/*------------------------------------------------------------------------- * * prepjointree.c * Planner preprocessing for subqueries and join tree manipulation. * * NOTE: the intended sequence for invoking these operations is * pull_up_IN_clauses * inline_set_returning_functions * pull_up_subqueries * do expression preprocessing (including flattening JOIN alias vars) * reduce_outer_joins * * * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.50 2008/03/18 22:04:14 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "nodes/makefuncs.h" #include "optimizer/clauses.h" #include "optimizer/prep.h" #include "optimizer/subselect.h" #include "optimizer/tlist.h" #include "optimizer/var.h" #include "parser/parse_expr.h" #include "parser/parsetree.h" #include "rewrite/rewriteManip.h" typedef struct reduce_outer_joins_state { Relids relids; /* base relids within this subtree */ bool contains_outer; /* does subtree contain outer join(s)? */ List *sub_states; /* List of states for subtree components */ } reduce_outer_joins_state; static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, bool below_outer_join, bool append_rel_member); static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte); static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex, Query *setOpQuery); static void make_setop_translation_lists(Query *query, Index newvarno, List **col_mappings, List **translated_vars); static bool is_simple_subquery(Query *subquery); static bool is_simple_union_all(Query *subquery); static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes); static bool has_nullable_targetlist(Query *subquery); static bool is_safe_append_member(Query *subquery); static void resolvenew_in_jointree(Node *jtnode, int varno, RangeTblEntry *rte, List *subtlist); static reduce_outer_joins_state *reduce_outer_joins_pass1(Node *jtnode); static void reduce_outer_joins_pass2(Node *jtnode, reduce_outer_joins_state *state, PlannerInfo *root, Relids nonnullable_rels); static void fix_in_clause_relids(List *in_info_list, int varno, Relids subrelids); static void fix_append_rel_relids(List *append_rel_list, int varno, Relids subrelids); static Node *find_jointree_node_for_rel(Node *jtnode, int relid); /* * pull_up_IN_clauses * Attempt to pull up top-level IN clauses to be treated like joins. * * A clause "foo IN (sub-SELECT)" appearing at the top level of WHERE can * be processed by pulling the sub-SELECT up to become a rangetable entry * and handling the implied equality comparisons as join operators (with * special join rules). * This optimization *only* works at the top level of WHERE, because * it cannot distinguish whether the IN ought to return FALSE or NULL in * cases involving NULL inputs. This routine searches for such clauses * and does the necessary parsetree transformations if any are found. * * This routine has to run before preprocess_expression(), so the WHERE * clause is not yet reduced to implicit-AND format. That means we need * to recursively search through explicit AND clauses, which are * probably only binary ANDs. We stop as soon as we hit a non-AND item. * * Returns the possibly-modified version of the given qual-tree node. */ Node * pull_up_IN_clauses(PlannerInfo *root, Node *node) { if (node == NULL) return NULL; if (IsA(node, SubLink)) { SubLink *sublink = (SubLink *) node; Node *subst; /* Is it a convertible IN clause? If not, return it as-is */ subst = convert_IN_to_join(root, sublink); if (subst == NULL) return node; return subst; } if (and_clause(node)) { List *newclauses = NIL; ListCell *l; foreach(l, ((BoolExpr *) node)->args) { Node *oldclause = (Node *) lfirst(l); newclauses = lappend(newclauses, pull_up_IN_clauses(root, oldclause)); } return (Node *) make_andclause(newclauses); } /* Stop if not an AND */ return node; } /* * inline_set_returning_functions * Attempt to "inline" set-returning functions in the FROM clause. * * If an RTE_FUNCTION rtable entry invokes a set-returning function that * contains just a simple SELECT, we can convert the rtable entry to an * RTE_SUBQUERY entry exposing the SELECT directly. This is especially * useful if the subquery can then be "pulled up" for further optimization, * but we do it even if not, to reduce executor overhead. * * This has to be done before we have started to do any optimization of * subqueries, else any such steps wouldn't get applied to subqueries * obtained via inlining. However, we do it after pull_up_IN_clauses * so that we can inline any functions used in IN subselects. * * Like most of the planner, this feels free to scribble on its input data * structure. */ void inline_set_returning_functions(PlannerInfo *root) { ListCell *rt; foreach(rt, root->parse->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt); if (rte->rtekind == RTE_FUNCTION) { Query *funcquery; /* Check safety of expansion, and expand if possible */ funcquery = inline_set_returning_function(root, rte->funcexpr); if (funcquery) { /* Successful expansion, replace the rtable entry */ rte->rtekind = RTE_SUBQUERY; rte->subquery = funcquery; rte->funcexpr = NULL; rte->funccoltypes = NIL; rte->funccoltypmods = NIL; } } } } /* * pull_up_subqueries * Look for subqueries in the rangetable that can be pulled up into * the parent query. If the subquery has no special features like * grouping/aggregation then we can merge it into the parent's jointree. * Also, subqueries that are simple UNION ALL structures can be * converted into "append relations". * * below_outer_join is true if this jointree node is within the nullable * side of an outer join. This restricts what we can do. * * append_rel_member is true if we are looking at a member subquery of * an append relation. This puts some different restrictions on what * we can do. * * A tricky aspect of this code is that if we pull up a subquery we have * to replace Vars that reference the subquery's outputs throughout the * parent query, including quals attached to jointree nodes above the one * we are currently processing! We handle this by being careful not to * change the jointree structure while recursing: no nodes other than * subquery RangeTblRef entries will be replaced. Also, we can't turn * ResolveNew loose on the whole jointree, because it'll return a mutated * copy of the tree; we have to invoke it just on the quals, instead. */ Node * pull_up_subqueries(PlannerInfo *root, Node *jtnode, bool below_outer_join, bool append_rel_member) { if (jtnode == NULL) return NULL; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; RangeTblEntry *rte = rt_fetch(varno, root->parse->rtable); /* * Is this a subquery RTE, and if so, is the subquery simple enough to * pull up? (If not, do nothing at this node.) * * If we are inside an outer join, only pull up subqueries whose * targetlists are nullable --- otherwise substituting their tlist * entries for upper Var references would do the wrong thing (the * results wouldn't become NULL when they're supposed to). * * XXX This could be improved by generating pseudo-variables for such * expressions; we'd have to figure out how to get the pseudo- * variables evaluated at the right place in the modified plan tree. * Fix it someday. * * If we are looking at an append-relation member, we can't pull it up * unless is_safe_append_member says so. */ if (rte->rtekind == RTE_SUBQUERY && is_simple_subquery(rte->subquery) && (!below_outer_join || has_nullable_targetlist(rte->subquery)) && (!append_rel_member || is_safe_append_member(rte->subquery))) return pull_up_simple_subquery(root, jtnode, rte, below_outer_join, append_rel_member); /* * Alternatively, is it a simple UNION ALL subquery? If so, flatten * into an "append relation". We can do this regardless of * nullability considerations since this transformation does not * result in propagating non-Var expressions into upper levels of the * query. * * It's also safe to do this regardless of whether this query is * itself an appendrel member. (If you're thinking we should try to * flatten the two levels of appendrel together, you're right; but we * handle that in set_append_rel_pathlist, not here.) */ if (rte->rtekind == RTE_SUBQUERY && is_simple_union_all(rte->subquery)) return pull_up_simple_union_all(root, jtnode, rte); } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; Assert(!append_rel_member); foreach(l, f->fromlist) lfirst(l) = pull_up_subqueries(root, lfirst(l), below_outer_join, false); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; Assert(!append_rel_member); /* Recurse, being careful to tell myself when inside outer join */ switch (j->jointype) { case JOIN_INNER: j->larg = pull_up_subqueries(root, j->larg, below_outer_join, false); j->rarg = pull_up_subqueries(root, j->rarg, below_outer_join, false); break; case JOIN_LEFT: j->larg = pull_up_subqueries(root, j->larg, below_outer_join, false); j->rarg = pull_up_subqueries(root, j->rarg, true, false); break; case JOIN_FULL: j->larg = pull_up_subqueries(root, j->larg, true, false); j->rarg = pull_up_subqueries(root, j->rarg, true, false); break; case JOIN_RIGHT: j->larg = pull_up_subqueries(root, j->larg, true, false); j->rarg = pull_up_subqueries(root, j->rarg, below_outer_join, false); break; default: elog(ERROR, "unrecognized join type: %d", (int) j->jointype); break; } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return jtnode; } /* * pull_up_simple_subquery * Attempt to pull up a single simple subquery. * * jtnode is a RangeTblRef that has been tentatively identified as a simple * subquery by pull_up_subqueries. We return the