/*------------------------------------------------------------------------- * * initsplan.c * Target list, qualification, joininfo initialization routines * * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.123.2.8 2007/10/24 20:54:33 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "catalog/pg_operator.h" #include "catalog/pg_type.h" #include "optimizer/clauses.h" #include "optimizer/cost.h" #include "optimizer/joininfo.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "optimizer/planmain.h" #include "optimizer/prep.h" #include "optimizer/restrictinfo.h" #include "optimizer/var.h" #include "parser/parse_expr.h" #include "parser/parse_oper.h" #include "utils/builtins.h" #include "utils/lsyscache.h" #include "utils/syscache.h" /* These parameters are set by GUC */ int from_collapse_limit; int join_collapse_limit; static void add_vars_to_targetlist(PlannerInfo *root, List *vars, Relids where_needed); static List *deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join, Relids *qualscope, Relids *inner_join_rels); static OuterJoinInfo *make_outerjoininfo(PlannerInfo *root, Relids left_rels, Relids right_rels, Relids inner_join_rels, bool is_full_join, Node *clause); static void distribute_qual_to_rels(PlannerInfo *root, Node *clause, bool is_deduced, bool below_outer_join, Relids qualscope, Relids ojscope, Relids outerjoin_nonnullable); static bool qual_is_redundant(PlannerInfo *root, RestrictInfo *restrictinfo, List *restrictlist); static void check_mergejoinable(RestrictInfo *restrictinfo); static void check_hashjoinable(RestrictInfo *restrictinfo); /***************************************************************************** * * JOIN TREES * *****************************************************************************/ /* * add_base_rels_to_query * * Scan the query's jointree and create baserel RelOptInfos for all * the base relations (ie, table, subquery, and function RTEs) * appearing in the jointree. * * The initial invocation must pass root->parse->jointree as the value of * jtnode. Internally, the function recurses through the jointree. * * At the end of this process, there should be one baserel RelOptInfo for * every non-join RTE that is used in the query. Therefore, this routine * is the only place that should call build_simple_rel with reloptkind * RELOPT_BASEREL. (Note: build_simple_rel recurses internally to build * "other rel" RelOptInfos for the members of any appendrels we find here.) */ void add_base_rels_to_query(PlannerInfo *root, Node *jtnode) { if (jtnode == NULL) return; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; (void) build_simple_rel(root, varno, RELOPT_BASEREL); } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) add_base_rels_to_query(root, lfirst(l)); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; add_base_rels_to_query(root, j->larg); add_base_rels_to_query(root, j->rarg); } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /***************************************************************************** * * TARGET LISTS * *****************************************************************************/ /* * build_base_rel_tlists * Add targetlist entries for each var needed in the query's final tlist * to the appropriate base relations. * * We mark such vars as needed by "relation 0" to ensure that they will * propagate up through all join plan steps. */ void build_base_rel_tlists(PlannerInfo *root, List *final_tlist) { List *tlist_vars = pull_var_clause((Node *) final_tlist, false); if (tlist_vars != NIL) { add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0)); list_free(tlist_vars); } } /* * add_IN_vars_to_tlists * Add targetlist entries for each var needed in InClauseInfo entries * to the appropriate base relations. * * Normally this is a waste of time because scanning of the WHERE clause * will have added them. But it is possible that eval_const_expressions() * simplified away all references to the vars after the InClauseInfos were * made. We need the IN's righthand-side vars to be available at the join * anyway, in case we try to unique-ify the subselect's outputs. (The only * known case that provokes this is "WHERE false AND foo IN (SELECT ...)". * We don't try to be very smart about such cases, just correct.) */ void add_IN_vars_to_tlists(PlannerInfo *root) { ListCell *l; foreach(l, root->in_info_list) { InClauseInfo *ininfo = (InClauseInfo *) lfirst(l); List *in_vars; in_vars = pull_var_clause((Node *) ininfo->sub_targetlist, false); if (in_vars != NIL) { add_vars_to_targetlist(root, in_vars, bms_union(ininfo->lefthand, ininfo->righthand)); list_free(in_vars); } } } /* * add_vars_to_targetlist * For each variable appearing in the list, add it to the owning * relation's targetlist if not already present, and mark the variable * as being needed for the indicated join (or for final output if * where_needed includes "relation 0"). */ static void add_vars_to_targetlist(PlannerInfo *root, List *vars, Relids where_needed) { ListCell *temp; Assert(!bms_is_empty(where_needed)); foreach(temp, vars) { Var *var = (Var *) lfirst(temp); RelOptInfo *rel = find_base_rel(root, var->varno); int attrno = var->varattno; Assert(attrno >= rel->min_attr && attrno <= rel->max_attr); attrno -= rel->min_attr; if (bms_is_empty(rel->attr_needed[attrno])) { /* Variable not yet requested, so add to reltargetlist */ /* XXX is copyObject necessary here? */ rel->reltargetlist = lappend(rel->reltargetlist, copyObject(var)); } rel->attr_needed[attrno] = bms_add_members(rel->attr_needed[attrno], where_needed); } } /***************************************************************************** * * JOIN TREE PROCESSING * *****************************************************************************/ /* * deconstruct_jointree * Recursively scan the query's join tree for WHERE and JOIN/ON qual * clauses, and add these to the appropriate restrictinfo and joininfo * lists belonging to base RelOptInfos. Also, add OuterJoinInfo nodes * to root->oj_info_list for any outer joins appearing in the query tree. * Return a "joinlist" data structure showing the join order decisions * that need to be made by make_one_rel(). * * The "joinlist" result is a list of items that are either RangeTblRef * jointree nodes or sub-joinlists. All the items at the same level of * joinlist must be joined in an order to be determined by make_one_rel() * (note that legal orders may be constrained by OuterJoinInfo nodes). * A sub-joinlist represents a subproblem to be planned separately. Currently * sub-joinlists arise only from FULL OUTER JOIN or when collapsing of * subproblems is stopped by join_collapse_limit or from_collapse_limit. * * NOTE: when dealing with inner joins, it is appropriate to let a qual clause * be evaluated at the lowest level where all the variables it mentions are * available. However, we cannot push a qual down into the nullable side(s) * of an outer join since the qual might eliminate matching rows and cause a * NULL row to be incorrectly emitted by the join. Therefore, we artificially * OR the minimum-relids of such an outer join into the required_relids of * clauses appearing above it. This forces those clauses to be delayed until * application of the outer join (or maybe even higher in the join tree). */ List * deconstruct_jointree(PlannerInfo *root) { Relids qualscope; Relids inner_join_rels; /* Start recursion at top of jointree */ Assert(root->parse->jointree != NULL && IsA(root->parse->jointree, FromExpr)); return deconstruct_recurse(root, (Node *) root->parse->jointree, false, &qualscope, &inner_join_rels); } /* * deconstruct_recurse * One recursion level of deconstruct_jointree processing. * * Inputs: * jtnode is the jointree node to examine * below_outer_join is TRUE if this node is within the nullable side of a * higher-level outer join * Outputs: * *qualscope gets the set of base Relids syntactically included in this * jointree node (do not modify or free this, as it may also be pointed * to by RestrictInfo and OuterJoinInfo nodes) * *inner_join_rels gets the set of base Relids syntactically included in * inner joins appearing at or below this jointree node (do not modify * or free this, either) * Return value is the appropriate joinlist for this jointree node * * In addition, entries will be added to root->oj_info_list for outer joins. */ static List * deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join, Relids *qualscope, Relids *inner_join_rels) { List *joinlist; if (jtnode == NULL) { *qualscope = NULL; *inner_join_rels = NULL; return NIL; } if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; /* No quals to deal with, just return correct result */ *qualscope = bms_make_singleton(varno); /* A single baserel does not create an inner join */ *inner_join_rels = NULL; joinlist = list_make1(jtnode); } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; int remaining; ListCell *l; /* * First, recurse to handle child joins. We collapse subproblems into * a single joinlist whenever the resulting joinlist wouldn't exceed * from_collapse_limit members. Also, always collapse one-element * subproblems, since that won't lengthen the joinlist anyway. */ *qualscope = NULL; *inner_join_rels = NULL; joinlist = NIL; remaining = list_length(f->fromlist); foreach(l, f->fromlist) { Relids sub_qualscope; List *sub_joinlist; int sub_members; sub_joinlist = deconstruct_recurse(root, lfirst(l), below_outer_join, &sub_qualscope, inner_join_rels); *qualscope = bms_add_members(*qualscope, sub_qualscope); sub_members = list_length(sub_joinlist); remaining--; if (sub_members <= 1 || list_length(joinlist) + sub_members + remaining <= from_collapse_limit) joinlist = list_concat(joinlist, sub_joinlist); else joinlist = lappend(joinlist, sub_joinlist); } /* * A FROM with more than one list element is an inner join subsuming * all below it, so we should report inner_join_rels = qualscope. * If there was exactly one element, we should (and already did) report * whatever its inner_join_rels were. If there were no elements * (is that possible?) the initialization before the loop fixed it. */ if (list_length(f->fromlist) > 1) *inner_join_rels = *qualscope; /* * Now process the top-level quals. */ foreach(l, (List *) f->quals) distribute_qual_to_rels(root, (Node *) lfirst(l), false, below_outer_join, *qualscope, NULL, NULL); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; Relids leftids, rightids, left_inners, right_inners, nonnullable_rels, ojscope; List *leftjoinlist, *rightjoinlist; OuterJoinInfo *ojinfo; ListCell *qual; /* * Order of operations here is subtle and critical. First we recurse * to handle sub-JOINs. Their join quals will be placed without * regard for whether this level is an outer join, which is correct. * Then we place our own join quals, which are restricted by lower * outer joins in any case, and are forced to this level if this is an * outer join and they mention the outer side. Finally, if this is an * outer join, we create an oj_info_list entry for the join. This * will prevent quals above us in the join tree that use those rels * from being pushed down below this level. (It's okay for upper * quals to be pushed down to the outer side, however.) */ switch (j->jointype) { case JOIN_INNER: leftjoinlist = deconstruct_recurse(root, j->larg, below_outer_join, &leftids, &left_inners); rightjoinlist = deconstruct_recurse(root, j->rarg, below_outer_join, &rightids, &right_inners); *qualscope = bms_union(leftids, rightids); *inner_join_rels = *qualscope; /* Inner join adds no restrictions for quals */ nonnullable_rels = NULL; break; case JOIN_LEFT: leftjoinlist = deconstruct_recurse(root, j->larg, below_outer_join, &leftids, &left_inners); rightjoinlist = deconstruct_recurse(root, j->rarg, true, &rightids, &right_inners); *qualscope = bms_union(leftids, rightids); *inner_join_rels = bms_union(left_inners, right_inners); nonnullable_rels = leftids; break; case JOIN_FULL: leftjoinlist = deconstruct_recurse(root, j->larg, true, &leftids, &left_inners); rightjoinlist = deconstruct_recurse(root, j->rarg, true, &rightids, &right_inners); *qualscope = bms_union(leftids, rightids); *inner_join_rels = bms_union(left_inners, right_inners); /* each side is both outer and inner */ nonnullable_rels = *qualscope; break; case JOIN_RIGHT: /* notice we switch leftids and rightids */ leftjoinlist = deconstruct_recurse(root, j->larg, true, &rightids, &right_inners); rightjoinlist = deconstruct_recurse(root, j->rarg, below_outer_join, &leftids, &left_inners); *qualscope = bms_union(leftids, rightids); *inner_join_rels = bms_union(left_inners, right_inners); nonnullable_rels = leftids; break; default: elog(ERROR, "unrecognized join type: %d", (int) j->jointype); nonnullable_rels = NULL; /* keep compiler quiet */ leftjoinlist = rightjoinlist = NIL; break; } /* * For an OJ, form the OuterJoinInfo now, because we need the OJ's * semantic scope (ojscope) to pass to distribute_qual_to_rels. But * we mustn't add it to oj_info_list just yet, because we don't want * distribute_qual_to_rels to think it is an outer join below us. */ if (j->jointype != JOIN_INNER) { ojinfo = make_outerjoininfo(root, leftids, rightids, *inner_join_rels, (j->jointype == JOIN_FULL), j->quals); ojscope = bms_union(ojinfo->min_lefthand, ojinfo->min_righthand); } else { ojinfo = NULL; ojscope = NULL; } /* Process the qual clauses */ foreach(qual, (List *) j->quals) distribute_qual_to_rels(root, (Node *) lfirst(qual), false, below_outer_join, *qualscope, ojscope, nonnullable_rels); /* Now we can add the OuterJoinInfo to oj_info_list */ if (ojinfo) root->oj_info_list = lappend(root->oj_info_list, ojinfo); /* * Finally, compute the output joinlist. We fold subproblems together * except at a FULL JOIN or where join_collapse_limit would be * exceeded. */ if (j->jointype == JOIN_FULL) { /* force the join order exactly at this node */ joinlist = list_make1(list_make2(leftjoinlist, rightjoinlist)); } else if (list_length(leftjoinlist) + list_length(rightjoinlist) <= join_collapse_limit) { /* OK to combine subproblems */ joinlist = list_concat(leftjoinlist, rightjoinlist); } else { /* can't combine, but needn't force join order above here */ Node *leftpart, *rightpart; /* avoid creating useless 1-element sublists */ if (list_length(leftjoinlist) == 1) leftpart = (Node *) linitial(leftjoinlist); else leftpart = (Node *) leftjoinlist; if (list_length(rightjoinlist) == 1) rightpart = (Node *) linitial(rightjoinlist); else rightpart = (Node *) rightjoinlist; joinlist = list_make2(leftpart, rightpart); } } else { elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); joinlist = NIL; /* keep compiler quiet */ } return joinlist; } /* * make_outerjoininfo * Build an OuterJoinInfo for the current outer join * * Inputs: * left_rels: the base Relids syntactically on outer side of join * right_rels: the base Relids syntactically on inner side of join * inner_join_rels: base Relids participating in inner joins below this one * is_full_join: what it says * clause: the outer join's join condition * * If the join is a RIGHT JOIN, left_rels and right_rels are switched by * the caller, so that left_rels is always the nonnullable side. Hence * we need only distinguish the LEFT and FULL cases. * * The node should eventually be appended to root->oj_info_list, but we * do not do that here. * * Note: we assume that this function is invoked bottom-up, so that * root->oj_info_list already contains entries for all outer joins that are * syntactically below this one. */ static OuterJoinInfo * make_outerjoininfo(PlannerInfo *root, Relids left_rels, Relids right_rels, Relids inner_join_rels, bool is_full_join, Node *clause) { OuterJoinInfo *ojinfo = makeNode(OuterJoinInfo); Relids clause_relids; Relids strict_relids; Relids min_lefthand; Relids min_righthand; ListCell *l; /* * Presently the executor cannot support FOR UPDATE/SHARE marking of rels * appearing on the nullable side of an outer join. (It's somewhat unclear * what that would mean, anyway: what should we mark when a result row is * generated from no element of the nullable relation?) So, complain if * any nullable rel is FOR UPDATE/SHARE. * * You might be wondering why this test isn't made far upstream in the * parser. It's because the parser hasn't got enough info --- consider * FOR UPDATE applied to a view. Only after rewriting and flattening do * we know whether the view contains an outer join. */ foreach(l, root->parse->rowMarks) { RowMarkClause *rc = (RowMarkClause *) lfirst(l); if (bms_is_member(rc->rti, right_rels) || (is_full_join && bms_is_member(rc->rti, left_rels))) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("SELECT FOR UPDATE/SHARE cannot be applied to the nullable side of an outer join"))); } /* this always starts out false */ ojinfo->delay_upper_joins = false; /* If it's a full join, no need to be very smart */ ojinfo->syn_lefthand = left_rels; ojinfo->syn_righthand = right_rels; ojinfo->is_full_join = is_full_join; if (is_full_join) { ojinfo->min_lefthand = left_rels; ojinfo->min_righthand = right_rels; ojinfo->lhs_strict = false; /* don't care about this */ return ojinfo; } /* * Retrieve all relids mentioned within the join clause. */ clause_relids = pull_varnos(clause); /* * For which relids is the clause strict, ie, it cannot succeed if the * rel's columns are all NULL? */ strict_relids = find_nonnullable_rels(clause); /* Remember whether the clause is strict for any LHS relations */ ojinfo->lhs_strict = bms_overlap(strict_relids, left_rels); /* * Required LHS always includes the LHS rels mentioned in the clause. * We may have to add more rels based on lower outer joins; see below. */ min_lefthand = bms_intersect(clause_relids, left_rels); /* * Similarly for required RHS. But here, we must also include any lower * inner joins, to ensure we don't try to commute with any of them. */ min_righthand = bms_int_members(bms_union(clause_relids, inner_join_rels), right_rels); foreach(l, root->oj_info_list) { OuterJoinInfo *otherinfo = (OuterJoinInfo *) lfirst(l); /* ignore full joins --- other mechanisms preserve their ordering */ if (otherinfo->is_full_join) continue; /* * For a lower OJ in our LHS, if our join condition uses the lower * join's RHS and is not strict for that rel, we must preserve the * ordering of the two OJs, so add lower OJ's full syntactic relset to * min_lefthand. (We must use its full syntactic relset, not just * its min_lefthand + min_righthand. This is because there might * be other OJs below this one that this one can commute with, * but we cannot commute with them if we don't with this one.) * * Note: I believe we have to insist on being strict for at least one * rel in the lower OJ's min_righthand, not its whole syn_righthand. */ if (bms_overlap(left_rels, otherinfo->syn_righthand) && bms_overlap(clause_relids, otherinfo->syn_righthand) && !bms_overlap(strict_relids, otherinfo->min_righthand)) { min_lefthand = bms_add_members(min_lefthand, otherinfo->syn_lefthand); min_lefthand = bms_add_members(min_lefthand, otherinfo->syn_righthand); } /* * For a lower OJ in our RHS, if our join condition does not use the * lower join's RHS and the lower OJ's join condition is strict, we * can interchange the ordering of the two OJs; otherwise we must * add lower OJ's full syntactic relset to min_righthand. * * Here, we have to consider that "our join condition" includes * any clauses that syntactically appeared above the lower OJ and * below ours; those are equivalent to degenerate clauses in our * OJ and must be treated as such. Such clauses obviously can't * reference our LHS, and they must be non-strict for the lower OJ's * RHS (else reduce_outer_joins would have reduced the lower OJ to * a plain join). Hence the other ways in which we handle clauses * within our join condition are not affected by them. The net * effect is therefore sufficiently represented by the * delay_upper_joins flag saved for us by distribute_qual_to_rels. */ if (bms_overlap(right_rels, otherinfo->syn_righthand)) { if (bms_overlap(clause_relids, otherinfo->syn_righthand) || !otherinfo->lhs_strict || otherinfo->delay_upper_joins) { min_righthand = bms_add_members(min_righthand, otherinfo->syn_lefthand); min_righthand = bms_add_members(min_righthand, otherinfo->syn_righthand); } } } /* * If we found nothing to put in min_lefthand, punt and make it the full * LHS, to avoid having an empty min_lefthand which will confuse later * processing. (We don't try to be smart about such cases, just correct.) * Likewise for min_righthand. */ if (bms_is_empty(min_lefthand)) min_lefthand = bms_copy(left_rels); if (bms_is_empty(min_righthand)) min_righthand = bms_copy(right_rels); /* Now they'd better be nonempty */ Assert(!bms_is_empty(min_lefthand)); Assert(!bms_is_empty(min_righthand)); /* Shouldn't overlap either */ Assert(!bms_overlap(min_lefthand, min_righthand)); ojinfo->min_lefthand = min_lefthand; ojinfo->min_righthand = min_righthand; return ojinfo; } /***************************************************************************** * * QUALIFICATIONS * *****************************************************************************/ /* * distribute_qual_to_rels * Add clause information to either the baserestrictinfo or joininfo list * (depending on whether the clause is a join) of each base relation * mentioned in the clause. A RestrictInfo node is created and added to * the appropriate list for each rel. Also, if the clause uses a * mergejoinable operator and is not delayed by outer-join rules, enter * the left- and right-side expressions into the query's lists of * equijoined vars. * * 'clause': the qual clause to be distributed * 'is_deduced': TRUE if the qual came from implied-equality deduction * 'below_outer_join': TRUE if the qual is from a JOIN/ON that is below the * nullable side of a higher-level outer join. * 'qualscope': set of baserels the qual's syntactic scope covers * 'ojscope': NULL if not an outer-join qual, else the minimum set of baserels * needed to form this join * 'outerjoin_nonnullable': NULL if not an outer-join qual, else the set of * baserels appearing on the outer (nonnullable) side of the join * (for FULL JOIN this includes both sides of the join, and must in fact * equal qualscope) * * 'qualscope' identifies what level of JOIN the qual came from syntactically. * 'ojscope' is needed if we decide to force the qual up to the outer-join * level, which will be ojscope not necessarily qualscope. */ static void distribute_qual_to_rels(PlannerInfo *root, Node *clause, bool is_deduced, bool below_outer_join, Relids qualscope, Relids ojscope, Relids outerjoin_nonnullable) { Relids