/*------------------------------------------------------------------------- * * prepjointree.c * Planner preprocessing for subqueries and join tree manipulation. * * NOTE: the intended sequence for invoking these operations is * replace_empty_jointree * pull_up_sublinks * preprocess_function_rtes * expand_virtual_generated_columns * pull_up_subqueries * flatten_simple_union_all * do expression preprocessing (including flattening JOIN alias vars) * reduce_outer_joins * remove_useless_result_rtes * * * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/optimizer/prep/prepjointree.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/table.h" #include "catalog/pg_type.h" #include "funcapi.h" #include "miscadmin.h" #include "nodes/makefuncs.h" #include "nodes/multibitmapset.h" #include "nodes/nodeFuncs.h" #include "optimizer/clauses.h" #include "optimizer/optimizer.h" #include "optimizer/placeholder.h" #include "optimizer/prep.h" #include "optimizer/subselect.h" #include "optimizer/tlist.h" #include "parser/parse_relation.h" #include "parser/parsetree.h" #include "rewrite/rewriteHandler.h" #include "rewrite/rewriteManip.h" #include "utils/rel.h" typedef struct nullingrel_info { /* * For each leaf RTE, nullingrels[rti] is the set of relids of outer joins * that potentially null that RTE. */ Relids *nullingrels; /* Length of range table (maximum index in nullingrels[]) */ int rtlength; /* used only for assertion checks */ } nullingrel_info; /* Options for wrapping an expression for identification purposes */ typedef enum ReplaceWrapOption { REPLACE_WRAP_NONE, /* no expressions need to be wrapped */ REPLACE_WRAP_ALL, /* all expressions need to be wrapped */ REPLACE_WRAP_VARFREE, /* variable-free expressions need to be * wrapped */ } ReplaceWrapOption; typedef struct pullup_replace_vars_context { PlannerInfo *root; List *targetlist; /* tlist of subquery being pulled up */ RangeTblEntry *target_rte; /* RTE of subquery */ int result_relation; /* the index of the result relation in the * rewritten query */ Relids relids; /* relids within subquery, as numbered after * pullup (set only if target_rte->lateral) */ nullingrel_info *nullinfo; /* per-RTE nullingrel info (set only if * target_rte->lateral) */ bool *outer_hasSubLinks; /* -> outer query's hasSubLinks */ int varno; /* varno of subquery */ ReplaceWrapOption wrap_option; /* do we need certain outputs to be PHVs? */ Node **rv_cache; /* cache for results with PHVs */ } pullup_replace_vars_context; typedef struct reduce_outer_joins_pass1_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_pass1_state; typedef struct reduce_outer_joins_pass2_state { Relids inner_reduced; /* OJ relids reduced to plain inner joins */ List *partial_reduced; /* List of partially reduced FULL joins */ } reduce_outer_joins_pass2_state; typedef struct reduce_outer_joins_partial_state { int full_join_rti; /* RT index of a formerly-FULL join */ Relids unreduced_side; /* relids in its still-nullable side */ } reduce_outer_joins_partial_state; static Node *pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode, Relids *relids); static Node *pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node, Node **jtlink1, Relids available_rels1, Node **jtlink2, Relids available_rels2); static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode, JoinExpr *lowest_outer_join, AppendRelInfo *containing_appendrel); static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, JoinExpr *lowest_outer_join, AppendRelInfo *containing_appendrel); 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, int childRToffset); static void make_setop_translation_list(Query *query, int newvarno, AppendRelInfo *appinfo); static bool is_simple_subquery(PlannerInfo *root, Query *subquery, RangeTblEntry *rte, JoinExpr *lowest_outer_join); static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte); static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte); static Node *pull_up_constant_function(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, AppendRelInfo *containing_appendrel); static bool is_simple_union_all(Query *subquery); static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes); static bool is_safe_append_member(Query *subquery); static bool jointree_contains_lateral_outer_refs(PlannerInfo *root, Node *jtnode, bool restricted, Relids safe_upper_varnos); static void perform_pullup_replace_vars(PlannerInfo *root, pullup_replace_vars_context *rvcontext, AppendRelInfo *containing_appendrel); static void replace_vars_in_jointree(Node *jtnode, pullup_replace_vars_context *context); static Node *pullup_replace_vars(Node *expr, pullup_replace_vars_context *context); static Node *pullup_replace_vars_callback(Var *var, replace_rte_variables_context *context); static Query *pullup_replace_vars_subquery(Query *query, pullup_replace_vars_context *context); static reduce_outer_joins_pass1_state *reduce_outer_joins_pass1(Node *jtnode); static void reduce_outer_joins_pass2(Node *jtnode, reduce_outer_joins_pass1_state *state1, reduce_outer_joins_pass2_state *state2, PlannerInfo *root, Relids nonnullable_rels, List *forced_null_vars); static void report_reduced_full_join(reduce_outer_joins_pass2_state *state2, int rtindex, Relids relids); static Node *remove_useless_results_recurse(PlannerInfo *root, Node *jtnode, Node **parent_quals, Relids *dropped_outer_joins); static int get_result_relid(PlannerInfo *root, Node *jtnode); static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc); static bool find_dependent_phvs(PlannerInfo *root, int varno); static bool find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno); static void substitute_phv_relids(Node *node, int varno, Relids subrelids); static void fix_append_rel_relids(PlannerInfo *root, int varno, Relids subrelids); static Node *find_jointree_node_for_rel(Node *jtnode, int relid); static nullingrel_info *get_nullingrels(Query *parse); static void get_nullingrels_recurse(Node *jtnode, Relids upper_nullingrels, nullingrel_info *info); /* * transform_MERGE_to_join * Replace a MERGE's jointree to also include the target relation. */ void transform_MERGE_to_join(Query *parse) { RangeTblEntry *joinrte; JoinExpr *joinexpr; bool have_action[NUM_MERGE_MATCH_KINDS]; JoinType jointype; int joinrti; List *vars; RangeTblRef *rtr; FromExpr *target; Node *source; int sourcerti; if (parse->commandType != CMD_MERGE) return; /* XXX probably bogus */ vars = NIL; /* * Work out what kind of join is required. If there any WHEN NOT MATCHED * BY SOURCE/TARGET actions, an outer join is required so that we process * all unmatched tuples from the source and/or target relations. * Otherwise, we can use an inner join. */ have_action[MERGE_WHEN_MATCHED] = false; have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] = false; have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET] = false; foreach_node(MergeAction, action, parse->mergeActionList) { if (action->commandType != CMD_NOTHING) have_action[action->matchKind] = true; } if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] && have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET]) jointype = JOIN_FULL; else if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE]) jointype = JOIN_LEFT; else if (have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET]) jointype = JOIN_RIGHT; else jointype = JOIN_INNER; /* Manufacture a join RTE to use. */ joinrte = makeNode(RangeTblEntry); joinrte->rtekind = RTE_JOIN; joinrte->jointype = jointype; joinrte->joinmergedcols = 0; joinrte->joinaliasvars = vars; joinrte->joinleftcols = NIL; /* MERGE does not allow JOIN USING */ joinrte->joinrightcols = NIL; /* ditto */ joinrte->join_using_alias = NULL; joinrte->alias = NULL; joinrte->eref = makeAlias("*MERGE*", NIL); joinrte->lateral = false; joinrte->inh = false; joinrte->inFromCl = true; /* * Add completed RTE to pstate's range table list, so that we know its * index. */ parse->rtable = lappend(parse->rtable, joinrte); joinrti = list_length(parse->rtable); /* * Create a JOIN between the target and the source relation. * * Here the target is identified by parse->mergeTargetRelation. For a * regular table, this will equal parse->resultRelation, but for a * trigger-updatable view, it will be the expanded view subquery that we * need to pull data from. * * The source relation is in parse->jointree->fromlist, but any quals in * parse->jointree->quals are restrictions on the target relation (if the * target relation is an auto-updatable view). */ /* target rel, with any quals */ rtr = makeNode(RangeTblRef); rtr->rtindex = parse->mergeTargetRelation; target = makeFromExpr(list_make1(rtr), parse->jointree->quals); /* source rel (expect exactly one -- see transformMergeStmt()) */ Assert(list_length(parse->jointree->fromlist) == 1); source = linitial(parse->jointree->fromlist); /* * index of source rel (expect either a RangeTblRef or a JoinExpr -- see * transformFromClauseItem()). */ if (IsA(source, RangeTblRef)) sourcerti = ((RangeTblRef *) source)->rtindex; else if (IsA(source, JoinExpr)) sourcerti = ((JoinExpr *) source)->rtindex; else { elog(ERROR, "unrecognized source node type: %d", (int) nodeTag(source)); sourcerti = 0; /* keep compiler quiet */ } /* Join the source and target */ joinexpr = makeNode(JoinExpr); joinexpr->jointype = jointype; joinexpr->isNatural = false; joinexpr->larg = (Node *) target; joinexpr->rarg = source; joinexpr->usingClause = NIL; joinexpr->join_using_alias = NULL; joinexpr->quals = parse->mergeJoinCondition; joinexpr->alias = NULL; joinexpr->rtindex = joinrti; /* Make the new join be the sole entry in the query's jointree */ parse->jointree->fromlist = list_make1(joinexpr); parse->jointree->quals = NULL; /* * If necessary, mark parse->targetlist entries that refer to the target * as nullable by the join. Normally the targetlist will be empty for a * MERGE, but if the target is a trigger-updatable view, it will contain a * whole-row Var referring to the expanded view query. */ if (parse->targetList != NIL && (jointype == JOIN_RIGHT || jointype == JOIN_FULL)) parse->targetList = (List *) add_nulling_relids((Node *) parse->targetList, bms_make_singleton(parse->mergeTargetRelation), bms_make_singleton(joinrti)); /* * If the source relation is on the outer side of the join, mark any * source relation Vars in the join condition, actions, and RETURNING list * as nullable by the join. These Vars will be added to the targetlist by * preprocess_targetlist(), so it's important to mark them correctly here. * * It might seem that this is not necessary for Vars in the join * condition, since it is inside the join, but it is also needed above the * join (in the ModifyTable node) to distinguish between the MATCHED and * NOT MATCHED BY SOURCE cases -- see ExecMergeMatched(). Note that this * creates a modified copy of the join condition, for use above the join, * without modifying the original join condition, inside the join. */ if (jointype == JOIN_LEFT || jointype == JOIN_FULL) { parse->mergeJoinCondition = add_nulling_relids(parse->mergeJoinCondition, bms_make_singleton(sourcerti), bms_make_singleton(joinrti)); foreach_node(MergeAction, action, parse->mergeActionList) { action->qual = add_nulling_relids(action->qual, bms_make_singleton(sourcerti), bms_make_singleton(joinrti)); action->targetList = (List *) add_nulling_relids((Node *) action->targetList, bms_make_singleton(sourcerti), bms_make_singleton(joinrti)); } parse->returningList = (List *) add_nulling_relids((Node *) parse->returningList, bms_make_singleton(sourcerti), bms_make_singleton(joinrti)); } /* * If there are any WHEN NOT MATCHED BY SOURCE actions, the executor will * use the join condition to distinguish between MATCHED and NOT MATCHED * BY SOURCE cases. Otherwise, it's no longer needed, and we set it to * NULL, saving cycles during planning and execution. * * We need to be careful though: the executor evaluates this condition * using the output of the join subplan node, which nulls the output from * the source relation when the join condition doesn't match. That risks * producing incorrect results when rechecking using a "non-strict" join * condition, such as "src.col IS NOT DISTINCT FROM tgt.col". To guard * against that, we add an additional "src IS NOT NULL" check to the join * condition, so that it does the right thing when performing a recheck * based on the output of the join subplan. */ if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE]) { Var *var; NullTest *ntest; /* source wholerow Var (nullable by the new join) */ var = makeWholeRowVar(rt_fetch(sourcerti, parse->rtable), sourcerti, 0, false); var->varnullingrels = bms_make_singleton(joinrti); /* "src IS NOT NULL" check */ ntest = makeNode(NullTest); ntest->arg = (Expr *) var; ntest->nulltesttype = IS_NOT_NULL; ntest->argisrow = false; ntest->location = -1; /* combine it with the original join condition */ parse->mergeJoinCondition = (Node *) make_and_qual((Node *) ntest, parse->mergeJoinCondition); } else parse->mergeJoinCondition = NULL; /* join condition not needed */ } /* * replace_empty_jointree * If the Query's jointree is empty, replace it with a dummy RTE_RESULT * relation. * * By doing this, we can avoid a bunch of corner cases that formerly existed * for SELECTs with omitted FROM clauses. An example is that a subquery * with empty jointree previously could not be pulled up, because that would * have resulted in an empty relid set, making the subquery not uniquely * identifiable for join or PlaceHolderVar processing. * * Unlike most other functions in this file, this function doesn't recurse; * we rely on other processing to invoke it on sub-queries at suitable times. */ void replace_empty_jointree(Query *parse) { RangeTblEntry *rte; Index rti; RangeTblRef *rtr; /* Nothing to do if jointree is already nonempty */ if (parse->jointree->fromlist != NIL) return; /* We mustn't change it in the top level of a setop tree, either */ if (parse->setOperations) return; /* Create suitable RTE */ rte = makeNode(RangeTblEntry); rte->rtekind = RTE_RESULT; rte->eref = makeAlias("*RESULT*", NIL); /* Add it to rangetable */ parse->rtable = lappend(parse->rtable, rte); rti = list_length(parse->rtable); /* And jam a reference into the jointree */ rtr = makeNode(RangeTblRef); rtr->rtindex = rti; parse->jointree->fromlist = list_make1(rtr); } /* * pull_up_sublinks * Attempt to pull up ANY and EXISTS SubLinks to be treated as * semijoins or anti-semijoins. * * A clause "foo op ANY (sub-SELECT)" can be processed by pulling the * sub-SELECT up to become a rangetable entry and treating the implied * comparisons as quals of a semijoin. However, this optimization *only* * works at the top level of WHERE or a JOIN/ON clause, because we cannot * distinguish whether the ANY ought to return FALSE or NULL in cases * involving NULL inputs. Also, in an outer join's ON clause we can only * do this if the sublink is degenerate (ie, references only the nullable * side of the join). In that case it is legal to push