replacement jointree node, * or jtnode itself if we determine that the subquery can't be pulled up after * all. */ static Node * pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, bool below_outer_join, bool append_rel_member) { Query *parse = root->parse; int varno = ((RangeTblRef *) jtnode)->rtindex; Query *subquery; PlannerInfo *subroot; int rtoffset; List *subtlist; ListCell *rt; /* * Need a modifiable copy of the subquery to hack on. Even if we didn't * sometimes choose not to pull up below, we must do this to avoid * problems if the same subquery is referenced from multiple jointree * items (which can't happen normally, but might after rule rewriting). */ subquery = copyObject(rte->subquery); /* * Create a PlannerInfo data structure for this subquery. * * NOTE: the next few steps should match the first processing in * subquery_planner(). Can we refactor to avoid code duplication, or * would that just make things uglier? */ subroot = makeNode(PlannerInfo); subroot->parse = subquery; subroot->glob = root->glob; subroot->query_level = root->query_level; subroot->planner_cxt = CurrentMemoryContext; subroot->init_plans = NIL; subroot->eq_classes = NIL; subroot->in_info_list = NIL; subroot->append_rel_list = NIL; /* * Pull up any IN clauses within the subquery's WHERE, so that we don't * leave unoptimized INs behind. */ if (subquery->hasSubLinks) subquery->jointree->quals = pull_up_IN_clauses(subroot, subquery->jointree->quals); /* * Similarly, inline any set-returning functions in its rangetable. */ inline_set_returning_functions(subroot); /* * Recursively pull up the subquery's subqueries, so that * pull_up_subqueries' processing is complete for its jointree and * rangetable. * * Note: below_outer_join = false is correct here even if we are within an * outer join in the upper query; the lower query starts with a clean * slate for outer-join semantics. Likewise, we say we aren't handling an * appendrel member. */ subquery->jointree = (FromExpr *) pull_up_subqueries(subroot, (Node *) subquery->jointree, false, false); /* * Now we must recheck whether the subquery is still simple enough to pull * up. If not, abandon processing it. * * We don't really need to recheck all the conditions involved, but it's * easier just to keep this "if" looking the same as the one in * pull_up_subqueries. */ if (is_simple_subquery(subquery) && (!below_outer_join || has_nullable_targetlist(subquery)) && (!append_rel_member || is_safe_append_member(subquery))) { /* good to go */ } else { /* * Give up, return unmodified RangeTblRef. * * Note: The work we just did will be redone when the subquery gets * planned on its own. Perhaps we could avoid that by storing the * modified subquery back into the rangetable, but I'm not gonna risk * it now. */ return jtnode; } /* * Adjust level-0 varnos in subquery so that we can append its rangetable * to upper query's. We have to fix the subquery's in_info_list and * append_rel_list, as well. */ rtoffset = list_length(parse->rtable); OffsetVarNodes((Node *) subquery, rtoffset, 0); OffsetVarNodes((Node *) subroot->in_info_list, rtoffset, 0); OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0); /* * Upper-level vars in subquery are now one level closer to their parent * than before. */ IncrementVarSublevelsUp((Node *) subquery, -1, 1); IncrementVarSublevelsUp((Node *) subroot->in_info_list, -1, 1); IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1); /* * Replace all of the top query's references to the subquery's outputs * with copies of the adjusted subtlist items, being careful not to * replace any of the jointree structure. (This'd be a lot cleaner if we * could use query_tree_mutator.) */ subtlist = subquery->targetList; parse->targetList = (List *) ResolveNew((Node *) parse->targetList, varno, 0, rte, subtlist, CMD_SELECT, 0); parse->returningList = (List *) ResolveNew((Node *) parse->returningList, varno, 0, rte, subtlist, CMD_SELECT, 0); resolvenew_in_jointree((Node *) parse->jointree, varno, rte, subtlist); Assert(parse->setOperations == NULL); parse->havingQual = ResolveNew(parse->havingQual, varno, 0, rte, subtlist, CMD_SELECT, 0); root->in_info_list = (List *) ResolveNew((Node *) root->in_info_list, varno, 0, rte, subtlist, CMD_SELECT, 0); root->append_rel_list = (List *) ResolveNew((Node *) root->append_rel_list, varno, 0, rte, subtlist, CMD_SELECT, 0); foreach(rt, parse->rtable) { RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(rt); if (otherrte->rtekind == RTE_JOIN) otherrte->joinaliasvars = (List *) ResolveNew((Node *) otherrte->joinaliasvars, varno, 0, rte, subtlist, CMD_SELECT, 0); } /* * Now append the adjusted rtable entries to upper query. (We hold off * until after fixing the upper rtable entries; no point in running that * code on the