relids; bool is_pushed_down; bool outerjoin_delayed; bool pseudoconstant = false; bool maybe_equijoin; bool maybe_outer_join; RestrictInfo *restrictinfo; RelOptInfo *rel; List *vars; /* * Retrieve all relids mentioned within the clause. */ relids = pull_varnos(clause); /* * Cross-check: clause should contain no relids not within its scope. * Otherwise the parser messed up. */ if (!bms_is_subset(relids, qualscope)) elog(ERROR, "JOIN qualification may not refer to other relations"); if (ojscope && !bms_is_subset(relids, ojscope)) elog(ERROR, "JOIN qualification may not refer to other relations"); /* * If the clause is variable-free, our normal heuristic for pushing it * down to just the mentioned rels doesn't work, because there are none. * * If the clause is an outer-join clause, we must force it to the OJ's * semantic level to preserve semantics. * * Otherwise, when the clause contains volatile functions, we force it to * be evaluated at its original syntactic level. This preserves the * expected semantics. * * When the clause contains no volatile functions either, it is actually a * pseudoconstant clause that will not change value during any one * execution of the plan, and hence can be used as a one-time qual in a * gating Result plan node. We put such a clause into the regular * RestrictInfo lists for the moment, but eventually createplan.c will * pull it out and make a gating Result node immediately above whatever * plan node the pseudoconstant clause is assigned to. It's usually best * to put a gating node as high in the plan tree as possible. If we are * not below an outer join, we can actually push the pseudoconstant qual * all the way to the top of the tree. If we are below an outer join, we * leave the qual at its original syntactic level (we could push it up to * just below the outer join, but that seems more complex than it's * worth). */ if (bms_is_empty(relids)) { if (ojscope) { /* clause is attached to outer join, eval it there */ relids = ojscope; /* mustn't use as gating qual, so don't mark pseudoconstant */ } else { /* eval at original syntactic level */ relids = qualscope; if (!contain_volatile_functions(clause)) { /* mark as gating qual */ pseudoconstant = true; /* tell createplan.c to check for gating quals */ root->hasPseudoConstantQuals = true; /* if not below outer join, push it to top of tree */ if (!below_outer_join) relids = get_relids_in_jointree((Node *) root->parse->jointree); } } } /*---------- * Check to see if clause application must be delayed by outer-join * considerations. * * A word about is_pushed_down: we mark the qual as "pushed down" if * it is (potentially) applicable at a level different from its original * syntactic level. This flag is used to distinguish OUTER JOIN ON quals * from other quals pushed down to the same joinrel. The rules are: * WHERE quals and INNER JOIN quals: is_pushed_down = true. * Non-degenerate OUTER JOIN quals: is_pushed_down = false. * Degenerate OUTER JOIN quals: is_pushed_down = true. * A "degenerate" OUTER JOIN qual is one that doesn't mention the * non-nullable side, and hence can be pushed down into the nullable side * without changing the join result. It is correct to treat it as a * regular filter condition at the level where it is evaluated. * * Note: it is not immediately obvious that a simple boolean is enough * for this: if for some reason we were to attach a degenerate qual to * its original join level, it would need to be treated as an outer join * qual there. However, this cannot happen, because all the rels the * clause mentions must be in the outer join's min_righthand, therefore * the join it needs must be formed before the outer join; and we always * attach quals to the lowest level where they can be evaluated. But * if we were ever to re-introduce a mechanism for delaying evaluation * of "expensive" quals, this area would need work. *---------- */ if (is_deduced) { /* * If the qual came from implied-equality deduction, we always * evaluate the qual at its natural semantic level. It is the * responsibility of the deducer not to create any quals that should * be delayed by outer-join rules. */ Assert(bms_equal(relids, qualscope)); Assert(!ojscope); Assert(!pseudoconstant); is_pushed_down = true; /* Needn't feed it back for more deductions */ outerjoin_delayed = false; maybe_equijoin = false; maybe_outer_join = false; } else if (bms_overlap(relids, outerjoin_nonnullable)) { /* * The qual is attached to an outer join and mentions (some of the) * rels on the nonnullable side, so it's not degenerate. Force the * qual to be evaluated exactly at the level of joining corresponding * to the outer join. We cannot let it get pushed down into the * nonnullable side, since then we'd produce no output rows, rather * than the intended single null-extended row, for any * nonnullable-side rows failing the qual. */ Assert(ojscope); relids = ojscope; is_pushed_down = false; outerjoin_delayed = true; Assert(!pseudoconstant); /* * We can't use such a clause to deduce equijoin (the left and right * sides might be unequal above the join because one of them has gone * to NULL) ... but we might be able to use it for more limited * purposes. Note: for the current uses of deductions from an * outer-join clause, it seems safe to make the deductions even when * the clause is below a higher-level outer join; so we do not check * below_outer_join here. */ maybe_equijoin = false; maybe_outer_join = true; } else { /* * Normal qual clause or degenerate outer-join clause. Either way, * we can mark it as pushed-down. * * For a pushed-down qual, we can evaluate the qual as soon as (1) * we