/*------------------------------------------------------------------------- * * restrictinfo.c * RestrictInfo node manipulation routines. * * Portions Copyright (c) 1996-2015, 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 "optimizer/clauses.h" #include "optimizer/restrictinfo.h" #include "optimizer/var.h" static RestrictInfo *make_restrictinfo_internal(Expr *clause, Expr *orclause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids, Relids outer_relids, Relids nullable_relids); static Expr *make_sub_restrictinfos(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, 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 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(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, 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 (or_clause((Node *) clause)) return (RestrictInfo *) make_sub_restrictinfos(clause, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, outer_relids, nullable_relids); /* Shouldn't be an AND clause, else AND/OR flattening messed up */ Assert(!and_clause((Node *) clause)); return make_restrictinfo_internal(clause, NULL, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, outer_relids, nullable_relids); } /* * make_restrictinfos_from_actual_clauses * * Given a list of implicitly-ANDed restriction clauses, produce a list * of RestrictInfo nodes. This is used to reconstitute the RestrictInfo * representation after doing transformations of a list of clauses. * * We assume that the clauses are relation-level restrictions and therefore * we don't have to worry about is_pushed_down, outerjoin_delayed, * outer_relids, and nullable_relids (these can be assumed true, false, * NULL, and NULL, respectively). * We do take care to recognize pseudoconstant clauses properly. */ List * make_restrictinfos_from_actual_clauses(PlannerInfo *root, List *clause_list) { List *result = NIL; ListCell *l; foreach(l, clause_list) { Expr *clause = (Expr *) lfirst(l); bool pseudoconstant; RestrictInfo *rinfo; /* * It's pseudoconstant if it contains no Vars and no volatile * functions. We probably can't see any sublinks here, so * contain_var_clause() would likely be enough, but for safety use * contain_vars_of_level() instead. */ pseudoconstant = !contain_vars_of_level((Node *) clause, 0) && !contain_volatile_functions((Node *) clause); if (pseudoconstant) { /* tell createplan.c to check for gating quals */ root->hasPseudoConstantQuals = true; } rinfo = make_restrictinfo(clause, true, false, pseudoconstant, NULL, NULL, NULL); result = lappend(result, rinfo); } return result; } /* * make_restrictinfo_internal * * Common code for the main entry points and the recursive cases. */ static RestrictInfo * make_restrictinfo_internal(Expr *clause, Expr *orclause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, 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->outer_relids = outer_relids; restrictinfo->nullable_relids = nullable_relids; /* * 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(get_leftop(clause)); restrictinfo->right_relids = pull_varnos(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((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; 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 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(Expr *clause, bool is_pushed_down, bool outerjoin_delayed, bool pseudoconstant, Relids required_relids, Relids outer_relids, Relids nullable_relids) { if (or_clause((Node *) clause)) { List *orlist = NIL; ListCell *temp; foreach(temp, ((BoolExpr *) clause)->args) orlist = lappend(orlist, make_sub_restrictinfos(lfirst(temp), is_pushed_down, outerjoin_delayed, pseudoconstant, NULL, outer_relids, nullable_relids)); return (Expr *) make_restrictinfo_internal(clause, make_orclause(orlist), is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, outer_relids, nullable_relids); } else if (and_clause((Node *) clause)) { List *andlist = NIL; ListCell *temp; foreach(temp, ((BoolExpr *) clause)->args) andlist = lappend(andlist, make_sub_restrictinfos(lfirst(temp), is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, outer_relids, nullable_relids)); return make_andclause(andlist); } else return (Expr *) make_restrictinfo_internal(clause, NULL, is_pushed_down, outerjoin_delayed, pseudoconstant, required_relids, outer_relids, nullable_relids); } /* * 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; } /* * 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 = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); Assert(!rinfo->pseudoconstant); result = lappend(result, rinfo->clause); } return result; } /* * get_all_actual_clauses * * Returns a list containing the bare clauses from 'restrictinfo_list'. * * This loses the distinction between regular and pseudoconstant clauses, * so be careful what you use it for. */ List * get_all_actual_clauses(List *restrictinfo_list) { List *result = NIL; ListCell *l; foreach(l, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); 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 = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); if (rinfo->pseudoconstant == pseudoconstant) result = lappend(result, rinfo->clause); } return result; } /* * extract_actual_join_clauses * * Extract bare clauses from 'restrictinfo_list', separating those that * syntactically 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, List **joinquals, List **otherquals) { ListCell *l; *joinquals = NIL; *otherquals = NIL; foreach(l, restrictinfo_list) { RestrictInfo *rinfo = (RestrictInfo *) lfirst(l); Assert(IsA(rinfo, RestrictInfo)); if (rinfo->is_pushed_down) { 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; }