subquery ones too.) */ parse->rtable = list_concat(parse->rtable, subquery->rtable); /* * Pull up any FOR UPDATE/SHARE markers, too. (OffsetVarNodes already * adjusted the marker rtindexes, so just concat the lists.) */ parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks); /* * We also have to fix the relid sets of any parent InClauseInfo nodes. * (This could perhaps be done by ResolveNew, but it would clutter that * routine's API unreasonably.) * * Likewise, relids appearing in AppendRelInfo nodes have to be fixed (but * we took care of their translated_vars lists above). We already checked * that this won't require introducing multiple subrelids into the * single-slot AppendRelInfo structs. */ if (root->in_info_list || root->append_rel_list) { Relids subrelids; subrelids = get_relids_in_jointree((Node *) subquery->jointree); fix_in_clause_relids(root->in_info_list, varno, subrelids); fix_append_rel_relids(root->append_rel_list, varno, subrelids); } /* * And now add any subquery InClauseInfos and AppendRelInfos to our lists. */ root->in_info_list = list_concat(root->in_info_list, subroot->in_info_list); root->append_rel_list = list_concat(root->append_rel_list, subroot->append_rel_list); /* * We don't have to do the equivalent bookkeeping for outer-join info, * because that hasn't been set up yet. */ Assert(root->oj_info_list == NIL); Assert(subroot->oj_info_list == NIL); /* * Miscellaneous housekeeping. */ parse->hasSubLinks |= subquery->hasSubLinks; /* subquery won't be pulled up if it hasAggs, so no work there */ /* * Return the adjusted subquery jointree to replace the RangeTblRef entry * in parent's jointree. */ return (Node *) subquery->jointree; } /* * pull_up_simple_union_all * Pull up a single simple UNION ALL subquery. * * jtnode is a RangeTblRef that has been identified as a simple UNION ALL * subquery by pull_up_subqueries. We pull up the leaf subqueries and * build an "append relation" for the union set. The result value is just * jtnode, since we don't actually need to change the query jointree. */ static Node * pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte) { int varno = ((RangeTblRef *) jtnode)->rtindex; Query *subquery = rte->subquery; /* * Recursively scan the subquery's setOperations tree and copy the leaf * subqueries into the parent rangetable. Add AppendRelInfo nodes for * them to the parent's append_rel_list, too. */ Assert(subquery->setOperations); pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery); /* * Mark the parent as an append relation. */ rte->inh = true; return jtnode; } /* * pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all * * Note that setOpQuery is the Query containing the setOp node, whose rtable * is where to look up the RTE if setOp is a RangeTblRef. This is *not* the * same as root->parse, which is the top-level Query we are pulling up into. * parentRTindex is the appendrel parent's index in root->parse->rtable. */ static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex, Query *setOpQuery) { if (IsA(setOp, RangeTblRef)) { RangeTblRef *rtr = (RangeTblRef *) setOp; RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable); Query *subquery; int childRTindex; AppendRelInfo *appinfo; Query *parse = root->parse; /* * Make a modifiable copy of the child RTE and contained query. */ rte = copyObject(rte); subquery = rte->subquery; Assert(subquery != NULL); /* * Upper-level vars in subquery are now one level closer to their * parent than before. We don't have to worry about offsetting * varnos, though, because any such vars must refer to stuff above the * level of the query we are pulling into. */ IncrementVarSublevelsUp((Node *) subquery, -1, 1); /* * Attach child RTE to parent rtable. */ parse->rtable = lappend(parse->rtable, rte); childRTindex = list_length(parse->rtable); /* * Build a suitable AppendRelInfo, and attach to parent's list. */ appinfo = makeNode(AppendRelInfo); appinfo->parent_relid = parentRTindex; appinfo->child_relid = childRTindex; appinfo->parent_reltype = InvalidOid; appinfo->child_reltype = InvalidOid; make_setop_translation_lists(setOpQuery, childRTindex, &appinfo->col_mappings, &appinfo->translated_vars); appinfo->parent_reloid = InvalidOid; root->append_rel_list = lappend(root->append_rel_list, appinfo); /* * Recursively apply pull_up_subqueries to the new child RTE. (We * must build the AppendRelInfo first, because this will modify it.) * Note that we can pass below_outer_join = false even if we're * actually under an outer join, because the child's expressions * aren't going to propagate up above the join. */ rtr = makeNode(RangeTblRef); rtr->rtindex = childRTindex; (void) pull_up_subqueries(root, (Node *) rtr, false, true); } else if (IsA(setOp, SetOperationStmt)) { SetOperationStmt *op = (SetOperationStmt *) setOp; /* Recurse to reach leaf queries */ pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery); pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery); } else { elog(ERROR, "unrecognized node type: %d", (int) nodeTag(setOp)); } } /* * make_setop_translation_lists * Build the lists of translations from parent Vars to child Vars for * a UNION ALL member. We need both a column number mapping list * and a list of Vars representing the child columns. */ static void make_setop_translation_lists(Query *query, Index newvarno, List **col_mappings, List **translated_vars) { List *numbers = NIL; List *vars = NIL; ListCell *l; foreach(l, query->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(l); if (tle->resjunk) continue; numbers = lappend_int(numbers, tle->resno); vars = lappend(vars, makeVar(newvarno, tle->resno, exprType((Node *) tle->expr), exprTypmod((Node *) tle->expr), 0)); } *col_mappings = numbers; *translated_vars = vars; } /* * is_simple_subquery * Check a subquery in the range table to see if it's simple enough * to pull up into the parent query. */ static bool is_simple_subquery(Query *subquery) { /* * Let's just make sure it's a valid subselect ... */ if (!IsA(subquery, Query) || subquery->commandType != CMD_SELECT || subquery->utilityStmt != NULL || subquery->intoClause != NULL) elog(ERROR, "subquery is bogus"); /* * Can't currently pull up a query with setops (unless it's simple UNION * ALL, which is handled by a different code path). Maybe after querytree * redesign... */ if (subquery->setOperations) return false; /* * Can't pull up a subquery involving grouping, aggregation, sorting, or * limiting. */ if (subquery->hasAggs || subquery->groupClause || subquery->havingQual || subquery->sortClause || subquery->distinctClause || subquery->limitOffset || subquery->limitCount) return false; /* * Don't pull up a subquery that has any set-returning functions in its * targetlist. Otherwise we might well wind up inserting set-returning * functions into places where they mustn't go, such as quals of higher * queries. */ if (expression_returns_set((Node *) subquery->targetList)) return false; /* * Don't pull up a subquery that has any volatile functions in its * targetlist. Otherwise we might introduce multiple evaluations of these * functions, if they get copied to multiple places in the upper query, * leading to surprising results. */ if (contain_volatile_functions((Node *) subquery->targetList)) return false; /* * Hack: don't try to pull up a subquery with an empty jointree. * query_planner() will correctly generate a Result plan for a jointree * that's totally empty, but I don't think the right things happen if an * empty FromExpr appears lower down in a jointree. Not worth working hard * on this, just to collapse SubqueryScan/Result into Result... */ if (subquery->jointree->fromlist == NIL) return false; return true; } /* * is_simple_union_all * Check a subquery to see if it's a simple UNION ALL. * * We require all the setops to be UNION ALL (no mixing) and there can't be * any datatype coercions involved, ie, all the leaf queries must emit the * same datatypes. */ static bool is_simple_union_all(Query *subquery) { SetOperationStmt *topop; /* Let's just make sure it's a valid subselect ... */ if (!IsA(subquery, Query) || subquery->commandType != CMD_SELECT || subquery->utilityStmt != NULL || subquery->intoClause != NULL) elog(ERROR, "subquery is bogus"); /* Is it a set-operation query at all? */ topop = (SetOperationStmt *) subquery->setOperations; if (!topop) return false; Assert(IsA(topop, SetOperationStmt)); /* Can't handle ORDER BY, LIMIT/OFFSET, or locking */ if (subquery->sortClause || subquery->limitOffset || subquery->limitCount || subquery->rowMarks) return false; /* Recursively check the tree of set operations */ return is_simple_union_all_recurse((Node *) topop, subquery, topop->colTypes); } static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes) { if (IsA(setOp, RangeTblRef)) { RangeTblRef *rtr = (RangeTblRef *) setOp; RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable); Query *subquery = rte->subquery; Assert(subquery != NULL); /* Leaf nodes are OK if they match the toplevel column types */ /* We don't have to compare typmods here */ return tlist_same_datatypes(subquery->targetList, colTypes, true); } else if (IsA(setOp, SetOperationStmt)) { SetOperationStmt *op = (SetOperationStmt *) setOp; /* Must be UNION ALL */ if (op->op != SETOP_UNION || !op->all) return false; /* Recurse to check inputs */ return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) && is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes); } else { elog(ERROR, "unrecognized node type: %d", (int) nodeTag(setOp)); return false; /* keep