have all the rels it mentions, and (2) we are at or above any * outer joins that can null any of these rels and are below the * syntactic location of the given qual. We must enforce (2) because * pushing down such a clause below the OJ might cause the OJ to emit * null-extended rows that should not have been formed, or that should * have been rejected by the clause. (This is only an issue for * non-strict quals, since if we can prove a qual mentioning only * nullable rels is strict, we'd have reduced the outer join to an * inner join in reduce_outer_joins().) * * To enforce (2), scan the oj_info_list and merge the required-relid * sets of any such OJs into the clause's own reference list. At the * time we are called, the oj_info_list contains only outer joins * below this qual. We have to repeat the scan until no new relids * get added; this ensures that the qual is suitably delayed regardless * of the order in which OJs get executed. As an example, if we have * one OJ with LHS=A, RHS=B, and one with LHS=B, RHS=C, it is implied * that these can be done in either order; if the B/C join is done * first then the join to A can null C, so a qual actually mentioning * only C cannot be applied below the join to A. */ bool found_some; is_pushed_down = true; outerjoin_delayed = false; do { ListCell *l; found_some = false; foreach(l, root->oj_info_list) { OuterJoinInfo *ojinfo = (OuterJoinInfo *) lfirst(l); /* do we have any nullable rels of this OJ? */ if (bms_overlap(relids, ojinfo->min_righthand) || (ojinfo->is_full_join && bms_overlap(relids, ojinfo->min_lefthand))) { /* yes; do we have all its rels? */ if (!bms_is_subset(ojinfo->min_lefthand, relids) || !bms_is_subset(ojinfo->min_righthand, relids)) { /* no, so add them in */ relids = bms_add_members(relids, ojinfo->min_lefthand); relids = bms_add_members(relids, ojinfo->min_righthand); outerjoin_delayed = true; /* we'll need another iteration */ found_some = true; } /* set delay_upper_joins if needed */ if (!ojinfo->is_full_join && bms_overlap(relids, ojinfo->min_lefthand)) ojinfo->delay_upper_joins = true; } } } while (found_some); if (outerjoin_delayed) { /* Should still be a subset of current scope ... */ Assert(bms_is_subset(relids, qualscope)); /* * Because application of the qual will be delayed by outer join, * we mustn't assume its vars are equal everywhere. */ maybe_equijoin = false; } else { /* * Qual is not delayed by any lower outer-join restriction. If it * is not itself below or within an outer join, we can consider it * "valid everywhere", so consider feeding it to the equijoin * machinery. (If it is within an outer join, we can't consider * it "valid everywhere": once the contained variables have gone * to NULL, we'd be asserting things like NULL = NULL, which is * not true.) */ if (!below_outer_join && outerjoin_nonnullable == NULL) maybe_equijoin = true; else maybe_equijoin = false; } /* Since it doesn't mention the LHS, it's certainly not an OJ clause */ maybe_outer_join = false; } /* * Build the RestrictInfo node itself. */ restrictinfo = make_restrictinfo((Expr *) clause, is_pushed_down, outerjoin_delayed, pseudoconstant, relids); /* * Figure out where to attach it. */ switch (bms_membership(relids)) { case BMS_SINGLETON: /* * There is only one relation participating in 'clause', so * 'clause' is a restriction clause for that relation. */ rel = find_base_rel(root, bms_singleton_member(relids)); /* * Check for a "mergejoinable" clause even though it's not a join * clause. This is so that we can recognize that "a.x = a.y" * makes x and y eligible to be considered equal, even when they * belong to the same rel. Without this, we would not recognize * that "a.x = a.y AND a.x = b.z AND a.y = c.q" allows us to * consider z and q equal after their rels are joined. */ check_mergejoinable(restrictinfo); /* * If the clause was deduced from implied equality, check to see * whether it is redundant with restriction clauses we already * have for this rel. Note we cannot apply this check to * user-written clauses, since we haven't found the canonical * pathkey sets yet while processing user clauses. (NB: no * comparable check is done in the join-clause case; redundancy * will be detected when the join clause is moved into a join * rel's restriction list.) */ if (!is_deduced || !qual_is_redundant(root, restrictinfo, rel->baserestrictinfo)) { /* Add clause to rel's restriction list */ rel->baserestrictinfo = lappend(rel->baserestrictinfo, restrictinfo); } break; case BMS_MULTIPLE: /* * 'clause' is a join clause, since there is more than one rel in * the relid set. */ /* * Check for hash or mergejoinable operators. * * We don't bother setting the hashjoin info if we're not going to * need it. We do want to know about mergejoinable ops in all * cases, however, because we use mergejoinable ops for other * purposes such as detecting redundant clauses. */ check_mergejoinable(restrictinfo); if (enable_hashjoin) check_hashjoinable(restrictinfo); /* * Add clause to the join lists of all the relevant relations. */ add_join_clause_to_rels(root, restrictinfo, relids); /* * Add vars used in the join clause to targetlists of their * relations, so that they will be emitted by the plan nodes that * scan those relations (else they won't be available at the join * node!). */ vars = pull_var_clause(clause, false); add_vars_to_targetlist(root, vars, relids); list_free(vars); break; default: /* * 'clause' references no rels, and therefore we have no place to * attach it. Shouldn't get here if callers are working properly. */ elog(ERROR, "cannot cope with variable-free clause"); break; } /* * If the clause has a mergejoinable