudoconstant'. + */ +List * +extract_actual_clauses(List *restrictinfo_list, + bool pseudoconstant) +{ + List *result = NIL; + ListCell *l; + + foreach(l, restrictinfo_list) + { + RestrictInfo *rinfo = lfirst_node(RestrictInfo, l); + + if (rinfo->pseudoconstant == pseudoconstant) + result = lappend(result, rinfo->clause); + } + return result; +} + +/* + * extract_actual_join_clauses + * + * Extract bare clauses from 'restrictinfo_list', separating those that + * semantically match the join level from those that were pushed down. + * Pseudoconstant clauses are excluded from the results. + * + * This is only used at outer joins, since for plain joins we don't care + * about pushed-down-ness. + */ +void +extract_actual_join_clauses(List *restrictinfo_list, + Relids joinrelids, + List **joinquals, + List **otherquals) +{ + ListCell *l; + + *joinquals = NIL; + *otherquals = NIL; + + foreach(l, restrictinfo_list) + { + RestrictInfo *rinfo = lfirst_node(RestrictInfo, l); + + if (RINFO_IS_PUSHED_DOWN(rinfo, joinrelids)) + { + if (!rinfo->pseudoconstant) + *otherquals = lappend(*otherquals, rinfo->clause); + } + else + { + /* joinquals shouldn't have been marked pseudoconstant */ + Assert(!rinfo->pseudoconstant); + *joinquals = lappend(*joinquals, rinfo->clause); + } + } +} + + +/* + * join_clause_is_movable_to + * Test whether a join clause is a safe candidate for parameterization + * of a scan on the specified base relation. + * + * A movable join clause is one that can safely be evaluated at a rel below + * its normal semantic level (ie, its required_relids), if the values of + * variables that it would need from other rels are provided. + * + * We insist that the clause actually reference the target relation; this + * prevents undesirable movement of degenerate join clauses, and ensures + * that there is a unique place that a clause can be moved down to. + * + * We cannot move an outer-join clause into the non-nullable side of its + * outer join, as that would change the results (rows would be suppressed + * rather than being null-extended). + * + * Also there must not be an outer join below the clause that would null the + * Vars coming from the target relation. Otherwise the clause might give + * results different from what it would give at its normal semantic level. + * + * Also, the join clause must not use any relations that have LATERAL + * references to the target relation, since we could not put such rels on + * the outer side of a nestloop with the target relation. + */ +bool +join_clause_is_movable_to(RestrictInfo *rinfo, RelOptInfo *baserel) +{ + /* Clause must physically reference target rel */ + if (!bms_is_member(baserel->relid, rinfo->clause_relids)) + return false; + + /* Cannot move an outer-join clause into the join's outer side */ + if (bms_is_member(baserel->relid, rinfo->outer_relids)) + return false; + + /* Target rel must not be nullable below the clause */ + if (bms_is_member(baserel->relid, rinfo->nullable_relids)) + return false; + + /* Clause must not use any rels with LATERAL references to this rel */ + if (bms_overlap(baserel->lateral_referencers, rinfo->clause_relids)) + return false; + + return true; +} + +/* + * join_clause_is_movable_into + * Test whether a join clause is movable and can be evaluated within + * the current join context. + * + * currentrelids: the relids of the proposed evaluation location + * current_and_outer: the union of currentrelids and the required_outer + * relids (parameterization's outer relations) + * + * The API would be a bit clearer if we passed the current relids and the + * outer relids separately and did bms_union internally; but since most + * callers need to apply this function to multiple clauses, we make the + * caller perform the union. + * + * Obviously, the clause must only refer to Vars available from the current + * relation plus the outer rels. We also check that it does reference at + * least one current Var, ensuring that the clause will be pushed down to + * a unique place in a parameterized join tree. And we check that we're + * not pushing the clause into its outer-join outer side, nor down into + * a lower outer join's inner side. + * + * The check about pushing a clause down into a lower outer join's inner side + * is only approximate; it sometimes returns "false" when actually it would + * be safe to use the clause here because we're still above the outer join + * in question. This is okay as long as the answers at different join levels + * are consistent: it just means we might sometimes fail to push a clause as + * far down as it could safely be pushed. It's unclear whether it would be + * worthwhile to do this more precisely. (But if it's ever fixed to be + * exactly accurate, there's an Assert in get_joinrel_parampathinfo() that + * should be re-enabled.) + * + * There's no check here equivalent to join_clause_is_movable_to's test on + * lateral_referencers. We assume the caller wouldn't be inquiring unless + * it'd verified that the proposed outer rels don't have lateral references + * to the current rel(s). (If we are considering join paths with the outer + * rels on the outside and the current rels on the inside, then this should + * have been checked at the outset of such consideration; see join_is_legal + * and the path parameterization checks in joinpath.c.) On the other hand, + * in join_clause_is_movable_to we are asking whether the clause could be + * moved for some valid set of outer rels, so we don't have the benefit of + * relying on prior checks for lateral-reference validity. + * + * Note: if this returns true, it means that the clause could be moved to + * this join relation, but that doesn't mean that this is the lowest join + * it could be moved to. Caller may need to make additional calls to verify + * that this doesn't succeed on either of the inputs of a proposed join. + * + * Note: get_joinrel_parampathinfo depends on the fact that if + * current_and_outer is NULL, this function will always return false + * (since one or the other of the first two tests must fail). + */ +bool +join_clause_is_movable_into(RestrictInfo *rinfo, + Relids currentrelids, + Relids current_and_outer) +{ + /* Clause must be evaluable given available context */ + if (!bms_is_subset(rinfo->clause_relids, current_and_outer)) + return false; + + /* Clause must physically reference at least one target rel */ + if (!bms_overlap(currentrelids, rinfo->clause_relids)) + return false; + + /* Cannot move an outer-join clause into the join's outer side */ + if (bms_overlap(currentrelids, rinfo->outer_relids)) + return false; + + /* + * Target rel(s) must not be nullable below the clause. This is + * approximate, in the safe direction, because the current join might be + * above the join where the nulling would happen, in which case the clause + * would work correctly here. But we don't have enough info to be sure. + */ + if (bms_overlap(currentrelids, rinfo->nullable_relids)) + return false; + + return true; +} |