the semijoin * down into the nullable side of the join. If the sublink references any * nonnullable-side variables then it would have to be evaluated as part * of the outer join, which makes things way too complicated. * * Under similar conditions, EXISTS and NOT EXISTS clauses can be handled * by pulling up the sub-SELECT and creating a semijoin or anti-semijoin. * * 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 quals * clauses are not yet reduced to implicit-AND format, and are not guaranteed * to be AND/OR-flat either. That means we need to recursively search through * explicit AND clauses. We stop as soon as we hit a non-AND item. */ void pull_up_sublinks(PlannerInfo *root) { Node *jtnode; Relids relids; /* Begin recursion through the jointree */ jtnode = pull_up_sublinks_jointree_recurse(root, (Node *) root->parse->jointree, &relids); /* * root->parse->jointree must always be a FromExpr, so insert a dummy one * if we got a bare RangeTblRef or JoinExpr out of the recursion. */ if (IsA(jtnode, FromExpr)) root->parse->jointree = (FromExpr *) jtnode; else root->parse->jointree = makeFromExpr(list_make1(jtnode), NULL); } /* * Recurse through jointree nodes for pull_up_sublinks() * * In addition to returning the possibly-modified jointree node, we return * a relids set of the contained rels into *relids. */ static Node * pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode, Relids *relids) { /* Since this function recurses, it could be driven to stack overflow. */ check_stack_depth(); if (jtnode == NULL) { *relids = NULL; } else if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; *relids = bms_make_singleton(varno); /* jtnode is returned unmodified */ } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; List *newfromlist = NIL; Relids frelids = NULL; FromExpr *newf; Node *jtlink; ListCell *l; /* First, recurse to process children and collect their relids */ foreach(l, f->fromlist) { Node *newchild; Relids childrelids; newchild = pull_up_sublinks_jointree_recurse(root, lfirst(l), &childrelids); newfromlist = lappend(newfromlist, newchild); frelids = bms_join(frelids, childrelids); } /* Build the replacement FromExpr; no quals yet */ newf = makeFromExpr(newfromlist, NULL); /* Set up a link representing the rebuilt jointree */ jtlink = (Node *) newf; /* Now process qual --- all children are available for use */ newf->quals = pull_up_sublinks_qual_recurse(root, f->quals, &jtlink, frelids, NULL, NULL); /* * Note that the result will be either newf, or a stack of JoinExprs * with newf at the base. We rely on subsequent optimization steps to * flatten this and rearrange the joins as needed. * * Although we could include the pulled-up subqueries in the returned * relids, there's no need since upper quals couldn't refer to their * outputs anyway. */ *relids = frelids; jtnode = jtlink; } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j; Relids leftrelids; Relids rightrelids; Node *jtlink; /* * Make a modifiable copy of join node, but don't bother copying its * subnodes (yet). */ j = (JoinExpr *) palloc(sizeof(JoinExpr)); memcpy(j, jtnode, sizeof(JoinExpr)); jtlink = (Node *) j; /* Recurse to process children and collect their relids */ j->larg = pull_up_sublinks_jointree_recurse(root, j->larg, &leftrelids); j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &rightrelids); /* * Now process qual, showing appropriate child relids as available, * and attach any pulled-up jointree items at the right place. In the * inner-join case we put new JoinExprs above the existing one (much * as for a FromExpr-style join). In outer-join cases the new * JoinExprs must go into the nullable side of the outer join. The * point of the available_rels machinations is to ensure that we only * pull up quals for which that's okay. * * We don't expect to see any pre-existing JOIN_SEMI, JOIN_ANTI, * JOIN_RIGHT_SEMI, or JOIN_RIGHT_ANTI jointypes here. */ switch (j->jointype) { case JOIN_INNER: j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &jtlink, bms_union(leftrelids, rightrelids), NULL, NULL); break; case JOIN_LEFT: j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->rarg, rightrelids, NULL, NULL); break; case JOIN_FULL: /* can't do anything with full-join quals */ break; case JOIN_RIGHT: j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->larg, leftrelids, NULL, NULL); break; default: elog(ERROR, "unrecognized join type: %d", (int) j->jointype); break; } /* * Although we could include the pulled-up subqueries in the returned * relids, there's no need since upper quals couldn't refer to their * outputs anyway. But we *do* need to include the join's own rtindex * because we haven't yet collapsed join alias variables, so upper * levels would mistakenly think they couldn't use references to this * join. */ *relids = bms_join(leftrelids, rightrelids); if (j->rtindex) *relids = bms_add_member(*relids, j->rtindex); jtnode = jtlink; } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return jtnode; } /* * Recurse through top-level qual nodes for pull_up_sublinks() * * jtlink1 points to the link in the jointree where any new JoinExprs should * be inserted if they reference available_rels1 (i.e., available_rels1 * denotes the relations present underneath jtlink1). Optionally, jtlink2 can * point to a second link where new JoinExprs should be inserted if they * reference available_rels2 (pass NULL for both those arguments if not used). * Note that SubLinks referencing both sets of variables cannot be optimized. * If we find multiple pull-up-able SubLinks, they'll get stacked onto jtlink1 * and/or jtlink2 in the order we encounter them. We rely on subsequent * optimization to rearrange the stack if appropriate. * * Returns the replacement qual node, or NULL if the qual should be removed. */ static Node * pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node, Node **jtlink1, Relids available_rels1, Node **jtlink2, Relids available_rels2) { if (node == NULL) return NULL; if (IsA(node, SubLink)) { SubLink *sublink = (SubLink *) node; JoinExpr *j; Relids child_rels; /* Is it a convertible ANY or EXISTS clause? */ if (sublink->subLinkType == ANY_SUBLINK) { ScalarArrayOpExpr *saop; if ((saop = convert_VALUES_to_ANY(root, sublink->testexpr, (Query *) sublink->subselect)) != NULL) /* * The VALUES sequence was simplified. Nothing more to do * here. */ return (Node *) saop; if ((j = convert_ANY_sublink_to_join(root, sublink, available_rels1)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink1; *jtlink1 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Any inserted * joins can get stacked onto either j->larg or j->rarg, * depending on which rels they reference. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->larg, available_rels1, &j->rarg, child_rels); /* Return NULL representing constant TRUE */ return NULL; } if (available_rels2 != NULL && (j = convert_ANY_sublink_to_join(root, sublink, available_rels2)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink2; *jtlink2 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Any inserted * joins can get stacked onto either j->larg or j->rarg, * depending on which rels they reference. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->larg, available_rels2, &j->rarg, child_rels); /* Return NULL representing constant TRUE */ return NULL; } } else if (sublink->subLinkType == EXISTS_SUBLINK) { if ((j = convert_EXISTS_sublink_to_join(root, sublink, false, available_rels1)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink1; *jtlink1 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Any inserted * joins can get stacked onto either j->larg or j->rarg, * depending on which rels they reference. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->larg, available_rels1, &j->rarg, child_rels); /* Return NULL representing constant TRUE */ return NULL; } if (available_rels2 != NULL && (j = convert_EXISTS_sublink_to_join(root, sublink, false, available_rels2)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink2; *jtlink2 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Any inserted * joins can get stacked onto either j->larg or j->rarg, * depending on which rels they reference. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->larg, available_rels2, &j->rarg, child_rels); /* Return NULL representing constant TRUE */ return NULL; } } /* Else return it unmodified */ return node; } if (is_notclause(node)) { /* If the immediate argument of NOT is EXISTS, try to convert */ SubLink *sublink = (SubLink *) get_notclausearg((Expr *) node); JoinExpr *j; Relids child_rels; if (sublink && IsA(sublink, SubLink)) { if (sublink->subLinkType == EXISTS_SUBLINK) { if ((j = convert_EXISTS_sublink_to_join(root, sublink, true, available_rels1)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink1; *jtlink1 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Because * we are underneath a NOT, we can't pull up sublinks that * reference the left-hand stuff, but it's still okay to * pull up sublinks referencing j->rarg. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->rarg, child_rels, NULL, NULL); /* Return NULL representing constant TRUE */ return NULL; } if (available_rels2 != NULL && (j = convert_EXISTS_sublink_to_join(root, sublink, true, available_rels2)) != NULL) { /* Yes; insert the new join node into the join tree */ j->larg = *jtlink2; *jtlink2 = (Node *) j; /* Recursively process pulled-up jointree nodes */ j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg, &child_rels); /* * Now recursively process the pulled-up quals. Because * we are underneath a NOT, we can't pull up sublinks that * reference the left-hand stuff, but it's still okay to * pull up sublinks referencing j->rarg. */ j->quals = pull_up_sublinks_qual_recurse(root, j->quals, &j->rarg, child_rels, NULL, NULL); /* Return NULL representing constant TRUE */ return NULL; } } } /* Else return it unmodified */ return node; } if (is_andclause(node)) { /* Recurse into AND clause */ List *newclauses = NIL; ListCell *l; foreach(l, ((BoolExpr *) node)->args) { Node *oldclause = (Node *) lfirst(l); Node *newclause; newclause = pull_up_sublinks_qual_recurse(root, oldclause, jtlink1, available_rels1, jtlink2, available_rels2); if (newclause) newclauses = lappend(newclauses, newclause); } /* We might have got back fewer clauses than we started with */ if (newclauses == NIL) return NULL; else if (list_length(newclauses) == 1) return (Node *) linitial(newclauses); else return (Node *) make_andclause(newclauses); } /* Stop if not an AND */ return node; } /* * preprocess_function_rtes * Constant-simplify any FUNCTION RTEs in the FROM clause, and then * attempt to "inline" any that are set-returning functions. * * 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_sublinks * so that we can inline any functions used in SubLink subselects. * * The reason for applying const-simplification at this stage is that * (a) we'd need to do it anyway to inline a SRF, and (b) by doing it now, * we can be sure that pull_up_constant_function() will see constants * if there are constants to be seen. This approach also guarantees * that every FUNCTION RTE has been const-simplified, allowing planner.c's * preprocess_expression() to skip doing it again. * * Like most of the planner, this feels free to scribble on its input data * structure. */ void preprocess_function_rtes(PlannerInfo *root) { ListCell *rt; foreach(rt, root->parse->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt); if (rte->rtekind == RTE_FUNCTION) { Query *funcquery; /* Apply const-simplification */ rte->functions = (List *) eval_const_expressions(root, (Node *) rte->functions); /* Check safety of expansion, and expand if possible */ funcquery = inline_set_returning_function(root, rte); if (funcquery) { /* Successful expansion, convert the RTE to a subquery */ rte->rtekind = RTE_SUBQUERY; rte->subquery = funcquery; rte->security_barrier = false; /* * Clear fields that should not be set in a subquery RTE. * However, we leave rte->functions filled in for the moment, * in case makeWholeRowVar needs to consult it. We'll clear * it in setrefs.c (see add_rte_to_flat_rtable) so that this * abuse of the data structure doesn't escape the planner. */ rte->funcordinality = false; } } } } /* * expand_virtual_generated_columns * Expand all virtual generated column references in a query. * * This scans the rangetable for relations with virtual generated columns, and * replaces all Var nodes in the query that reference these columns with the * generation expressions. Note that we do not descend into subqueries; that * is taken care of when the subqueries are planned. * * This has to be done after we have pulled up any SubLinks within the query's * quals; otherwise any virtual generated column references within the SubLinks * that should be transformed into joins wouldn't get expanded. * * Returns a modified copy of the query tree, if any relations with virtual * generated columns are present. */ Query * expand_virtual_generated_columns(PlannerInfo *root) { Query *parse = root->parse; int rt_index; ListCell *lc; rt_index = 0; foreach(lc, parse->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc); Relation rel; TupleDesc tupdesc; ++rt_index; /* * Only normal relations can have virtual generated columns. */ if (rte->rtekind != RTE_RELATION) continue; rel = table_open(rte->relid, NoLock); tupdesc = RelationGetDescr(rel); if (tupdesc->constr && tupdesc->constr->has_generated_virtual) { List *tlist = NIL; pullup_replace_vars_context rvcontext; for (int i = 0; i < tupdesc->natts; i++) { Form_pg_attribute attr = TupleDescAttr(tupdesc, i); TargetEntry *tle; if (attr->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL) { Node *defexpr; defexpr = build_generation_expression(rel, i + 1); ChangeVarNodes(defexpr, 1, rt_index, 0); tle = makeTargetEntry((Expr *) defexpr, i + 1, 0, false); tlist = lappend(tlist, tle); } else { Var *var; var = makeVar(rt_index, i + 1, attr->atttypid, attr->atttypmod, attr->attcollation, 0); tle = makeTargetEntry((Expr *) var, i + 1, 0, false); tlist = lappend(tlist, tle); } } Assert(list_length(tlist) > 0); Assert(!rte->lateral); /* * The relation's targetlist items are now in the appropriate form * to insert into the query, except that we may need to wrap them * in PlaceHolderVars. Set up required context data for * pullup_replace_vars. */ rvcontext.root = root; rvcontext.targetlist = tlist; rvcontext.target_rte = rte; rvcontext.result_relation = parse->resultRelation; /* won't need these values */ rvcontext.relids = NULL; rvcontext.nullinfo = NULL; /* pass NULL for outer_hasSubLinks */ rvcontext.outer_hasSubLinks = NULL; rvcontext.varno = rt_index; /* this flag will be set below, if needed */ rvcontext.wrap_option = REPLACE_WRAP_NONE; /* initialize cache array with indexes 0 .. length(tlist) */ rvcontext.rv_cache = palloc0((list_length(tlist) + 1) * sizeof(Node *)); /* * If the query uses grouping sets, we need a PlaceHolderVar for * each