operator, we may be able to deduce * more things from it under the principle of transitivity. * * If it is not an outer-join qualification nor bubbled up due to an outer * join, then the two sides represent equivalent PathKeyItems for path * keys: any path that is sorted by one side will also be sorted by the * other (as soon as the two rels are joined, that is). Pass such clauses * to add_equijoined_keys. * * If it is a left or right outer-join qualification that relates the two * sides of the outer join (no funny business like leftvar1 = leftvar2 + * rightvar), we add it to root->left_join_clauses or * root->right_join_clauses according to which side the nonnullable * variable appears on. * * If it is a full outer-join qualification, we add it to * root->full_join_clauses. (Ideally we'd discard cases that aren't * leftvar = rightvar, as we do for left/right joins, but this routine * doesn't have the info needed to do that; and the current usage of the * full_join_clauses list doesn't require that, so it's not currently * worth complicating this routine's API to make it possible.) */ if (restrictinfo->mergejoinoperator != InvalidOid) { if (maybe_equijoin) add_equijoined_keys(root, restrictinfo); else if (maybe_outer_join && restrictinfo->can_join) { if (bms_is_subset(restrictinfo->left_relids, outerjoin_nonnullable) && !bms_overlap(restrictinfo->right_relids, outerjoin_nonnullable)) { /* we have outervar = innervar */ root->left_join_clauses = lappend(root->left_join_clauses, restrictinfo); } else if (bms_is_subset(restrictinfo->right_relids, outerjoin_nonnullable) && !bms_overlap(restrictinfo->left_relids, outerjoin_nonnullable)) { /* we have innervar = outervar */ root->right_join_clauses = lappend(root->right_join_clauses, restrictinfo); } else if (bms_equal(outerjoin_nonnullable, qualscope)) { /* FULL JOIN (above tests cannot match in this case) */ root->full_join_clauses = lappend(root->full_join_clauses, restrictinfo); } } } } /* * process_implied_equality * Check to see whether we already have a restrictinfo item that says * item1 = item2, and create one if not; or if delete_it is true, * remove any such restrictinfo item. * * This processing is a consequence of transitivity of mergejoin equality: * if we have mergejoinable clauses A = B and B = C, we can deduce A = C * (where = is an appropriate mergejoinable operator). See path/pathkeys.c * for more details. */ void process_implied_equality(PlannerInfo *root, Node *item1, Node *item2, Oid sortop1, Oid sortop2, Relids item1_relids, Relids item2_relids, bool delete_it) { Relids relids; BMS_Membership membership; RelOptInfo *rel1; List *restrictlist; ListCell *itm; Oid ltype, rtype; Operator eq_operator; Form_pg_operator pgopform; Expr *clause; /* Get set of relids referenced in the two expressions */ relids = bms_union(item1_relids, item2_relids); membership = bms_membership(relids); /* * generate_implied_equalities() shouldn't call me on two constants. */ Assert(membership != BMS_EMPTY_SET); /* * If the exprs involve a single rel, we need to look at that rel's * baserestrictinfo list. If multiple rels, we can scan the joininfo list * of any of 'em. */ if (membership == BMS_SINGLETON) { rel1 = find_base_rel(root, bms_singleton_member(relids)); restrictlist = rel1->baserestrictinfo; } else { Relids other_rels; int first_rel; /* Copy relids, find and remove one member */ other_rels = bms_copy(relids); first_rel = bms_first_member(other_rels); bms_free(other_rels); rel1 = find_base_rel(root, first_rel); restrictlist = rel1->joininfo; } /* * Scan to see if equality is already known. If so, we're done in the add * case, and done after removing it in the delete case. */ foreach(itm, restrictlist) { RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(itm); Node *left, *right; if (restrictinfo->mergejoinoperator == InvalidOid) continue; /* ignore non-mergejoinable clauses */ /* We now know the restrictinfo clause is a binary opclause */ left = get_leftop(restrictinfo->clause); right = get_rightop(restrictinfo->clause); if ((equal(item1, left) && equal(item2, right)) || (equal(item2, left) && equal(item1, right))) { /* found a matching clause */ if (delete_it) { if (membership == BMS_SINGLETON) { /* delete it from local restrictinfo list */ rel1->baserestrictinfo = list_delete_ptr(rel1->baserestrictinfo, restrictinfo); } else { /* let joininfo.c do it */ remove_join_clause_from_rels(root, restrictinfo, relids); } } return; /* done */ } } /* Didn't find it. Done if deletion requested */ if (delete_it) return; /* * This equality is new information, so construct a clause representing it * to add to the query data structures. */ ltype = exprType(item1); rtype = exprType(item2); eq_operator = compatible_oper(NULL, list_make1(makeString("=")), ltype, rtype, true, -1); if (!HeapTupleIsValid(eq_operator)) { /* * Would it be safe to just not add the equality to the query if we * have no suitable equality operator for the combination of * datatypes? NO, because sortkey selection may screw up anyway. */ ereport(ERROR, (errcode(ERRCODE_UNDEFINED_FUNCTION), errmsg("could not identify an equality operator for types %s and %s", format_type_be(ltype), format_type_be(rtype)))); } pgopform = (Form_pg_operator) GETSTRUCT(eq_operator); /* * Let's just make sure this appears to be a compatible operator. */ if (pgopform->oprlsortop != sortop1 || pgopform->oprrsortop != sortop2 || pgopform->oprresult != BOOLOID) ereport(ERROR, (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION), errmsg("equality operator for types %s and %s should be merge-joinable, but isn't", format_type_be(ltype), format_type_be(rtype)))); /* * Now