compiler quiet */ } } /* * has_nullable_targetlist * Check a subquery in the range table to see if all the non-junk * targetlist items are simple variables or strict functions of simple * variables (and, hence, will correctly go to NULL when examined above * the point of an outer join). * * NOTE: it would be correct (and useful) to ignore output columns that aren't * actually referenced by the enclosing query ... but we do not have that * information available at this point. */ static bool has_nullable_targetlist(Query *subquery) { ListCell *l; foreach(l, subquery->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(l); /* ignore resjunk columns */ if (tle->resjunk) continue; /* Must contain a Var of current level */ if (!contain_vars_of_level((Node *) tle->expr, 0)) return false; /* Must not contain any non-strict constructs */ if (contain_nonstrict_functions((Node *) tle->expr)) return false; /* This one's OK, keep scanning */ } return true; } /* * is_safe_append_member * Check a subquery that is a leaf of a UNION ALL appendrel to see if it's * safe to pull up. */ static bool is_safe_append_member(Query *subquery) { FromExpr *jtnode; ListCell *l; /* * It's only safe to pull up the child if its jointree contains exactly * one RTE, else the AppendRelInfo data structure breaks. The one base RTE * could be buried in several levels of FromExpr, however. * * Also, the child can't have any WHERE quals because there's no place to * put them in an appendrel. (This is a bit annoying...) If we didn't * need to check this, we'd just test whether get_relids_in_jointree() * yields a singleton set, to be more consistent with the coding of * fix_append_rel_relids(). */ jtnode = subquery->jointree; while (IsA(jtnode, FromExpr)) { if (jtnode->quals != NULL) return false; if (list_length(jtnode->fromlist) != 1) return false; jtnode = linitial(jtnode->fromlist); } if (!IsA(jtnode, RangeTblRef)) return false; /* * XXX For the moment we also have to insist that the subquery's tlist * includes only simple Vars. This is pretty annoying, but fixing it * seems to require nontrivial changes --- mainly because joinrel tlists * are presently assumed to contain only Vars. Perhaps a pseudo-variable * mechanism similar to the one speculated about in pull_up_subqueries' * comments would help? FIXME someday. */ foreach(l, subquery->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(l); if (tle->resjunk) continue; if (!(tle->expr && IsA(tle->expr, Var))) return false; } return true; } /* * Helper routine for pull_up_subqueries: do ResolveNew on every expression * in the jointree, without changing the jointree structure itself. Ugly, * but there's no other way... */ static void resolvenew_in_jointree(Node *jtnode, int varno, RangeTblEntry *rte, List *subtlist) { if (jtnode == NULL) return; if (IsA(jtnode, RangeTblRef)) { /* nothing to do here */ } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) resolvenew_in_jointree(lfirst(l), varno, rte, subtlist); f->quals = ResolveNew(f->quals, varno, 0, rte, subtlist, CMD_SELECT, 0); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; resolvenew_in_jointree(j->larg, varno, rte, subtlist); resolvenew_in_jointree(j->rarg, varno, rte, subtlist); j->quals = ResolveNew(j->quals, varno, 0, rte, subtlist, CMD_SELECT, 0); /* * We don't bother to update the colvars list, since it won't be used * again ... */ } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /* * reduce_outer_joins * Attempt to reduce outer joins to plain inner joins. * * The idea here is that given a query like * SELECT ... FROM a LEFT JOIN b ON (...) WHERE b.y = 42; * we can reduce the LEFT JOIN to a plain JOIN if the "=" operator in WHERE * is strict. The strict operator will always return NULL, causing the outer * WHERE to fail, on any row where the LEFT JOIN filled in NULLs for b's * columns. Therefore, there's no need for the join to produce null-extended * rows in the first place --- which makes it a plain join not an outer join. * (This scenario may not be very likely in a query written out by hand, but * it's reasonably likely when pushing quals down into complex views.) * * More generally, an outer join can be reduced in strength if there is a * strict qual above it in the qual tree that constrains a Var from the * nullable side of the join to be non-null. (For FULL joins this applies * to each side separately.) * * To ease recognition of strict qual clauses, we require this routine to be * run after expression preprocessing (i.e., qual canonicalization and JOIN * alias-var expansion). */ void reduce_outer_joins(PlannerInfo *root) { reduce_outer_joins_state *state; /* * To avoid doing strictness checks on more quals than necessary, we want * to stop descending the jointree as soon as there are