expression of the relation's targetlist items. (See * comments in pull_up_simple_subquery().) */ if (parse->groupingSets) rvcontext.wrap_option = REPLACE_WRAP_ALL; /* * Apply pullup variable replacement throughout the query tree. */ parse = (Query *) pullup_replace_vars((Node *) parse, &rvcontext); } table_close(rel, NoLock); } return parse; } /* * 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". */ void pull_up_subqueries(PlannerInfo *root) { /* Top level of jointree must always be a FromExpr */ Assert(IsA(root->parse->jointree, FromExpr)); /* Recursion starts with no containing join nor appendrel */ root->parse->jointree = (FromExpr *) pull_up_subqueries_recurse(root, (Node *) root->parse->jointree, NULL, NULL); /* We should still have a FromExpr */ Assert(IsA(root->parse->jointree, FromExpr)); } /* * pull_up_subqueries_recurse * Recursive guts of pull_up_subqueries. * * This recursively processes the jointree and returns a modified jointree. * * If this jointree node is within either side of an outer join, then * lowest_outer_join references the lowest such JoinExpr node; otherwise * it is NULL. We use this to constrain the effects of LATERAL subqueries. * * If we are looking at a member subquery of an append relation, * containing_appendrel describes that relation; else it is NULL. * This forces use of the PlaceHolderVar mechanism for all non-Var targetlist * items, and puts some additional restrictions on what can be pulled up. * * 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 to maintain * validity of the jointree structure while recursing, in the following sense: * whenever we recurse, all qual expressions in the tree must be reachable * from the top level, in case the recursive call needs to modify them. * * Notice also that we can't turn pullup_replace_vars loose on the whole * jointree, because it'd return a mutated copy of the tree; we have to * invoke it just on the quals, instead. This behavior is what makes it * reasonable to pass lowest_outer_join as a pointer rather than some * more-indirect way of identifying the lowest OJ. Likewise, we don't * replace append_rel_list members but only their substructure, so the * containing_appendrel reference is safe to use. */ static Node * pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode, JoinExpr *lowest_outer_join, AppendRelInfo *containing_appendrel) { /* Since this function recurses, it could be driven to stack overflow. */ check_stack_depth(); /* Also, since it's a bit expensive, let's check for query cancel. */ CHECK_FOR_INTERRUPTS(); Assert(jtnode != 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 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(root, rte->subquery, rte, lowest_outer_join) && (containing_appendrel == NULL || is_safe_append_member(rte->subquery))) return pull_up_simple_subquery(root, jtnode, rte, lowest_outer_join, containing_appendrel); /* * Alternatively, is it a simple UNION ALL subquery? If so, flatten * into an "append relation". * * It's 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); /* * Or perhaps it's a simple VALUES RTE? * * We don't allow VALUES pullup below an outer join nor into an * appendrel (such cases are impossible anyway at the moment). */ if (rte->rtekind == RTE_VALUES && lowest_outer_join == NULL && containing_appendrel == NULL && is_simple_values(root, rte)) return pull_up_simple_values(root, jtnode, rte); /* * Or perhaps it's a FUNCTION RTE that we could inline? */ if (rte->rtekind == RTE_FUNCTION) return pull_up_constant_function(root, jtnode, rte, containing_appendrel); /* Otherwise, do nothing at this node. */ } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; Assert(containing_appendrel == NULL); /* Recursively transform all the child nodes */ foreach(l, f->fromlist) { lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l), lowest_outer_join, NULL); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; Assert(containing_appendrel == NULL); /* Recurse, being careful to tell myself when inside outer join */ switch (j->jointype) { case JOIN_INNER: j->larg = pull_up_subqueries_recurse(root, j->larg, lowest_outer_join, NULL); j->rarg = pull_up_subqueries_recurse(root, j->rarg, lowest_outer_join, NULL); break; case JOIN_LEFT: case JOIN_SEMI: case JOIN_ANTI: j->larg = pull_up_subqueries_recurse(root, j->larg, j, NULL); j->rarg = pull_up_subqueries_recurse(root, j->rarg, j, NULL); break; case JOIN_FULL: j->larg = pull_up_subqueries_recurse(root, j->larg, j, NULL); j->rarg = pull_up_subqueries_recurse(root, j->rarg, j, NULL); break; case JOIN_RIGHT: j->larg = pull_up_subqueries_recurse(root, j->larg, j, NULL); j->rarg = pull_up_subqueries_recurse(root, j->rarg, j, NULL); 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. * * rte is the RangeTblEntry referenced by jtnode. Remaining parameters are * as for pull_up_subqueries_recurse. */ static Node * pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, JoinExpr *lowest_outer_join, AppendRelInfo *containing_appendrel) { Query *parse = root->parse; int varno = ((RangeTblRef *) jtnode)->rtindex; Query *subquery; PlannerInfo *subroot; int rtoffset; pullup_replace_vars_context rvcontext; ListCell *lc; /* * Make a modifiable copy of the subquery to hack on, so that the RTE will * be left unchanged in case we decide below that we can't pull it up * after all. */ 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->parent_root = root->parent_root; subroot->plan_params = NIL; subroot->outer_params = NULL; subroot->planner_cxt = CurrentMemoryContext; subroot->init_plans = NIL; subroot->cte_plan_ids = NIL; subroot->multiexpr_params = NIL; subroot->join_domains = NIL; subroot->eq_classes = NIL; subroot->ec_merging_done = false; subroot->last_rinfo_serial = 0; subroot->all_result_relids = NULL; subroot->leaf_result_relids = NULL; subroot->append_rel_list = NIL; subroot->row_identity_vars = NIL; subroot->rowMarks = NIL; memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels)); memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets)); subroot->processed_groupClause = NIL; subroot->processed_distinctClause = NIL; subroot->processed_tlist = NIL; subroot->update_colnos = NIL; subroot->grouping_map = NULL; subroot->minmax_aggs = NIL; subroot->qual_security_level = 0; subroot->placeholdersFrozen = false; subroot->hasRecursion = false; subroot->wt_param_id = -1; subroot->non_recursive_path = NULL; /* We don't currently need a top JoinDomain for the subroot */ /* No CTEs to worry about */ Assert(subquery->cteList == NIL); /* * If the FROM clause is empty, replace it with a dummy RTE_RESULT RTE, so * that we don't need so many special cases to deal with that situation. */ replace_empty_jointree(subquery); /* * Pull up any SubLinks within the subquery's quals, so that we don't * leave unoptimized SubLinks behind. */ if (subquery->hasSubLinks) pull_up_sublinks(subroot); /* * Similarly, preprocess its function RTEs to inline any set-returning * functions in its rangetable. */ preprocess_function_rtes(subroot); /* * Scan the rangetable for relations with virtual generated columns, and * replace all Var nodes in the query that reference these columns with * the generation expressions. */ subquery = subroot->parse = expand_virtual_generated_columns(subroot); /* * Recursively pull up the subquery's subqueries, so that * pull_up_subqueries' processing is complete for its jointree and * rangetable. * * Note: it's okay that the subquery's recursion starts with NULL for * containing-join info, 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 needn't pass down appendrel state. */ pull_up_subqueries(subroot); /* * 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_recurse. */ if (is_simple_subquery(root, subquery, rte, lowest_outer_join) && (containing_appendrel == NULL || 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; } /* * We must flatten any join alias Vars in the subquery's targetlist, * because pulling up the subquery's subqueries might have changed their * expansions into arbitrary expressions, which could affect * pullup_replace_vars' decisions about whether PlaceHolderVar wrappers * are needed for tlist entries. (Likely it'd be better to do * flatten_join_alias_vars on the whole query tree at some earlier stage, * maybe even in the rewriter; but for now let's just fix this case here.) */ subquery->targetList = (List *) flatten_join_alias_vars(subroot, subroot->parse, (Node *) subquery->targetList); /* * Adjust level-0 varnos in subquery so that we can append its rangetable * to upper query's. We have to fix the subquery's append_rel_list as * well. */ rtoffset = list_length(parse->rtable); OffsetVarNodes((Node *) subquery, 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->append_rel_list, -1, 1); /* * The subquery's targetlist items are now in the appropriate form to * insert into the top query, except that we may need to wrap them in * PlaceHolderVars. Set up required context data for pullup_replace_vars. * (Note that we should include the subquery's inner joins in relids, * since it may include join alias vars referencing them.) */ rvcontext.root = root; rvcontext.targetlist = subquery->targetList; rvcontext.target_rte = rte; rvcontext.result_relation = 0; if (rte->lateral) { rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree, true, true); rvcontext.nullinfo = get_nullingrels(parse); } else /* won't need these values */ { rvcontext.relids = NULL; rvcontext.nullinfo = NULL; } rvcontext.outer_hasSubLinks = &parse->hasSubLinks; rvcontext.varno = varno; /* this flag will be set below, if needed */ rvcontext.wrap_option = REPLACE_WRAP_NONE; /* initialize cache array with indexes 0 .. length(tlist) */ rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) * sizeof(Node *)); /* * If the parent query uses grouping sets, we need a PlaceHolderVar for * each expression of the subquery's targetlist items. This ensures that * expressions retain their separate identity so that they will match * grouping set columns when appropriate. (It'd be sufficient to wrap * values used in grouping set columns, and do so only in non-aggregated * portions of the tlist and havingQual, but that would require a lot of * infrastructure that pullup_replace_vars hasn't currently got.) */ if (parse->groupingSets) rvcontext.wrap_option = REPLACE_WRAP_ALL; /* * 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. */ perform_pullup_replace_vars(root, &rvcontext, containing_appendrel); /* * If the subquery had a LATERAL marker, propagate that to any of its * child RTEs that could possibly now contain lateral cross-references. * The children might or might not contain any actual lateral * cross-references, but we have to mark the pulled-up child RTEs so that * later planner stages will check for such. */ if (rte->lateral) { foreach(lc, subquery->rtable) { RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(lc); switch (child_rte->rtekind) { case RTE_RELATION: if (child_rte->tablesample) child_rte->lateral = true; break; case RTE_SUBQUERY: case RTE_FUNCTION: case RTE_VALUES: case RTE_TABLEFUNC: child_rte->lateral = true; break; case RTE_JOIN: case RTE_CTE: case RTE_NAMEDTUPLESTORE: case RTE_RESULT: case RTE_GROUP: /* these can't contain any lateral references */ break; } } } /* * Now append the adjusted rtable entries and their perminfos to upper * query. (We hold off until after fixing the upper rtable entries; no * point in running that code on the subquery ones too.) */ CombineRangeTables(&parse->rtable, &parse->rteperminfos, subquery->rtable, subquery->rteperminfos); /* * 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 PlaceHolderVar nodes in the * parent query. (This could perhaps be done by pullup_replace_vars(), * but it seems cleaner to use two passes.) Note in particular that any * PlaceHolderVar nodes just created by pullup_replace_vars() will be * adjusted, so having created them with the subquery's varno is correct. * * Likewise, relids appearing in AppendRelInfo nodes have to be fixed. We * already checked that this won't require introducing multiple subrelids * into the single-slot AppendRelInfo structs. */ if (root->glob->lastPHId != 0 || root->append_rel_list) { Relids subrelids; subrelids = get_relids_in_jointree((Node *) subquery->jointree, true, false); if (root->glob->lastPHId != 0) substitute_phv_relids((Node *) parse, varno, subrelids); fix_append_rel_relids(root, varno, subrelids); } /* * And now add subquery's AppendRelInfos to our 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. placeholder_list likewise. */ Assert(root->join_info_list == NIL); Assert(subroot->join_info_list == NIL); Assert(root->placeholder_list == NIL); Assert(subroot->placeholder_list == NIL); /* * We no longer need the RTE's copy of the subquery's query tree. Getting * rid of it saves nothing in particular so far as this level of query is * concerned; but if this query level is in turn pulled up into a parent, * we'd waste cycles copying the now-unused query tree. */ rte->subquery = NULL; /* * Miscellaneous housekeeping. * * Although replace_rte_variables() faithfully updated parse->hasSubLinks * if it copied any SubLinks out of the subquery's targetlist, we still * could have SubLinks added to the query in the expressions of FUNCTION * and VALUES RTEs copied up from the subquery. So it's necessary to copy * subquery->hasSubLinks anyway. Perhaps this can be improved someday. */ parse->hasSubLinks |= subquery->hasSubLinks; /* If subquery had any RLS conditions, now main query does too */ parse->hasRowSecurity |= subquery->hasRowSecurity; /* * subquery won't be pulled up if it hasAggs, hasWindowFuncs, or * hasTargetSRFs, so no work needed on those flags */ /* * Return the adjusted subquery jointree to replace the RangeTblRef entry * in parent's jointree; or, if the FromExpr is degenerate, just return * its single member. */ Assert(IsA(subquery->jointree, FromExpr)); Assert(subquery->jointree->fromlist != NIL); if (subquery->jointree->quals == NULL && list_length(subquery->jointree->fromlist) == 1) return (Node *) linitial(subquery->jointree->fromlist); 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; int rtoffset = list_length(root->parse->rtable); List *rtable; /* * Make a modifiable copy of the subquery's rtable, so we can adjust * upper-level Vars in it. There are no such Vars in the setOperations * tree proper, so fixing the rtable should be sufficient. */ rtable = copyObject(subquery->rtable); /* * 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 the UNION leaf queries can't cross-reference each other. */ IncrementVarSublevelsUp_rtable(rtable, -1, 1); /* * If the UNION ALL subquery had a LATERAL marker, propagate that to all * its children. The individual children might or might not contain any * actual lateral cross-references, but we have to mark the pulled-up * child RTEs so that later planner stages will check for such. */ if (rte->lateral) { ListCell *rt; foreach(rt, rtable) { RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(rt); Assert(child_rte->rtekind == RTE_SUBQUERY); child_rte->lateral = true; } } /* * Append child RTEs (and their perminfos) to parent rtable. */ CombineRangeTables(&root->parse->rtable, &root->parse->rteperminfos, rtable, subquery->rteperminfos); /* * Recursively scan the subquery's setOperations tree and add * AppendRelInfo nodes for leaf subqueries to the parent's * append_rel_list. Also apply pull_up_subqueries to the leaf subqueries. */ Assert(subquery->setOperations); pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery, rtoffset); /* * 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 * * Build an AppendRelInfo for each leaf query in the setop tree, and then * apply pull_up_subqueries to the leaf query. * * Note that setOpQuery is the Query containing the setOp node, whose tlist * contains references to all the setop output columns. When called from * pull_up_simple_union_all, this is *not* the same as root->parse, which is * the parent Query we are pulling up into. * * parentRTindex is the appendrel parent's index in root->parse->rtable. * * The child RTEs have already been copied to the parent. childRToffset * tells us where in the parent's range table they were copied. When called * from flatten_simple_union_all, childRToffset is 0 since the child RTEs * were already in root->parse->rtable and no RT index adjustment is needed. */ static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex, Query *setOpQuery, int childRToffset) { if (IsA(setOp, RangeTblRef)) { RangeTblRef *rtr = (RangeTblRef *) setOp; int childRTindex; AppendRelInfo *appinfo; /* * Calculate the index in the parent's range table */ childRTindex = childRToffset + rtr->rtindex; /* * 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_list(setOpQuery, childRTindex, appinfo); 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; * indeed, that's the only part of the upper query where Vars * referencing childRTindex can exist at this point.) * * Note that we can pass NULL for containing-join info even if we're * actually under an outer join, because the child's expressions * aren't going to propagate up to the join. Also, we ignore the * possibility that pull_up_subqueries_recurse() returns a different * jointree node than what we pass it; if it does, the important thing * is that it replaced the child relid in the AppendRelInfo node. */ rtr = makeNode(RangeTblRef); rtr->rtindex = childRTindex; (void) pull_up_subqueries_recurse(root, (Node *) rtr, NULL, appinfo); } else if (IsA(setOp, SetOperationStmt)) { SetOperationStmt *op = (SetOperationStmt *) setOp; /* Recurse to reach leaf queries */ pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery, childRToffset); pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery, childRToffset); } else { elog(ERROR, "unrecognized node type: %d", (int) nodeTag(setOp)); } } /* * make_setop_translation_list * Build the list of translations from parent Vars to child Vars for * a UNION ALL member. (At this point it's just a simple list of * referencing Vars, but if we succeed in pulling up the member * subquery, the Vars will get replaced by pulled-up expressions.) * Also create the rather trivial reverse-translation array. */ static void make_setop_translation_list(Query *query, int newvarno, AppendRelInfo *appinfo) { List *vars = NIL; AttrNumber *pcolnos; ListCell *l; /* Initialize reverse-translation array with all entries zero */ /* (entries for resjunk columns will stay that way) */ appinfo->num_child_cols = list_length(query->targetList); appinfo->parent_colnos = pcolnos = (AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber)); foreach(l, query->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(l); if (tle->resjunk) continue; vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle)); pcolnos[tle->resno - 1] = tle->resno; } appinfo->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. * * rte is the RTE_SUBQUERY RangeTblEntry that contained the subquery. * (Note subquery is not necessarily equal to rte->subquery; it could be a * processed copy of that.) * lowest_outer_join is the lowest outer join above the subquery, or NULL. */ static bool is_simple_subquery(PlannerInfo *root, Query *subquery, RangeTblEntry *rte, JoinExpr *lowest_outer_join) { /* * Let's just make sure it's a valid subselect ... */ if (!IsA(subquery, Query) || subquery->commandType != CMD_SELECT) 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, SRFs, * sorting, limiting, or WITH. (XXX WITH could possibly be allowed later) * * We also don't pull up a subquery that has explicit FOR UPDATE/SHARE * clauses, because pullup would cause the locking to occur semantically * higher than it should. Implicit FOR UPDATE/SHARE is okay because in * that case the locking was originally declared in the upper query * anyway. */ if (subquery->hasAggs || subquery->hasWindowFuncs || subquery->hasTargetSRFs || subquery->groupClause || subquery->groupingSets || subquery->havingQual || subquery->sortClause || subquery->distinctClause || subquery->limitOffset || subquery->limitCount || subquery->hasForUpdate || subquery->cteList) return false; /* * Don't pull up if the RTE represents a security-barrier view; we * couldn't prevent information leakage once the RTE's Vars are scattered * about in the upper query. */ if (rte->security_barrier) return false; /* * If the subquery is LATERAL, check for pullup restrictions from that. */ if (rte->lateral) { bool restricted; Relids safe_upper_varnos; /* * The subquery's WHERE and JOIN/ON quals mustn't contain any lateral * references to rels outside a higher outer join (including the case * where the outer join is within the subquery itself). In such a * case, pulling up would result in a situation where we need to * postpone quals from below an outer join to above it, which is * probably completely wrong and in any case is a complication that * doesn't seem worth addressing at the moment. */ if (lowest_outer_join != NULL) { restricted = true; safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join, true, true); } else { restricted = false; safe_upper_varnos = NULL; /* doesn't matter */ } if (jointree_contains_lateral_outer_refs(root, (Node *) subquery->jointree, restricted, safe_upper_varnos)) return false; /* * If there's an outer join above the LATERAL subquery, also disallow * pullup if the subquery's targetlist has any references to rels * outside the outer join, since these might get pulled into quals * above the subquery (but in or below the outer join) and then lead * to qual-postponement issues similar to the case checked for above. * (We wouldn't need to prevent pullup if no such references appear in * outer-query quals, but we don't have enough info here to check * that. Also, maybe this restriction could be removed if we forced * such refs to be wrapped in PlaceHolderVars, even when they're below * the nearest outer join? But it's a pretty hokey usage, so not * clear this is worth sweating over.) * * If you change this, see also the comments about lateral references * in pullup_replace_vars_callback(). */ if (lowest_outer_join != NULL) { Relids lvarnos = pull_varnos_of_level(root, (Node *) subquery->targetList, 1); if (!bms_is_subset(lvarnos, safe_upper_varnos)) 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. (Note: the PlaceHolderVar mechanism * doesn't quite guarantee single evaluation; else we could pull up anyway * and just wrap such items in PlaceHolderVars ...) */ if (contain_volatile_functions((Node *) subquery->targetList)) return false; return true; } /* * pull_up_simple_values * Pull up a single simple VALUES RTE. * * jtnode is a RangeTblRef that has been identified as a simple VALUES RTE * by pull_up_subqueries. We always return a RangeTblRef representing a * RESULT RTE to replace it (all failure cases should have been detected by * is_simple_values()). Actually, what we return is just jtnode, because * we replace the VALUES RTE in the rangetable with the RESULT RTE. * * rte is the RangeTblEntry referenced by jtnode. Because of the limited * possible usage of VALUES RTEs, we do not need the remaining parameters * of pull_up_subqueries_recurse. */ static Node * pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte) { Query *parse = root->parse; int varno = ((RangeTblRef *) jtnode)->rtindex; List *values_list; List *tlist; AttrNumber attrno; pullup_replace_vars_context rvcontext; ListCell *lc; Assert(rte->rtekind == RTE_VALUES); Assert(list_length(rte->values_lists) == 1); /* * Need a modifiable copy of the VALUES list to hack on, just in case it's * multiply referenced. */ values_list = copyObject(linitial(rte->values_lists)); /* * The VALUES RTE can't contain any Vars of level zero, let alone any that * are join aliases, so no need to flatten join alias Vars. */ Assert(!contain_vars_of_level((Node *) values_list, 0)); /* * Set up required context data for pullup_replace_vars. In particular, * we have to make the VALUES list look like a subquery targetlist. */ tlist = NIL; attrno = 1; foreach(lc, values_list) { tlist = lappend(tlist, makeTargetEntry((Expr *) lfirst(lc), attrno, NULL, false)); attrno++; } rvcontext.root = root; rvcontext.targetlist = tlist; rvcontext.target_rte = rte; rvcontext.result_relation = 0; rvcontext.relids = NULL; /* can't be any lateral references here */ rvcontext.nullinfo = NULL; rvcontext.outer_hasSubLinks = &parse->hasSubLinks; rvcontext.varno = varno; rvcontext.wrap_option = REPLACE_WRAP_NONE; /* initialize cache array with indexes 0 .. length(tlist) */ rvcontext.rv_cache = palloc0((list_length(tlist) + 1) * sizeof(Node *)); /* * Replace all of the top query's references to the RTE's outputs with * copies of the adjusted VALUES expressions, being careful not to replace * any of the jointree structure. We can assume there's no outer joins or * appendrels in the dummy Query that surrounds a VALUES RTE. */ perform_pullup_replace_vars(root, &rvcontext, NULL); /* * There should be no appendrels to fix, nor any outer joins and hence no * PlaceHolderVars. */ Assert(root->append_rel_list == NIL); Assert(root->join_info_list == NIL); Assert(root->placeholder_list == NIL); /* * Replace the VALUES RTE with a RESULT RTE. The VALUES RTE is the only * rtable entry in the current query level, so this is easy. */ Assert(list_length(parse->rtable) == 1); /* Create suitable RTE */ rte = makeNode(RangeTblEntry); rte->rtekind = RTE_RESULT; rte->eref = makeAlias("*RESULT*", NIL); /* Replace rangetable */ parse->rtable = list_make1(rte); /* We could manufacture a new RangeTblRef, but the one we have is fine */ Assert(varno == 1); return jtnode; } /* * is_simple_values * Check a VALUES RTE in the range table to see if it's simple enough * to pull up into the parent query. * * rte is the RTE_VALUES RangeTblEntry to check. */ static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte) { Assert(rte->rtekind == RTE_VALUES); /* * There must be exactly one VALUES list, else it's not semantically * correct to replace the VALUES RTE with a RESULT RTE, nor would we have * a unique set of expressions to substitute into the parent query. */ if (list_length(rte->values_lists) != 1) return false; /* * Because VALUES can't appear under an outer join (or at least, we won't * try to pull it up if it does), we need not worry about LATERAL, nor * about validity of PHVs for the VALUES' outputs. */ /* * Don't pull up a VALUES that contains any set-returning or volatile * functions. The considerations here are basically identical to the * restrictions on a pull-able subquery's targetlist. */ if (expression_returns_set((Node *) rte->values_lists) || contain_volatile_functions((Node *) rte->values_lists)) return false; /* * Do not pull up a VALUES that's not the only RTE in its parent query. * This is actually the only case that the parser will generate at the * moment, and assuming this is true greatly simplifies * pull_up_simple_values(). */ if (list_length(root->parse->rtable) != 1 || rte != (RangeTblEntry *) linitial(root->parse->rtable)) return false; return true; } /* * pull_up_constant_function * Pull up an RTE_FUNCTION expression that was simplified to a constant. * * jtnode is a RangeTblRef that has been identified as a FUNCTION RTE by * pull_up_subqueries. If its expression is just a Const, hoist that value * up into the parent query, and replace the RTE_FUNCTION with RTE_RESULT. * * In principle we could pull up any immutable expression, but we don't. * That might result in multiple evaluations of the expression, which could * be costly if it's not just a Const. Also, the main value of this is * to let the constant participate in further const-folding, and of course * that won't happen for a non-Const. * * The pulled-up value might need to be wrapped in a PlaceHolderVar if the * RTE is below an outer join or is part of an appendrel; the extra * parameters show whether that's needed. */ static Node * pull_up_constant_function(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte, AppendRelInfo *containing_appendrel) { Query *parse = root->parse; RangeTblFunction *rtf; TypeFuncClass functypclass; Oid funcrettype; TupleDesc tupdesc; pullup_replace_vars_context rvcontext; /* Fail if the RTE has ORDINALITY - we don't implement that here. */ if (rte->funcordinality) return jtnode; /* Fail if RTE isn't a single, simple Const expr */ if (list_length(rte->functions) != 1) return jtnode; rtf = linitial_node(RangeTblFunction, rte->functions); if (!IsA(rtf->funcexpr, Const)) return jtnode; /* * If the function's result is not a scalar, we punt. In principle we * could break the composite constant value apart into per-column * constants, but for now it seems not worth the work. */ if (rtf->funccolcount != 1) return jtnode; /* definitely composite */ /* If it has a coldeflist, it certainly returns RECORD */ if (rtf->funccolnames != NIL) return jtnode; /* must be a one-column RECORD type */ functypclass = get_expr_result_type(rtf->funcexpr, &funcrettype, &tupdesc); if (functypclass != TYPEFUNC_SCALAR) return jtnode; /* must be a one-column composite type */ /* Create context for applying pullup_replace_vars */ rvcontext.root = root; rvcontext.targetlist = list_make1(makeTargetEntry((Expr *) rtf->funcexpr, 1, /* resno */ NULL, /* resname */ false)); /* resjunk */ rvcontext.target_rte = rte; rvcontext.result_relation = 0; /* * Since this function was reduced to a Const, it doesn't contain any * lateral references, even if it's marked as LATERAL. This means we * don't need to fill relids or nullinfo. */ rvcontext.relids = NULL; rvcontext.nullinfo = NULL; rvcontext.outer_hasSubLinks = &parse->hasSubLinks; rvcontext.varno = ((RangeTblRef *) jtnode)->rtindex; /* this flag will be set below, if needed */ rvcontext.wrap_option = REPLACE_WRAP_NONE; /* initialize cache array with indexes 0 .. length(tlist) */ rvcontext.rv_cache = palloc0((list_length(rvcontext.targetlist) + 1) * sizeof(Node *)); /* * If the parent query uses grouping sets, we need a PlaceHolderVar