we can build the new clause. Copy to ensure it shares no * substructure with original (this is necessary in case there are * subselects in there...) */ clause = make_opclause(oprid(eq_operator), /* opno */ BOOLOID, /* opresulttype */ false, /* opretset */ (Expr *) copyObject(item1), (Expr *) copyObject(item2)); ReleaseSysCache(eq_operator); /* * Push the new clause into all the appropriate restrictinfo lists. */ distribute_qual_to_rels(root, (Node *) clause, true, false, relids, NULL, NULL); } /* * qual_is_redundant * Detect whether an implied-equality qual that turns out to be a * restriction clause for a single base relation is redundant with * already-known restriction clauses for that rel. This occurs with, * for example, * SELECT * FROM tab WHERE f1 = f2 AND f2 = f3; * We need to suppress the redundant condition to avoid computing * too-small selectivity, not to mention wasting time at execution. * * Note: quals of the form "var = const" are never considered redundant, * only those of the form "var = var". This is needed because when we * have constants in an implied-equality set, we use a different strategy * that suppresses all "var = var" deductions. We must therefore keep * all the "var = const" quals. */ static bool qual_is_redundant(PlannerInfo *root, RestrictInfo *restrictinfo, List *restrictlist) { Node *newleft; Node *newright; List *oldquals; ListCell *olditem; List *equalexprs; bool someadded; /* Never redundant unless vars appear on both sides */ if (bms_is_empty(restrictinfo->left_relids) || bms_is_empty(restrictinfo->right_relids)) return false; newleft = get_leftop(restrictinfo->clause); newright = get_rightop(restrictinfo->clause); /* * Set cached pathkeys. NB: it is okay to do this now because this * routine is only invoked while we are generating implied equalities. * Therefore, the equi_key_list is already complete and so we can * correctly determine canonical pathkeys. */ cache_mergeclause_pathkeys(root, restrictinfo); /* If different, say "not redundant" (should never happen) */ if (restrictinfo->left_pathkey != restrictinfo->right_pathkey) return false; /* * Scan existing quals to find those referencing same pathkeys. Usually * there will be few, if any, so build a list of just the interesting * ones. */ oldquals = NIL; foreach(olditem, restrictlist) { RestrictInfo *oldrinfo = (RestrictInfo *) lfirst(olditem); if (oldrinfo->mergejoinoperator != InvalidOid) { cache_mergeclause_pathkeys(root, oldrinfo); if (restrictinfo->left_pathkey == oldrinfo->left_pathkey && restrictinfo->right_pathkey == oldrinfo->right_pathkey) oldquals = lcons(oldrinfo, oldquals); } } if (oldquals == NIL) return false; /* * Now, we want to develop a list of exprs that are known equal to the * left side of the new qual. We traverse the old-quals list repeatedly * to transitively expand the exprs list. If at any point we find we can * reach the right-side expr of the new qual, we are done. We give up * when we can't expand the equalexprs list any more. */ equalexprs = list_make1(newleft); do { someadded = false; /* cannot use foreach here because of possible list_delete */ olditem = list_head(oldquals); while (olditem) { RestrictInfo *oldrinfo = (RestrictInfo *) lfirst(olditem); Node *oldleft = get_leftop(oldrinfo->clause); Node *oldright = get_rightop(oldrinfo->clause); Node *newguy = NULL; /* must advance olditem before list_delete possibly pfree's it */ olditem = lnext(olditem); if (list_member(equalexprs, oldleft)) newguy = oldright; else if (list_member(equalexprs, oldright)) newguy = oldleft; else continue; if (equal(newguy, newright)) return true; /* we proved new clause is redundant */ equalexprs = lcons(newguy, equalexprs); someadded = true; /* * Remove this qual from list, since we don't need it anymore. */ oldquals = list_delete_ptr(oldquals, oldrinfo); } } while (someadded); return false; /* it's not redundant */ } /***************************************************************************** * * CHECKS FOR MERGEJOINABLE AND HASHJOINABLE CLAUSES * *****************************************************************************/ /* * check_mergejoinable * If the restrictinfo's clause is mergejoinable, set the mergejoin * info fields in the restrictinfo. * * Currently, we support mergejoin for binary opclauses where * the operator is a mergejoinable operator. The arguments can be * anything --- as long as there are no volatile functions in them. */ static void check_mergejoinable(RestrictInfo *restrictinfo) { Expr *clause = restrictinfo->clause; Oid opno, leftOp, rightOp; if (restrictinfo->pseudoconstant) return; if (!is_opclause(clause)) return; if (list_length(((OpExpr *) clause)->args) != 2) return; opno = ((OpExpr *) clause)->opno; if (op_mergejoinable(opno, &leftOp, &rightOp) && !contain_volatile_functions((Node *) clause)) { restrictinfo->mergejoinoperator = opno; restrictinfo->left_sortop = leftOp; restrictinfo->right_sortop = rightOp; } } /* * check_hashjoinable * If the restrictinfo's clause is hashjoinable, set the hashjoin * info fields in the restrictinfo. * * Currently, we support hashjoin for binary opclauses where * the operator is a hashjoinable operator. The arguments can be * anything --- as long as there are no volatile functions in them. */ static void check_hashjoinable(RestrictInfo *restrictinfo) { Expr *clause = restrictinfo->clause; Oid opno; if (restrictinfo->pseudoconstant) return; if (!is_opclause(clause)) return; if (list_length(((OpExpr *) clause)->args) != 2) return; opno = ((OpExpr *) clause)->opno; if (op_hashjoinable(opno) && !contain_volatile_functions((Node *) clause)) restrictinfo->hashjoinoperator = opno; }