no outer joins * below our current point. This consideration forces a two-pass process. * The first pass gathers information about which base rels appear below * each side of each join clause, and about whether there are outer * join(s) below each side of each join clause. The second pass examines * qual clauses and changes join types as it descends the tree. */ state = reduce_outer_joins_pass1((Node *) root->parse->jointree); /* planner.c shouldn't have called me if no outer joins */ if (state == NULL || !state->contains_outer) elog(ERROR, "so where are the outer joins?"); reduce_outer_joins_pass2((Node *) root->parse->jointree, state, root, NULL); } /* * reduce_outer_joins_pass1 - phase 1 data collection * * Returns a state node describing the given jointree node. */ static reduce_outer_joins_state * reduce_outer_joins_pass1(Node *jtnode) { reduce_outer_joins_state *result; result = (reduce_outer_joins_state *) palloc(sizeof(reduce_outer_joins_state)); result->relids = NULL; result->contains_outer = false; result->sub_states = NIL; if (jtnode == NULL) return result; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; result->relids = bms_make_singleton(varno); } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) { reduce_outer_joins_state *sub_state; sub_state = reduce_outer_joins_pass1(lfirst(l)); result->relids = bms_add_members(result->relids, sub_state->relids); result->contains_outer |= sub_state->contains_outer; result->sub_states = lappend(result->sub_states, sub_state); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; reduce_outer_joins_state *sub_state; /* join's own RT index is not wanted in result->relids */ if (IS_OUTER_JOIN(j->jointype)) result->contains_outer = true; sub_state = reduce_outer_joins_pass1(j->larg); result->relids = bms_add_members(result->relids, sub_state->relids); result->contains_outer |= sub_state->contains_outer; result->sub_states = lappend(result->sub_states, sub_state); sub_state = reduce_outer_joins_pass1(j->rarg); result->relids = bms_add_members(result->relids, sub_state->relids); result->contains_outer |= sub_state->contains_outer; result->sub_states = lappend(result->sub_states, sub_state); } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return result; } /* * reduce_outer_joins_pass2 - phase 2 processing * * jtnode: current jointree node * state: state data collected by phase 1 for this node * root: toplevel planner state * nonnullable_rels: set of base relids forced non-null by upper quals */ static void reduce_outer_joins_pass2(Node *jtnode, reduce_outer_joins_state *state, PlannerInfo *root, Relids nonnullable_rels) { /* * pass 2 should never descend as far as an empty subnode or base rel, * because it's only called on subtrees marked as contains_outer. */ if (jtnode == NULL) elog(ERROR, "reached empty jointree"); if (IsA(jtnode, RangeTblRef)) elog(ERROR, "reached base rel"); else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; ListCell *s; Relids pass_nonnullable; /* Scan quals to see if we can add any nonnullability constraints */ pass_nonnullable = find_nonnullable_rels(f->quals); pass_nonnullable = bms_add_members(pass_nonnullable, nonnullable_rels); /* And recurse --- but only into interesting subtrees */ Assert(list_length(f->fromlist) == list_length(state->sub_states)); forboth(l, f->fromlist, s, state->sub_states) { reduce_outer_joins_state *sub_state = lfirst(s); if (sub_state->contains_outer) reduce_outer_joins_pass2(lfirst(l), sub_state, root, pass_nonnullable); } bms_free(pass_nonnullable); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; int rtindex = j->rtindex; JoinType jointype = j->jointype; reduce_outer_joins_state *left_state = linitial(state->sub_states); reduce_outer_joins_state *right_state = lsecond(state->sub_states); /* Can we simplify this join? */ switch (jointype) { case JOIN_LEFT: if (bms_overlap(nonnullable_rels, right_state->relids)) jointype = JOIN_INNER; break; case JOIN_RIGHT: if (bms_overlap(nonnullable_rels, left_state->relids)) jointype = JOIN_INNER; break; case JOIN_FULL: if (bms_overlap(nonnullable_rels, left_state->relids)) { if (bms_overlap(nonnullable_rels, right_state->relids)) jointype = JOIN_INNER; else jointype = JOIN_LEFT; } else { if (bms_overlap(nonnullable_rels, right_state->relids)) jointype = JOIN_RIGHT; } break; default: break; } if (jointype != j->jointype) { /* apply the change to both jointree node and RTE */ RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable); Assert(rte->rtekind == RTE_JOIN); Assert(rte->jointype == j->jointype); rte->jointype = j->jointype = jointype; } /* Only recurse if there's more to do below here */ if (left_state->contains_outer || right_state->contains_outer) { Relids local_nonnullable; Relids pass_nonnullable; /* * If