for * each expression of the subquery's targetlist items. (See comments in * pull_up_simple_subquery().) */ if (parse->groupingSets) rvcontext.wrap_option = REPLACE_WRAP_ALL; /* * Replace all of the top query's references to the RTE's output with * copies of the funcexpr, being careful not to replace any of the * jointree structure. */ perform_pullup_replace_vars(root, &rvcontext, containing_appendrel); /* * We don't need to bother with changing PlaceHolderVars in the parent * query. Their references to the RT index are still good for now, and * will get removed later if we're able to drop the RTE_RESULT. */ /* * Convert the RTE to be RTE_RESULT type, signifying that we don't need to * scan it anymore, and zero out RTE_FUNCTION-specific fields. Also make * sure the RTE is not marked LATERAL, since elsewhere we don't expect * RTE_RESULTs to be LATERAL. */ rte->rtekind = RTE_RESULT; rte->functions = NIL; rte->lateral = false; /* * We can reuse the RangeTblRef node. */ return jtnode; } /* * 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) elog(ERROR, "subquery is bogus"); /* Is it a set-operation query at all? */ topop = castNode(SetOperationStmt, subquery->setOperations); if (!topop) return false; /* Can't handle ORDER BY, LIMIT/OFFSET, locking, or WITH */ if (subquery->sortClause || subquery->limitOffset || subquery->limitCount || subquery->rowMarks || subquery->cteList) 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) { /* Since this function recurses, it could be driven to stack overflow. */ check_stack_depth(); 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 or collations 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 */ } } /* * 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; /* * 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, if the * child's jointree is completely empty, we can pull up because * pull_up_simple_subquery will insert a single RTE_RESULT RTE instead. * * 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; Assert(IsA(jtnode, FromExpr)); /* Check the completely-empty case */ if (jtnode->fromlist == NIL && jtnode->quals == NULL) return true; /* Check the more general case */ 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; return true; } /* * jointree_contains_lateral_outer_refs * Check for disallowed lateral references in a jointree's quals * * If restricted is false, all level-1 Vars are allowed (but we still must * search the jointree, since it might contain outer joins below which there * will be restrictions). If restricted is true, return true when any qual * in the jointree contains level-1 Vars coming from outside the rels listed * in safe_upper_varnos. */ static bool jointree_contains_lateral_outer_refs(PlannerInfo *root, Node *jtnode, bool restricted, Relids safe_upper_varnos) { if (jtnode == NULL) return false; if (IsA(jtnode, RangeTblRef)) return false; else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; /* First, recurse to check child joins */ foreach(l, f->fromlist) { if (jointree_contains_lateral_outer_refs(root, lfirst(l), restricted, safe_upper_varnos)) return true; } /* Then check the top-level quals */ if (restricted && !bms_is_subset(pull_varnos_of_level(root, f->quals, 1), safe_upper_varnos)) return true; } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; /* * If this is an outer join, we mustn't allow any upper lateral * references in or below it. */ if (j->jointype != JOIN_INNER) { restricted = true; safe_upper_varnos = NULL; } /* Check the child joins */ if (jointree_contains_lateral_outer_refs(root, j->larg, restricted, safe_upper_varnos)) return true; if (jointree_contains_lateral_outer_refs(root, j->rarg, restricted, safe_upper_varnos)) return true; /* Check the JOIN's qual clauses */ if (restricted && !bms_is_subset(pull_varnos_of_level(root, j->quals, 1), safe_upper_varnos)) return true; } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return false; } /* * Perform pullup_replace_vars everyplace it's needed in the query tree. * * Caller has already filled *rvcontext with data describing what to * substitute for Vars referencing the target subquery. In addition * we need the identity of the containing appendrel if any. */ static void perform_pullup_replace_vars(PlannerInfo *root, pullup_replace_vars_context *rvcontext, AppendRelInfo *containing_appendrel) { Query *parse = root->parse; ListCell *lc; /* * If we are considering an appendrel child subquery (that is, a UNION ALL * member query that we're pulling up), then the only part of the upper * query that could reference the child yet is the translated_vars list of * the associated AppendRelInfo. Furthermore, we do not want to force use * of PHVs in the AppendRelInfo --- there isn't any outer join between. */ if (containing_appendrel) { ReplaceWrapOption save_wrap_option = rvcontext->wrap_option; rvcontext->wrap_option = REPLACE_WRAP_NONE; containing_appendrel->translated_vars = (List *) pullup_replace_vars((Node *) containing_appendrel->translated_vars, rvcontext); rvcontext->wrap_option = save_wrap_option; return; } /* * 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.) We have to use PHVs in the targetList, * returningList, and havingQual, since those are certainly above any * outer join. replace_vars_in_jointree tracks its location in the * jointree and uses PHVs or not appropriately. */ parse->targetList = (List *) pullup_replace_vars((Node *) parse->targetList, rvcontext); parse->returningList = (List *) pullup_replace_vars((Node *) parse->returningList, rvcontext); if (parse->onConflict) { parse->onConflict->onConflictSet = (List *) pullup_replace_vars((Node *) parse->onConflict->onConflictSet, rvcontext); parse->onConflict->onConflictWhere = pullup_replace_vars(parse->onConflict->onConflictWhere, rvcontext); /* * We assume ON CONFLICT's arbiterElems, arbiterWhere, exclRelTlist * can't contain any references to a subquery. */ } if (parse->mergeActionList) { foreach(lc, parse->mergeActionList) { MergeAction *action = lfirst(lc); action->qual = pullup_replace_vars(action->qual, rvcontext); action->targetList = (List *) pullup_replace_vars((Node *) action->targetList, rvcontext); } } parse->mergeJoinCondition = pullup_replace_vars(parse->mergeJoinCondition, rvcontext); replace_vars_in_jointree((Node *) parse->jointree, rvcontext); Assert(parse->setOperations == NULL); parse->havingQual = pullup_replace_vars(parse->havingQual, rvcontext); /* * Replace references in the translated_vars lists of appendrels. */ foreach(lc, root->append_rel_list) { AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc); appinfo->translated_vars = (List *) pullup_replace_vars((Node *) appinfo->translated_vars, rvcontext); } /* * Replace references in the joinaliasvars lists of join RTEs and the * groupexprs list of group RTE. */ foreach(lc, parse->rtable) { RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc); if (otherrte->rtekind == RTE_JOIN) otherrte->joinaliasvars = (List *) pullup_replace_vars((Node *) otherrte->joinaliasvars, rvcontext); else if (otherrte->rtekind == RTE_GROUP) otherrte->groupexprs = (List *) pullup_replace_vars((Node *) otherrte->groupexprs, rvcontext); } } /* * Helper routine for perform_pullup_replace_vars: do pullup_replace_vars on * every expression in the jointree, without changing the jointree structure * itself. Ugly, but there's no other way... */ static void replace_vars_in_jointree(Node *jtnode, pullup_replace_vars_context *context) { if (jtnode == NULL) return; if (IsA(jtnode, RangeTblRef)) { /* * If the RangeTblRef refers to a LATERAL subquery (that isn't the * same subquery we're pulling up), it might contain references to the * target subquery, which we must replace. We drive this from the * jointree scan, rather than a scan of the rtable, so that we can * avoid processing no-longer-referenced RTEs. */ int varno = ((RangeTblRef *) jtnode)->rtindex; if (varno != context->varno) /* ignore target subquery itself */ { RangeTblEntry *rte = rt_fetch(varno, context->root->parse->rtable); Assert(rte != context->target_rte); if (rte->lateral) { switch (rte->rtekind) { case RTE_RELATION: /* shouldn't be marked LATERAL unless tablesample */ Assert(rte->tablesample); rte->tablesample = (TableSampleClause *) pullup_replace_vars((Node *) rte->tablesample, context); break; case RTE_SUBQUERY: rte->subquery = pullup_replace_vars_subquery(rte->subquery, context); break; case RTE_FUNCTION: rte->functions = (List *) pullup_replace_vars((Node *) rte->functions, context); break; case RTE_TABLEFUNC: rte->tablefunc = (TableFunc *) pullup_replace_vars((Node *) rte->tablefunc, context); break; case RTE_VALUES: rte->values_lists = (List *) pullup_replace_vars((Node *) rte->values_lists, context); break; case RTE_JOIN: case RTE_CTE: case RTE_NAMEDTUPLESTORE: case RTE_RESULT: case RTE_GROUP: /* these shouldn't be marked LATERAL */ Assert(false); break; } } } } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) replace_vars_in_jointree(lfirst(l), context); f->quals = pullup_replace_vars(f->quals, context); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; ReplaceWrapOption save_wrap_option = context->wrap_option; replace_vars_in_jointree(j->larg, context); replace_vars_in_jointree(j->rarg, context); /* * Use PHVs within the join quals of a full join for variable-free * expressions. Otherwise, we cannot identify which side of the join * a pulled-up variable-free expression came from, which can lead to * failure to make a plan at all because none of the quals appear to * be mergeable or hashable conditions. */ if (j->jointype == JOIN_FULL) context->wrap_option = REPLACE_WRAP_VARFREE; j->quals = pullup_replace_vars(j->quals, context); context->wrap_option = save_wrap_option; } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /* * Apply pullup variable replacement throughout an expression tree * * Returns a modified copy of the tree, so this can't be used where we * need to do in-place replacement. */ static Node * pullup_replace_vars(Node *expr, pullup_replace_vars_context *context) { return replace_rte_variables(expr, context->varno, 0, pullup_replace_vars_callback, context, context->outer_hasSubLinks); } static Node * pullup_replace_vars_callback(Var *var, replace_rte_variables_context *context) { pullup_replace_vars_context *rcon = (pullup_replace_vars_context *) context->callback_arg; int varattno = var->varattno; bool need_phv; Node *newnode; /* System columns are not replaced. */ if (varattno < InvalidAttrNumber) return (Node *) copyObject(var); /* * We need a PlaceHolderVar if the Var-to-be-replaced has nonempty * varnullingrels (unless we find below that the replacement expression is * a Var or PlaceHolderVar that we can just add the nullingrels to). We * also need one if the caller has instructed us that certain expression * replacements need to be wrapped for identification purposes. */ need_phv = (var->varnullingrels != NULL) || (rcon->wrap_option != REPLACE_WRAP_NONE); /* * If PlaceHolderVars are needed, we cache the modified expressions in * rcon->rv_cache[]. This is not in hopes of any material speed gain * within this function, but to avoid generating identical PHVs with * different IDs. That would result in duplicate evaluations at runtime, * and possibly prevent optimizations that rely on recognizing different * references to the same subquery output as being equal(). So it's worth * a bit of extra effort to avoid it. * * The cached items have phlevelsup = 0 and phnullingrels = NULL; we'll * copy them and adjust those values for this reference site below. */ if (need_phv && varattno >= InvalidAttrNumber && varattno <= list_length(rcon->targetlist) && rcon->rv_cache[varattno] != NULL) { /* Just copy the entry and fall through to adjust phlevelsup etc */ newnode = copyObject(rcon->rv_cache[varattno]); } else { /* * Generate the replacement expression. This takes care of expanding * wholerow references and dealing with non-default varreturningtype. */ newnode = ReplaceVarFromTargetList(var, rcon->target_rte, rcon->targetlist, rcon->result_relation, REPLACEVARS_REPORT_ERROR, 0); /* Insert PlaceHolderVar if needed */ if (need_phv) { bool wrap; if (rcon->wrap_option == REPLACE_WRAP_ALL) { /* Caller told us to wrap all expressions in a PlaceHolderVar */ wrap = true; } else if (varattno == InvalidAttrNumber) { /* * Insert PlaceHolderVar for whole-tuple reference. Notice * that we are wrapping one PlaceHolderVar around the whole * RowExpr, rather than putting one around each element of the * row. This is because we need the expression to yield NULL, * not ROW(NULL,NULL,...) when it is forced to null by an * outer join. */ wrap = true; } else if (newnode && IsA(newnode, Var) && ((Var *) newnode)->varlevelsup == 0) { /* * Simple Vars always escape being wrapped, unless they are * lateral references to something outside the subquery being * pulled up and the referenced rel is not under the same * lowest nulling outer join. */ wrap = false; if (rcon->target_rte->lateral && !bms_is_member(((Var *) newnode)->varno, rcon->relids)) { nullingrel_info *nullinfo = rcon->nullinfo; int lvarno = ((Var *) newnode)->varno; Assert(lvarno > 0 && lvarno <= nullinfo->rtlength); if (!bms_is_subset(nullinfo->nullingrels[rcon->varno], nullinfo->nullingrels[lvarno])) wrap = true; } } else if (newnode && IsA(newnode, PlaceHolderVar) && ((PlaceHolderVar *) newnode)->phlevelsup == 0) { /* The same rules apply for a PlaceHolderVar */ wrap = false; if (rcon->target_rte->lateral && !bms_is_subset(((PlaceHolderVar *) newnode)->phrels, rcon->relids)) { nullingrel_info *nullinfo = rcon->nullinfo; Relids lvarnos = ((PlaceHolderVar *) newnode)->phrels; int lvarno; lvarno = -1; while ((lvarno = bms_next_member(lvarnos, lvarno)) >= 0) { Assert(lvarno > 0 && lvarno <= nullinfo->rtlength); if (!bms_is_subset(nullinfo->nullingrels[rcon->varno], nullinfo->nullingrels[lvarno])) { wrap = true; break; } } } } else { /* * If the node contains Var(s) or PlaceHolderVar(s) of the * subquery being pulled up, or of rels that are under the * same lowest nulling outer join as the subquery, and does * not contain any non-strict constructs, then instead of * adding a PHV on top we can add the required nullingrels to * those Vars/PHVs. (This is fundamentally a generalization * of the above cases for bare Vars and PHVs.) * * This test is somewhat expensive, but it avoids pessimizing * the plan in cases where the nullingrels get removed again * later by outer join reduction. * * Note that we don't force wrapping of expressions containing * lateral references, so long as they also contain Vars/PHVs * of the subquery, or of rels that are under the same lowest * nulling outer join as the subquery. This is okay because * of the restriction to strict constructs: if those Vars/PHVs * have been forced to NULL by an outer join then the end * result of the expression will be NULL too, regardless of * the lateral references. So it's not necessary to force the * expression to be evaluated below the outer join. This can * be a very valuable optimization, because it may allow us to * avoid using a nested loop to pass the lateral reference * down. * * This analysis could be tighter: in particular, a non-strict * construct hidden within a lower-level PlaceHolderVar is not * reason to add another PHV. But for now it doesn't seem * worth the code to be more exact. This is also why it's * preferable to handle bare PHVs in the above branch, rather * than this branch. We also prefer to handle bare Vars in a * separate branch, as it's cheaper this way and parallels the * handling of PHVs. * * For a LATERAL subquery, we have to check the actual var * membership of the node, but if it's non-lateral then any * level-zero var must belong to the subquery. */ bool contain_nullable_vars = false; if (!rcon->target_rte->lateral) { if (contain_vars_of_level(newnode, 0)) contain_nullable_vars = true; } else { Relids all_varnos; all_varnos = pull_varnos(rcon->root, newnode); if (bms_overlap(all_varnos, rcon->relids)) contain_nullable_vars = true; else { nullingrel_info *nullinfo = rcon->nullinfo; int varno; varno = -1; while ((varno = bms_next_member(all_varnos, varno)) >= 0) { Assert(varno > 0 && varno <= nullinfo->rtlength); if (bms_is_subset(nullinfo->nullingrels[rcon->varno], nullinfo->nullingrels[varno])) { contain_nullable_vars = true; break; } } } } if (contain_nullable_vars && !contain_nonstrict_functions(newnode)) { /* No wrap needed */ wrap = false; } else { /* Else wrap it in a PlaceHolderVar */ wrap = true; } } if (wrap) { newnode = (Node *) make_placeholder_expr(rcon->root, (Expr *) newnode, bms_make_singleton(rcon->varno)); /* * Cache it if possible (ie, if the attno is in range, which * it probably always should be). */ if (varattno >= InvalidAttrNumber && varattno <= list_length(rcon->targetlist)) rcon->rv_cache[varattno] = copyObject(newnode); } } } /* Propagate any varnullingrels into the replacement expression */ if (var->varnullingrels != NULL) { if (IsA(newnode, Var)) { Var *newvar = (Var *) newnode; Assert(newvar->varlevelsup == 0); newvar->varnullingrels = bms_add_members(newvar->varnullingrels, var->varnullingrels); } else if (IsA(newnode, PlaceHolderVar)) { PlaceHolderVar *newphv = (PlaceHolderVar *) newnode; Assert(newphv->phlevelsup == 0); newphv->phnullingrels = bms_add_members(newphv->phnullingrels, var->varnullingrels); } else { /* * There should be Vars/PHVs within the expression that we can * modify. Vars/PHVs of the subquery should have the full * var->varnullingrels added to them, but if there are lateral * references within the expression, those must be marked with * only the nullingrels that potentially apply to them. (This * corresponds to the fact that the expression will now be * evaluated at the join level of the Var that we are replacing: * the lateral references may have bubbled up through fewer outer * joins than the subquery's Vars have. Per the discussion above, * we'll still get the right answers.) That relid set could be * different for different lateral relations, so we have to do * this work for each one. * * (Currently, the restrictions in is_simple_subquery() mean that * at most we have to remove the lowest outer join's relid from * the nullingrels of a lateral reference. However, we might * relax those restrictions someday, so let's do this right.) */ if (rcon->target_rte->lateral) { nullingrel_info *nullinfo = rcon->nullinfo; Relids lvarnos; int lvarno; /* * Identify lateral varnos used within newnode. We must do * this before injecting var->varnullingrels into the tree. */ lvarnos = pull_varnos(rcon->root, newnode); lvarnos = bms_del_members(lvarnos, rcon->relids); /* For each one, add relevant nullingrels if any */ lvarno = -1; while ((lvarno = bms_next_member(lvarnos, lvarno)) >= 0) { Relids lnullingrels; Assert(lvarno > 0 && lvarno <= nullinfo->rtlength); lnullingrels = bms_intersect(var->varnullingrels, nullinfo->nullingrels[lvarno]); if (!bms_is_empty(lnullingrels)) newnode = add_nulling_relids(newnode, bms_make_singleton(lvarno), lnullingrels); } } /* Finally, deal with Vars/PHVs of the subquery itself */ newnode = add_nulling_relids(newnode, rcon->relids, var->varnullingrels); /* Assert we did put the varnullingrels into the expression */ Assert(bms_is_subset(var->varnullingrels, pull_varnos(rcon->root, newnode))); } } /* Must adjust varlevelsup if replaced Var is within a subquery */ if (var->varlevelsup > 0) IncrementVarSublevelsUp(newnode, var->varlevelsup, 0); return newnode; } /* * Apply pullup variable replacement to a subquery * * This needs to be different from pullup_replace_vars() because * replace_rte_variables will think that it shouldn't increment sublevels_up * before entering the Query; so we need to call it with sublevels_up == 1. */ static Query * pullup_replace_vars_subquery(Query *query, pullup_replace_vars_context *context) { Assert(IsA(query, Query)); return (Query *) replace_rte_variables((Node *) query, context->varno, 1, pullup_replace_vars_callback, context, NULL); } /* * flatten_simple_union_all * Try to optimize top-level UNION ALL structure into an appendrel * * If a query's setOperations tree consists entirely of simple UNION ALL * operations, flatten it into an append relation, which we can process more * intelligently than the general setops case. Otherwise, do nothing. * * In most cases, this can succeed only for a top-level query, because for a * subquery in FROM, the parent query's invocation of pull_up_subqueries would * already have flattened the UNION via pull_up_simple_union_all. But there * are a few cases we can support here but not in that code path, for example * when the subquery also contains ORDER BY. */ void flatten_simple_union_all(PlannerInfo *root) { Query *parse = root->parse; SetOperationStmt *topop; Node *leftmostjtnode; int leftmostRTI; RangeTblEntry *leftmostRTE; int childRTI; RangeTblEntry *childRTE; RangeTblRef *rtr; /* Shouldn't be called unless query has setops */ topop = castNode(SetOperationStmt, parse->setOperations); Assert(topop); /* Can't optimize away a recursive UNION */ if (root->hasRecursion) return; /* * Recursively check the tree of set operations. If not all UNION ALL * with identical column types, punt. */ if (!is_simple_union_all_recurse((Node *) topop, parse, topop->colTypes)) return; /* * Locate the leftmost leaf query in the setops tree. The upper query's * Vars all refer to this RTE (see transformSetOperationStmt). */ leftmostjtnode = topop->larg; while (leftmostjtnode && IsA(leftmostjtnode, SetOperationStmt)) leftmostjtnode = ((SetOperationStmt *) leftmostjtnode)->larg; Assert(leftmostjtnode && IsA(leftmostjtnode, RangeTblRef)); leftmostRTI = ((RangeTblRef *) leftmostjtnode)->rtindex; leftmostRTE = rt_fetch(leftmostRTI, parse->rtable); Assert(leftmostRTE->rtekind == RTE_SUBQUERY); /* * Make a copy of the leftmost RTE and add it to the rtable. This copy * will represent the leftmost leaf query in its capacity as a member of * the appendrel. The original will represent the appendrel as a whole. * (We must do things this way because the upper query's Vars have to be * seen as referring to the whole appendrel.) */ childRTE = copyObject(leftmostRTE); parse->rtable = lappend(parse->rtable, childRTE); childRTI = list_length(parse->rtable); /* Modify the setops tree to reference the child copy */ ((RangeTblRef *) leftmostjtnode)->rtindex = childRTI; /* Modify the formerly-leftmost RTE to mark it as an appendrel parent */ leftmostRTE->inh = true; /* * Form a RangeTblRef for the appendrel, and insert it into FROM. The top * Query of a setops tree should have had an empty FromClause initially. */ rtr = makeNode(RangeTblRef); rtr->rtindex = leftmostRTI; Assert(parse->jointree->fromlist == NIL); parse->jointree->fromlist = list_make1(rtr); /* * Now pretend the query has no setops. We must do this before trying to * do subquery pullup, because of Assert in pull_up_simple_subquery. */ parse->setOperations = NULL; /* * Build AppendRelInfo information, and apply pull_up_subqueries to the * leaf queries of the UNION ALL. (We must do that now because they * weren't previously referenced by the jointree, and so were missed by * the main invocation of pull_up_subqueries.) */ pull_up_union_leaf_queries((Node *) topop, root, leftmostRTI, parse, 0); } /* * 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.) * * Another transformation we apply here is to recognize cases like * SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL; * If the join clause is strict for b.y, then only null-extended rows could * pass the upper WHERE, and we can conclude that what the query is really * specifying is an anti-semijoin. We change the join type from JOIN_LEFT * to JOIN_ANTI. The IS NULL clause then becomes redundant, and must be * removed to prevent bogus selectivity calculations, but we leave it to * distribute_qual_to_rels to get rid of such clauses. * * Also, we get rid of JOIN_RIGHT cases by flipping them around to become * JOIN_LEFT. This saves some code here and in some later planner routines; * the main benefit is to reduce the number of jointypes that can appear in * SpecialJoinInfo nodes. Note that we can still generate Paths and Plans * that use JOIN_RIGHT (or JOIN_RIGHT_ANTI) by switching the inputs again. * * 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_pass1_state *state1; reduce_outer_joins_pass2_state state2; ListCell *lc; /* * 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. */ state1 = reduce_outer_joins_pass1((Node *) root->parse->jointree); /* planner.c shouldn't have called me if no outer joins */ if (state1 == NULL || !state1->contains_outer) elog(ERROR, "so where are the outer joins?"); state2.inner_reduced = NULL; state2.partial_reduced = NIL; reduce_outer_joins_pass2((Node *) root->parse->jointree, state1, &state2, root, NULL, NIL); /* * If we successfully reduced the strength of any outer joins, we must * remove references to those joins as nulling rels. This is handled as * an additional pass, for simplicity and because we can handle all * fully-reduced joins in a single pass over the parse tree. */ if (!bms_is_empty(state2.inner_reduced)) { root->parse = (Query *) remove_nulling_relids((Node *) root->parse, state2.inner_reduced, NULL); /* There could be references in the append_rel_list, too */ root->append_rel_list = (List *) remove_nulling_relids((Node *) root->append_rel_list, state2.inner_reduced, NULL); } /* * Partially-reduced full joins have to be done one at a time, since * they'll each need a different setting of except_relids. */ foreach(lc, state2.partial_reduced) { reduce_outer_joins_partial_state *statep = lfirst(lc); Relids full_join_relids = bms_make_singleton(statep->full_join_rti); root->parse = (Query *) remove_nulling_relids((Node *) root->parse, full_join_relids, statep->unreduced_side); root->append_rel_list = (List *) remove_nulling_relids((Node *) root->append_rel_list, full_join_relids, statep->unreduced_side); } } /* * reduce_outer_joins_pass1 - phase 1 data collection * * Returns a state node describing the given jointree node. */ static reduce_outer_joins_pass1_state * reduce_outer_joins_pass1(Node *jtnode) { reduce_outer_joins_pass1_state *result; result = (reduce_outer_joins_pass1_state *) palloc(sizeof(reduce_outer_joins_pass1_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_pass1_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_pass1_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 * state1: state data collected by phase 1 for this node * state2: where to accumulate info about successfully-reduced joins * root: toplevel planner state * nonnullable_rels: set of base relids forced non-null by upper quals * forced_null_vars: multibitmapset of Vars forced null by upper quals * * Returns info in state2 about outer joins that were successfully simplified. * Joins that were fully reduced to inner joins are all added to * state2->inner_reduced. If a full join is reduced to a left join, * it needs its own entry in state2->partial_reduced, since that will * require custom processing to remove only the correct nullingrel markers. */ static void reduce_outer_joins_pass2(Node *jtnode, reduce_outer_joins_pass1_state *state1, reduce_outer_joins_pass2_state *state2, PlannerInfo *root, Relids nonnullable_rels, List *forced_null_vars) { /* * 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_rels; List *pass_forced_null_vars; /* Scan quals to see if we can add any constraints */ pass_nonnullable_rels = find_nonnullable_rels(f->quals); pass_nonnullable_rels = bms_add_members(pass_nonnullable_rels, nonnullable_rels); pass_forced_null_vars = find_forced_null_vars(f->quals); pass_forced_null_vars = mbms_add_members(pass_forced_null_vars, forced_null_vars); /* And recurse --- but only into interesting subtrees */ Assert(list_length(f->fromlist) == list_length(state1->sub_states)); forboth(l, f->fromlist, s, state1->sub_states) { reduce_outer_joins_pass1_state *sub_state = lfirst(s); if (sub_state->contains_outer) reduce_outer_joins_pass2(lfirst(l), sub_state, state2, root, pass_nonnullable_rels, pass_forced_null_vars); } bms_free(pass_nonnullable_rels); /* can't so easily clean up var lists, unfortunately */ } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; int rtindex = j->rtindex; JoinType jointype = j->jointype; reduce_outer_joins_pass1_state *left_state = linitial(state1->sub_states); reduce_outer_joins_pass1_state *right_state = lsecond(state1->sub_states); /* Can we simplify this join? */ switch (jointype) { case JOIN_INNER: break; 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; /* Also report partial reduction in state2 */ report_reduced_full_join(state2, rtindex, right_state->relids); } } else { if (bms_overlap(nonnullable_rels, right_state->relids)) { jointype = JOIN_RIGHT; /* Also report partial reduction in state2 */ report_reduced_full_join(state2, rtindex, left_state->relids); } } break; case JOIN_SEMI: case JOIN_ANTI: /* * These could only have been introduced by pull_up_sublinks, * so there's no way that upper quals could refer to their * righthand sides, and no point in checking. We don't expect * to see JOIN_RIGHT_SEMI or JOIN_RIGHT_ANTI yet. */ break; default: elog(ERROR, "unrecognized join type: %d", (int) jointype); break; } /* * Convert JOIN_RIGHT to JOIN_LEFT. Note that in the case where we * reduced JOIN_FULL to JOIN_RIGHT, this will mean the JoinExpr no * longer matches the internal ordering of any CoalesceExpr's built to * represent merged join variables. We don't care about that at * present, but be wary of it ... */ if (jointype == JOIN_RIGHT) { Node *tmparg; tmparg = j->larg; j->larg = j->rarg; j->rarg = tmparg; jointype = JOIN_LEFT; right_state = linitial(state1->sub_states); left_state = lsecond(state1->sub_states); } /* * See if we can reduce JOIN_LEFT to JOIN_ANTI. This is the case if * the join's own quals are strict for any var that was forced null by * higher qual levels. NOTE: there are other ways that we could * detect