this join is (now) inner, we can add any nonnullability * constraints its quals provide to those we got from above. But * if it is outer, we can only pass down the local constraints * into the nullable side, because an outer join never eliminates * any rows from its non-nullable side. If it's a FULL join then * it doesn't eliminate anything from either side. */ if (jointype != JOIN_FULL) { local_nonnullable = find_nonnullable_rels(j->quals); local_nonnullable = bms_add_members(local_nonnullable, nonnullable_rels); } else local_nonnullable = NULL; /* no use in calculating it */ if (left_state->contains_outer) { if (jointype == JOIN_INNER || jointype == JOIN_RIGHT) pass_nonnullable = local_nonnullable; else pass_nonnullable = nonnullable_rels; reduce_outer_joins_pass2(j->larg, left_state, root, pass_nonnullable); } if (right_state->contains_outer) { if (jointype == JOIN_INNER || jointype == JOIN_LEFT) pass_nonnullable = local_nonnullable; else pass_nonnullable = nonnullable_rels; reduce_outer_joins_pass2(j->rarg, right_state, root, pass_nonnullable); } bms_free(local_nonnullable); } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /* * fix_in_clause_relids: update RT-index sets of InClauseInfo nodes * * When we pull up a subquery, any InClauseInfo references to the subquery's * RT index have to be replaced by the set of substituted relids. * * We assume we may modify the InClauseInfo nodes in-place. */ static void fix_in_clause_relids(List *in_info_list, int varno, Relids subrelids) { ListCell *l; foreach(l, in_info_list) { InClauseInfo *ininfo = (InClauseInfo *) lfirst(l); if (bms_is_member(varno, ininfo->lefthand)) { ininfo->lefthand = bms_del_member(ininfo->lefthand, varno); ininfo->lefthand = bms_add_members(ininfo->lefthand, subrelids); } if (bms_is_member(varno, ininfo->righthand)) { ininfo->righthand = bms_del_member(ininfo->righthand, varno); ininfo->righthand = bms_add_members(ininfo->righthand, subrelids); } } } /* * fix_append_rel_relids: update RT-index fields of AppendRelInfo nodes * * When we pull up a subquery, any AppendRelInfo references to the subquery's * RT index have to be replaced by the substituted relid (and there had better * be only one). * * We assume we may modify the AppendRelInfo nodes in-place. */ static void fix_append_rel_relids(List *append_rel_list, int varno, Relids subrelids) { ListCell *l; int subvarno = -1; /* * We only want to extract the member relid once, but we mustn't fail * immediately if there are multiple members; it could be that none of the * AppendRelInfo nodes refer to it. So compute it on first use. Note that * bms_singleton_member will complain if set is not singleton. */ foreach(l, append_rel_list) { AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l); /* The parent_relid shouldn't ever be a pullup target */ Assert(appinfo->parent_relid != varno); if (appinfo->child_relid == varno) { if (subvarno < 0) subvarno = bms_singleton_member(subrelids); appinfo->child_relid = subvarno; } } } /* * get_relids_in_jointree: get set of base RT indexes present in a jointree */ Relids get_relids_in_jointree(Node *jtnode) { Relids result = NULL; if (jtnode == NULL) return result; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; result = bms_make_singleton(varno); } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) { result = bms_join(result, get_relids_in_jointree(lfirst(l))); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; /* join's own RT index is not wanted in result */ result = get_relids_in_jointree(j->larg); result = bms_join(result, get_relids_in_jointree(j->rarg)); } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return result; } /* * get_relids_for_join: get set of base RT indexes making up a join */ Relids get_relids_for_join(PlannerInfo *root, int joinrelid) { Node *jtnode; jtnode = find_jointree_node_for_rel((Node *) root->parse->jointree, joinrelid); if (!jtnode) elog(ERROR, "could not find join node %d", joinrelid); return get_relids_in_jointree(jtnode); } /* * find_jointree_node_for_rel: locate jointree node for a base or join RT index * * Returns NULL if not found */ static Node * find_jointree_node_for_rel(Node *jtnode, int relid) { if (jtnode == NULL) return NULL; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; if (relid == varno) return jtnode; } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) { jtnode = find_jointree_node_for_rel(lfirst(l), relid); if (jtnode) return jtnode; } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; if (relid == j->rtindex) return jtnode; jtnode = find_jointree_node_for_rel(j->larg, relid); if (jtnode) return jtnode; jtnode = find_jointree_node_for_rel(j->rarg, relid); if (jtnode) return jtnode; } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return NULL; }