an anti-join, in particular if we were to check whether Vars * coming from the RHS must be non-null because of table constraints. * That seems complicated and expensive though (in particular, one * would have to be wary of lower outer joins). For the moment this * seems sufficient. */ if (jointype == JOIN_LEFT) { List *nonnullable_vars; Bitmapset *overlap; /* Find Vars in j->quals that must be non-null in joined rows */ nonnullable_vars = find_nonnullable_vars(j->quals); /* * It's not sufficient to check whether nonnullable_vars and * forced_null_vars overlap: we need to know if the overlap * includes any RHS variables. */ overlap = mbms_overlap_sets(nonnullable_vars, forced_null_vars); if (bms_overlap(overlap, right_state->relids)) jointype = JOIN_ANTI; } /* * Apply the jointype change, if any, to both jointree node and RTE. * Also, if we changed an RTE to INNER, add its RTI to inner_reduced. */ if (rtindex && jointype != j->jointype) { RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable); Assert(rte->rtekind == RTE_JOIN); Assert(rte->jointype == j->jointype); rte->jointype = jointype; if (jointype == JOIN_INNER) state2->inner_reduced = bms_add_member(state2->inner_reduced, rtindex); } 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_rels; List *local_forced_null_vars; Relids pass_nonnullable_rels; List *pass_forced_null_vars; /* * If this join is (now) inner, we can add any constraints its * quals provide to those we got from above. But if it is outer, * we can pass down the local constraints only into the nullable * side, because an outer join never eliminates any rows from its * non-nullable side. Also, there is no point in passing upper * constraints into the nullable side, since if there were any * we'd have been able to reduce the join. (In the case of upper * forced-null constraints, we *must not* pass them into the * nullable side --- they either applied here, or not.) The upshot * is that we pass either the local or the upper constraints, * never both, to the children of an outer join. * * Note that a SEMI join works like an inner join here: it's okay * to pass down both local and upper constraints. (There can't be * any upper constraints affecting its inner side, but it's not * worth having a separate code path to avoid passing them.) * * At a FULL join we just punt and pass nothing down --- is it * possible to be smarter? */ if (jointype != JOIN_FULL) { local_nonnullable_rels = find_nonnullable_rels(j->quals); local_forced_null_vars = find_forced_null_vars(j->quals); if (jointype == JOIN_INNER || jointype == JOIN_SEMI) { /* OK to merge upper and local constraints */ local_nonnullable_rels = bms_add_members(local_nonnullable_rels, nonnullable_rels); local_forced_null_vars = mbms_add_members(local_forced_null_vars, forced_null_vars); } } else { /* no use in calculating these */ local_nonnullable_rels = NULL; local_forced_null_vars = NIL; } if (left_state->contains_outer) { if (jointype == JOIN_INNER || jointype == JOIN_SEMI) { /* pass union of local and upper constraints */ pass_nonnullable_rels = local_nonnullable_rels; pass_forced_null_vars = local_forced_null_vars; } else if (jointype != JOIN_FULL) /* ie, LEFT or ANTI */ { /* can't pass local constraints to non-nullable side */ pass_nonnullable_rels = nonnullable_rels; pass_forced_null_vars = forced_null_vars; } else { /* no constraints pass through JOIN_FULL */ pass_nonnullable_rels = NULL; pass_forced_null_vars = NIL; } reduce_outer_joins_pass2(j->larg, left_state, state2, root, pass_nonnullable_rels, pass_forced_null_vars); } if (right_state->contains_outer) { if (jointype != JOIN_FULL) /* ie, INNER/LEFT/SEMI/ANTI */ { /* pass appropriate constraints, per comment above */ pass_nonnullable_rels = local_nonnullable_rels; pass_forced_null_vars = local_forced_null_vars; } else { /* no constraints pass through JOIN_FULL */ pass_nonnullable_rels = NULL; pass_forced_null_vars = NIL; } reduce_outer_joins_pass2(j->rarg, right_state, state2, root, pass_nonnullable_rels, pass_forced_null_vars); } bms_free(local_nonnullable_rels); } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /* Helper for reduce_outer_joins_pass2 */ static void report_reduced_full_join(reduce_outer_joins_pass2_state *state2, int rtindex, Relids relids) { reduce_outer_joins_partial_state *statep; statep = palloc(sizeof(reduce_outer_joins_partial_state)); statep->full_join_rti = rtindex; statep->unreduced_side = relids; state2->partial_reduced = lappend(state2->partial_reduced, statep); } /* * remove_useless_result_rtes * Attempt to remove RTE_RESULT RTEs from the join tree. * Also, elide single-child FromExprs where possible. * * We can remove RTE_RESULT entries from the join tree using the knowledge * that RTE_RESULT returns exactly one row and has no output columns. Hence, * if one is inner-joined to anything else, we can delete it. Optimizations * are also possible for some outer-join cases, as detailed below. * * This pass also replaces single-child FromExprs with their child node * where possible. It's appropriate to do that here and not earlier because * RTE_RESULT removal might reduce a multiple-child FromExpr to have only one * child. We can remove such a FromExpr if its quals are empty, or if it's * semantically valid to merge the quals into those of the parent node. * While removing unnecessary join tree nodes has some micro-efficiency value, * the real reason to do this is to eliminate cases where the nullable side of * an outer join node is a FromExpr whose single child is another outer join. * To correctly determine whether the two outer joins can commute, * deconstruct_jointree() must treat any quals of such a FromExpr as being * degenerate quals of the upper outer join. The best way to do that is to * make them actually *be* quals of the upper join, by dropping the FromExpr * and hoisting the quals up into the upper join's quals. (Note that there is * no hazard when the intermediate FromExpr has multiple children, since then * it represents an inner join that cannot commute with the upper outer join.) * As long as we have to do that, we might as well elide such FromExprs * everywhere. * * Some of these optimizations depend on recognizing empty (constant-true) * quals for FromExprs and JoinExprs. That makes it useful to apply this * optimization pass after expression preprocessing, since that will have * eliminated constant-true quals, allowing more cases to be recognized as * optimizable. What's more, the usual reason for an RTE_RESULT to be present * is that we pulled up a subquery or VALUES clause, thus very possibly * replacing Vars with constants, making it more likely that a qual can be * reduced to constant true. Also, because some optimizations depend on * the outer-join type, it's best to have done reduce_outer_joins() first. * * A PlaceHolderVar referencing an RTE_RESULT RTE poses an obstacle to this * process: we must remove the RTE_RESULT's relid from the PHV's phrels, but * we must not reduce the phrels set to empty. If that would happen, and * the RTE_RESULT is an immediate child of an outer join, we have to give up * and not remove the RTE_RESULT: there is noplace else to evaluate the * PlaceHolderVar. (That is, in such cases the RTE_RESULT *does* have output * columns.) But if the RTE_RESULT is an immediate child of an inner join, * we can usually change the PlaceHolderVar's phrels so as to evaluate it at * the inner join instead. This is OK because we really only care that PHVs * are evaluated above or below the correct outer joins. We can't, however, * postpone the evaluation of a PHV to above where it is used; so there are * some checks below on whether output PHVs are laterally referenced in the * other join input rel(s). * * We used to try to do this work as part of pull_up_subqueries() where the * potentially-optimizable cases get introduced; but it's way simpler, and * more effective, to do it separately. */ void remove_useless_result_rtes(PlannerInfo *root) { Relids dropped_outer_joins = NULL; ListCell *cell; /* Top level of jointree must always be a FromExpr */ Assert(IsA(root->parse->jointree, FromExpr)); /* Recurse ... */ root->parse->jointree = (FromExpr *) remove_useless_results_recurse(root, (Node *) root->parse->jointree, NULL, &dropped_outer_joins); /* We should still have a FromExpr */ Assert(IsA(root->parse->jointree, FromExpr)); /* * If we removed any outer-join nodes from the jointree, run around and * remove references to those joins as nulling rels. (There could be such * references in PHVs that we pulled up out of the original subquery that * the RESULT rel replaced. This is kosher on the grounds that we now * know that such an outer join wouldn't really have nulled anything.) We * don't do this during the main recursion, for simplicity and because we * can handle all such joins in a single pass over the parse tree. */ if (!bms_is_empty(dropped_outer_joins)) { root->parse = (Query *) remove_nulling_relids((Node *) root->parse, dropped_outer_joins, NULL); /* There could be references in the append_rel_list, too */ root->append_rel_list = (List *) remove_nulling_relids((Node *) root->append_rel_list, dropped_outer_joins, NULL); } /* * Remove any PlanRowMark referencing an RTE_RESULT RTE. We obviously * must do that for any RTE_RESULT that we just removed. But one for a * RTE that we did not remove can be dropped anyway: since the RTE has * only one possible output row, there is no need for EPQ to mark and * restore that row. * * It's necessary, not optional, to remove the PlanRowMark for a surviving * RTE_RESULT RTE; otherwise we'll generate a whole-row Var for the * RTE_RESULT, which the executor has no support for. */ foreach(cell, root->rowMarks) { PlanRowMark *rc = (PlanRowMark *) lfirst(cell); if (rt_fetch(rc->rti, root->parse->rtable)->rtekind == RTE_RESULT) root->rowMarks = foreach_delete_current(root->rowMarks, cell); } } /* * remove_useless_results_recurse * Recursive guts of remove_useless_result_rtes. * * This recursively processes the jointree and returns a modified jointree. * In addition, the RT indexes of any removed outer-join nodes are added to * *dropped_outer_joins. * * jtnode is the current jointree node. If it could be valid to merge * its quals into those of the parent node, parent_quals should point to * the parent's quals list; otherwise, pass NULL for parent_quals. * (Note that in some cases, parent_quals points to the quals of a parent * more than one level up in the tree.) */ static Node * remove_useless_results_recurse(PlannerInfo *root, Node *jtnode, Node **parent_quals, Relids *dropped_outer_joins) { Assert(jtnode != NULL); if (IsA(jtnode, RangeTblRef)) { /* Can't immediately do anything with a RangeTblRef */ } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; Relids result_relids = NULL; ListCell *cell; /* * We can drop RTE_RESULT rels from the fromlist so long as at least * one child remains, since joining to a one-row table changes * nothing. (But we can't drop a RTE_RESULT that computes PHV(s) that * are needed by some sibling. The cleanup transformation below would * reassign the PHVs to be computed at the join, which is too late for * the sibling's use.) The easiest way to mechanize this rule is to * modify the list in-place. */ foreach(cell, f->fromlist) { Node *child = (Node *) lfirst(cell); int varno; /* Recursively transform child, allowing it to push up quals ... */ child = remove_useless_results_recurse(root, child, &f->quals, dropped_outer_joins); /* ... and stick it back into the tree */ lfirst(cell) = child; /* * If it's an RTE_RESULT with at least one sibling, and no sibling * references dependent PHVs, we can drop it. We don't yet know * what the inner join's final relid set will be, so postpone * cleanup of PHVs etc till after this loop. */ if (list_length(f->fromlist) > 1 && (varno = get_result_relid(root, child)) != 0 && !find_dependent_phvs_in_jointree(root, (Node *) f, varno)) { f->fromlist = foreach_delete_current(f->fromlist, cell); result_relids = bms_add_member(result_relids, varno); } } /* * Clean up if we dropped any RTE_RESULT RTEs. This is a bit * inefficient if there's more than one, but it seems better to * optimize the support code for the single-relid case. */ if (result_relids) { int varno = -1; while ((varno = bms_next_member(result_relids, varno)) >= 0) remove_result_refs(root, varno, (Node *) f); } /* * If the FromExpr now has only one child, see if we can elide it. * This is always valid if there are no quals, except at the top of * the jointree (since Query.jointree is required to point to a * FromExpr). Otherwise, we can do it if we can push the quals up to * the parent node. * * Note: while it would not be terribly hard to generalize this * transformation to merge multi-child FromExprs into their parent * FromExpr, that risks making the parent join too expensive to plan. * We leave it to later processing to decide heuristically whether * that's a good idea. Pulling up a single child is always OK, * however. */ if (list_length(f->fromlist) == 1 && f != root->parse->jointree && (f->quals == NULL || parent_quals != NULL)) { /* * Merge any quals up to parent. They should be in implicit-AND * format by now, so we just need to concatenate lists. Put the * child quals at the front, on the grounds that they should * nominally be evaluated earlier. */ if (f->quals != NULL) *parent_quals = (Node *) list_concat(castNode(List, f->quals), castNode(List, *parent_quals)); return (Node *) linitial(f->fromlist); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; int varno; /* * First, recurse. We can absorb pushed-up FromExpr quals from either * child into this node if the jointype is INNER, since then this is * equivalent to a FromExpr. When the jointype is LEFT, we can absorb * quals from the RHS child into the current node, as they're * essentially degenerate quals of the outer join. Moreover, if we've * been passed down a parent_quals pointer then we can allow quals of * the LHS child to be absorbed into the parent. (This is important * to ensure we remove single-child FromExprs immediately below * commutable left joins.) For other jointypes, we can't move child * quals up, or at least there's no particular reason to. */ j->larg = remove_useless_results_recurse(root, j->larg, (j->jointype == JOIN_INNER) ? &j->quals : (j->jointype == JOIN_LEFT) ? parent_quals : NULL, dropped_outer_joins); j->rarg = remove_useless_results_recurse(root, j->rarg, (j->jointype == JOIN_INNER || j->jointype == JOIN_LEFT) ? &j->quals : NULL, dropped_outer_joins); /* Apply join-type-specific optimization rules */ switch (j->jointype) { case JOIN_INNER: /* * An inner join is equivalent to a FromExpr, so if either * side was simplified to an RTE_RESULT rel, we can replace * the join with a FromExpr with just the other side. * Furthermore, we can elide that FromExpr according to the * same rules as above. * * Just as in the FromExpr case, we can't simplify if the * other input rel references any PHVs that are marked as to * be evaluated at the RTE_RESULT rel, because we can't * postpone their evaluation in that case. But we only have * to check this in cases where it's syntactically legal for * the other input to have a LATERAL reference to the * RTE_RESULT rel. Only RHSes of inner and left joins are * allowed to have such refs. */ if ((varno = get_result_relid(root, j->larg)) != 0 && !find_dependent_phvs_in_jointree(root, j->rarg, varno)) { remove_result_refs(root, varno, j->rarg); if (j->quals != NULL && parent_quals == NULL) jtnode = (Node *) makeFromExpr(list_make1(j->rarg), j->quals); else { /* Merge any quals up to parent */ if (j->quals != NULL) *parent_quals = (Node *) list_concat(castNode(List, j->quals), castNode(List, *parent_quals)); jtnode = j->rarg; } } else if ((varno = get_result_relid(root, j->rarg)) != 0) { remove_result_refs(root, varno, j->larg); if (j->quals != NULL && parent_quals == NULL) jtnode = (Node *) makeFromExpr(list_make1(j->larg), j->quals); else { /* Merge any quals up to parent */ if (j->quals != NULL) *parent_quals = (Node *) list_concat(castNode(List, j->quals), castNode(List, *parent_quals)); jtnode = j->larg; } } break; case JOIN_LEFT: /* * We can simplify this case if the RHS is an RTE_RESULT, with * two different possibilities: * * If the qual is empty (JOIN ON TRUE), then the join can be * strength-reduced to a plain inner join, since each LHS row * necessarily has exactly one join partner. So we can always * discard the RHS, much as in the JOIN_INNER case above. * (Again, the LHS could not contain a lateral reference to * the RHS.) * * Otherwise, it's still true that each LHS row should be * returned exactly once, and since the RHS returns no columns * (unless there are PHVs that have to be evaluated there), we * don't much care if it's null-extended or not. So in this * case also, we can just ignore the qual and discard the left * join. */ if ((varno = get_result_relid(root, j->rarg)) != 0 && (j->quals == NULL || !find_dependent_phvs(root, varno))) { remove_result_refs(root, varno, j->larg); *dropped_outer_joins = bms_add_member(*dropped_outer_joins, j->rtindex); jtnode = j->larg; } break; case JOIN_SEMI: /* * We may simplify this case if the RHS is an RTE_RESULT; the * join qual becomes effectively just a filter qual for the * LHS, since we should either return the LHS row or not. The * filter clause must go into a new FromExpr if we can't push * it up to the parent. * * There is a fine point about PHVs that are supposed to be * evaluated at the RHS. Such PHVs could only appear in the * semijoin's qual, since the rest of the query cannot * reference any outputs of the semijoin's RHS. Therefore, * they can't actually go to null before being examined, and * it'd be OK to just remove the PHV wrapping. We don't have * infrastructure for that, but remove_result_refs() will * relabel them as to be evaluated at the LHS, which is fine. * * Also, we don't need to worry about removing traces of the * join's rtindex, since it hasn't got one. */ if ((varno = get_result_relid(root, j->rarg)) != 0) { Assert(j->rtindex == 0); remove_result_refs(root, varno, j->larg); if (j->quals != NULL && parent_quals == NULL) jtnode = (Node *) makeFromExpr(list_make1(j->larg), j->quals); else { /* Merge any quals up to parent */ if (j->quals != NULL) *parent_quals = (Node *) list_concat(castNode(List, j->quals), castNode(List, *parent_quals)); jtnode = j->larg; } } break; case JOIN_FULL: case JOIN_ANTI: /* We have no special smarts for these cases */ break; default: /* Note: JOIN_RIGHT should be gone at this point */ elog(ERROR, "unrecognized join type: %d", (int) j->jointype); break; } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return jtnode; } /* * get_result_relid * If jtnode is a RangeTblRef for an RTE_RESULT RTE, return its relid; * otherwise return 0. */ static int get_result_relid(PlannerInfo *root, Node *jtnode) { int varno; if (!IsA(jtnode, RangeTblRef)) return 0; varno = ((RangeTblRef *) jtnode)->rtindex; if (rt_fetch(varno, root->parse->rtable)->rtekind != RTE_RESULT) return 0; return varno; } /* * remove_result_refs * Helper routine for dropping an unneeded RTE_RESULT RTE. * * This doesn't physically remove the RTE from the jointree, because that's * more easily handled in remove_useless_results_recurse. What it does do * is the necessary cleanup in the rest of the tree: we must adjust any PHVs * that may reference the RTE. Be sure to call this at a point where the * jointree is valid (no disconnected nodes). * * Note that we don't need to process the append_rel_list, since RTEs * referenced directly in the jointree won't be appendrel members. * * varno is the RTE_RESULT's relid. * newjtloc is the jointree location at which any PHVs referencing the * RTE_RESULT should be evaluated instead. */ static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc) { /* Fix up PlaceHolderVars as needed */ /* If there are no PHVs anywhere, we can skip this bit */ if (root->glob->lastPHId != 0) { Relids subrelids; subrelids = get_relids_in_jointree(newjtloc, true, false); Assert(!bms_is_empty(subrelids)); substitute_phv_relids((Node *) root->parse, varno, subrelids); fix_append_rel_relids(root, varno, subrelids); } /* * We also need to remove any PlanRowMark referencing the RTE, but we * postpone that work until we return to remove_useless_result_rtes. */ } /* * find_dependent_phvs - are there any PlaceHolderVars whose relids are * exactly the given varno? * * find_dependent_phvs should be used when we want to see if there are * any such PHVs anywhere in the Query. Another use-case is to see if * a subtree of the join tree contains such PHVs; but for that, we have * to look not only at the join tree nodes themselves but at the * referenced RTEs. For that, use find_dependent_phvs_in_jointree. */ typedef struct { Relids relids; int sublevels_up; } find_dependent_phvs_context; static bool find_dependent_phvs_walker(Node *node, find_dependent_phvs_context *context) { if (node == NULL) return false; if (IsA(node, PlaceHolderVar)) { PlaceHolderVar *phv = (PlaceHolderVar *) node; if (phv->phlevelsup == context->sublevels_up && bms_equal(context->relids, phv->phrels)) return true; /* fall through to examine children */ } if (IsA(node, Query)) { /* Recurse into subselects */ bool result; context->sublevels_up++; result = query_tree_walker((Query *) node, find_dependent_phvs_walker, context, 0); context->sublevels_up--; return result; } /* Shouldn't need to handle most planner auxiliary nodes here */ Assert(!IsA(node, SpecialJoinInfo)); Assert(!IsA(node, PlaceHolderInfo)); Assert(!IsA(node, MinMaxAggInfo)); return expression_tree_walker(node, find_dependent_phvs_walker, context); } static bool find_dependent_phvs(PlannerInfo *root, int varno) { find_dependent_phvs_context context; /* If there are no PHVs anywhere, we needn't work hard */ if (root->glob->lastPHId == 0) return false; context.relids = bms_make_singleton(varno); context.sublevels_up = 0; if (query_tree_walker(root->parse, find_dependent_phvs_walker, &context, 0)) return true; /* The append_rel_list could be populated already, so check it too */ if (expression_tree_walker((Node *) root->append_rel_list, find_dependent_phvs_walker, &context)) return true; return false; } static bool find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno) { find_dependent_phvs_context context; Relids subrelids; int relid; /* If there are no PHVs anywhere, we needn't work hard */ if (root->glob->lastPHId == 0) return false; context.relids = bms_make_singleton(varno); context.sublevels_up = 0; /* * See if the jointree fragment itself contains references (in join quals) */ if (find_dependent_phvs_walker(node, &context)) return true; /* * Otherwise, identify the set of referenced RTEs (we can ignore joins, * since they should be flattened already, so their join alias lists no * longer matter), and tediously check each RTE. We can ignore RTEs that * are not marked LATERAL, though, since they couldn't possibly contain * any cross-references to other RTEs. */ subrelids = get_relids_in_jointree(node, false, false); relid = -1; while ((relid = bms_next_member(subrelids, relid)) >= 0) { RangeTblEntry *rte = rt_fetch(relid, root->parse->rtable); if (rte->lateral && range_table_entry_walker(rte, find_dependent_phvs_walker, &context, 0)) return true; } return false; } /* * substitute_phv_relids - adjust PlaceHolderVar relid sets after pulling up * a subquery or removing an RTE_RESULT jointree item * * Find any PlaceHolderVar nodes in the given tree that reference the * pulled-up relid, and change them to reference the replacement relid(s). * * NOTE: although this has the form of a walker, we cheat and modify the * nodes in-place. This should be OK since the tree was copied by * pullup_replace_vars earlier. Avoid scribbling on the original values of * the bitmapsets, though, because expression_tree_mutator doesn't copy those. */ typedef struct { int varno; int sublevels_up; Relids subrelids; } substitute_phv_relids_context; static bool substitute_phv_relids_walker(Node *node, substitute_phv_relids_context *context) { if (node == NULL) return false; if (IsA(node, PlaceHolderVar)) { PlaceHolderVar *phv = (PlaceHolderVar *) node; if (phv->phlevelsup == context->sublevels_up && bms_is_member(context->varno, phv->phrels)) { phv->phrels = bms_union(phv->phrels, context->subrelids); phv->phrels = bms_del_member(phv->phrels, context->varno); /* Assert we haven't broken the PHV */ Assert(!bms_is_empty(phv->phrels)); } /* fall through to examine children */ } if (IsA(node, Query)) { /* Recurse into subselects */ bool result; context->sublevels_up++; result = query_tree_walker((Query *) node, substitute_phv_relids_walker, context, 0); context->sublevels_up--; return result; } /* Shouldn't need to handle planner auxiliary nodes here */ Assert(!IsA(node, SpecialJoinInfo)); Assert(!IsA(node, AppendRelInfo)); Assert(!IsA(node, PlaceHolderInfo)); Assert(!IsA(node, MinMaxAggInfo)); return expression_tree_walker(node, substitute_phv_relids_walker, context); } static void substitute_phv_relids(Node *node, int varno, Relids subrelids) { substitute_phv_relids_context context; context.varno = varno; context.sublevels_up = 0; context.subrelids = subrelids; /* * Must be prepared to start with a Query or a bare expression tree. */ query_or_expression_tree_walker(node, substitute_phv_relids_walker, &context, 0); } /* * 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 also need to apply substitute_phv_relids to their * translated_vars lists, since those might contain PlaceHolderVars. * * We assume we may modify the AppendRelInfo nodes in-place. */ static void fix_append_rel_relids(PlannerInfo *root, 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, root->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; } /* Also fix up any PHVs in its translated vars */ if (root->glob->lastPHId != 0) substitute_phv_relids((Node *) appinfo->translated_vars, varno, subrelids); } } /* * get_relids_in_jointree: get set of RT indexes present in a jointree * * Base-relation relids are always included in the result. * If include_outer_joins is true, outer-join RT indexes are included. * If include_inner_joins is true, inner-join RT indexes are included. * * Note that for most purposes in the planner, outer joins are included * in standard relid sets. Setting include_inner_joins true is only * appropriate for special purposes during subquery flattening. */ Relids get_relids_in_jointree(Node *jtnode, bool include_outer_joins, bool include_inner_joins) { 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), include_outer_joins, include_inner_joins)); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; result = get_relids_in_jointree(j->larg, include_outer_joins, include_inner_joins); result = bms_join(result, get_relids_in_jointree(j->rarg, include_outer_joins, include_inner_joins)); if (j->rtindex) { if (j->jointype == JOIN_INNER) { if (include_inner_joins) result = bms_add_member(result, j->rtindex); } else { if (include_outer_joins) result = bms_add_member(result, j->rtindex); } } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); return result; } /* * get_relids_for_join: get set of base+OJ RT indexes making up a join */ Relids get_relids_for_join(Query *query, int joinrelid) { Node *jtnode; jtnode = find_jointree_node_for_rel((Node *) query->jointree, joinrelid); if (!jtnode) elog(ERROR, "could not find join node %d", joinrelid); return get_relids_in_jointree(jtnode, true, false); } /* * 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; } /* * get_nullingrels: collect info about which outer joins null which relations * * The result struct contains, for each leaf relation used in the query, * the set of relids of outer joins that potentially null that rel. */ static nullingrel_info * get_nullingrels(Query *parse) { nullingrel_info *result = palloc_object(nullingrel_info); result->rtlength = list_length(parse->rtable); result->nullingrels = palloc0_array(Relids, result->rtlength + 1); get_nullingrels_recurse((Node *) parse->jointree, NULL, result); return result; } /* * Recursive guts of get_nullingrels(). * * Note: at any recursion level, the passed-down upper_nullingrels must be * treated as a constant, but it can be stored directly into *info * if we're at leaf level. Upper recursion levels do not free their mutated * copies of the nullingrels, because those are probably referenced by * at least one leaf rel. */ static void get_nullingrels_recurse(Node *jtnode, Relids upper_nullingrels, nullingrel_info *info) { if (jtnode == NULL) return; if (IsA(jtnode, RangeTblRef)) { int varno = ((RangeTblRef *) jtnode)->rtindex; Assert(varno > 0 && varno <= info->rtlength); info->nullingrels[varno] = upper_nullingrels; } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) { get_nullingrels_recurse(lfirst(l), upper_nullingrels, info); } } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; Relids local_nullingrels; switch (j->jointype) { case JOIN_INNER: get_nullingrels_recurse(j->larg, upper_nullingrels, info); get_nullingrels_recurse(j->rarg, upper_nullingrels, info); break; case JOIN_LEFT: case JOIN_SEMI: case JOIN_ANTI: local_nullingrels = bms_add_member(bms_copy(upper_nullingrels), j->rtindex); get_nullingrels_recurse(j->larg, upper_nullingrels, info); get_nullingrels_recurse(j->rarg, local_nullingrels, info); break; case JOIN_FULL: local_nullingrels = bms_add_member(bms_copy(upper_nullingrels), j->rtindex); get_nullingrels_recurse(j->larg, local_nullingrels, info); get_nullingrels_recurse(j->rarg, local_nullingrels, info); break; case JOIN_RIGHT: local_nullingrels = bms_add_member(bms_copy(upper_nullingrels), j->rtindex); get_nullingrels_recurse(j->larg, local_nullingrels, info); get_nullingrels_recurse(j->rarg, upper_nullingrels, info); break; default: elog(ERROR, "unrecognized join type: %d", (int) j->jointype); break; } } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); }