/*------------------------------------------------------------------------- * * rewriteHandler.c * * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.81 2000/09/29 18:21:24 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "catalog/pg_operator.h" #include "catalog/pg_type.h" #include "miscadmin.h" #include "nodes/makefuncs.h" #include "optimizer/clauses.h" #include "optimizer/prep.h" #include "optimizer/var.h" #include "parser/analyze.h" #include "parser/parse_expr.h" #include "parser/parse_oper.h" #include "parser/parse_target.h" #include "parser/parsetree.h" #include "parser/parse_type.h" #include "rewrite/rewriteManip.h" #include "utils/lsyscache.h" extern void CheckSelectForUpdate(Query *rule_action); /* in analyze.c */ static RewriteInfo *gatherRewriteMeta(Query *parsetree, Query *rule_action, Node *rule_qual, int rt_index, CmdType event, bool instead_flag); static List *adjustJoinTreeList(Query *parsetree, int rt_index, bool *found); static List *matchLocks(CmdType event, RuleLock *rulelocks, int varno, Query *parsetree); static Query *fireRIRrules(Query *parsetree); static Query *Except_Intersect_Rewrite(Query *parsetree); static void check_targetlists_are_compatible(List *prev_target, List *current_target); static void create_intersect_list(Node *ptr, List **intersect_list); static Node *intersect_tree_analyze(Node *tree, Node *first_select, Node *parsetree); /* * gatherRewriteMeta - * Gather meta information about parsetree, and rule. Fix rule body * and qualifier so that they can be mixed with the parsetree and * maintain semantic validity */ static RewriteInfo * gatherRewriteMeta(Query *parsetree, Query *rule_action, Node *rule_qual, int rt_index, CmdType event, bool instead_flag) { RewriteInfo *info; int rt_length; info = (RewriteInfo *) palloc(sizeof(RewriteInfo)); info->rt_index = rt_index; info->event = event; info->instead_flag = instead_flag; info->rule_action = (Query *) copyObject(rule_action); info->rule_qual = (Node *) copyObject(rule_qual); if (info->rule_action == NULL) info->nothing = TRUE; else { info->nothing = FALSE; info->action = info->rule_action->commandType; info->current_varno = rt_index; rt_length = length(parsetree->rtable); /* Adjust rule action and qual to offset its varnos */ info->new_varno = PRS2_NEW_VARNO + rt_length; OffsetVarNodes((Node *) info->rule_action, rt_length, 0); OffsetVarNodes(info->rule_qual, rt_length, 0); /* but its references to *OLD* should point at original rt_index */ ChangeVarNodes((Node *) info->rule_action, PRS2_OLD_VARNO + rt_length, rt_index, 0); ChangeVarNodes(info->rule_qual, PRS2_OLD_VARNO + rt_length, rt_index, 0); /* * We want the main parsetree's rtable to end up as the concatenation * of its original contents plus those of all the relevant rule * actions. Also store same into all the rule_action rtables. * Some of the entries may be unused after we finish rewriting, but * if we tried to clean those out we'd have a much harder job to * adjust RT indexes in the query's Vars. It's OK to have unused * RT entries, since planner will ignore them. * * NOTE KLUGY HACK: we assume the parsetree rtable had at least one * entry to begin with (OK enough, else where'd the rule come from?). * Because of this, if multiple rules nconc() their rtable additions * onto parsetree->rtable, they'll all see the same rtable because * they all have the same list head pointer. */ parsetree->rtable = nconc(parsetree->rtable, info->rule_action->rtable); info->rule_action->rtable = parsetree->rtable; /* * Each rule action's jointree should be the main parsetree's jointree * plus that rule's jointree, but *without* the original rtindex * that we're replacing (if present, which it won't be for INSERT). * Note that if the rule refers to OLD, its jointree will add back * a reference to rt_index. */ { bool found; List *newjointree = adjustJoinTreeList(parsetree, rt_index, &found); info->rule_action->jointree->fromlist = nconc(newjointree, info->rule_action->jointree->fromlist); } /* * bug here about replace CURRENT -- sort of replace current is * deprecated now so this code shouldn't really need to be so * clutzy but..... */ if (info->action != CMD_SELECT) { /* i.e update XXXXX */ int result_reln; int new_result_reln; result_reln = info->rule_action->resultRelation; switch (result_reln) { case PRS2_OLD_VARNO: new_result_reln = rt_index; break; case PRS2_NEW_VARNO: /* XXX */ default: new_result_reln = result_reln + rt_length; break; } info->rule_action->resultRelation = new_result_reln; } } return info; } /* * Copy the query's jointree list, and attempt to remove any occurrence * of the given rt_index as a top-level join item (we do not look for it * within join items; this is OK because we are only expecting to find it * as an UPDATE or DELETE target relation, which will be at the top level * of the join). Returns modified jointree list --- original list * is not changed. *found is set to indicate if we found the rt_index. */ static List * adjustJoinTreeList(Query *parsetree, int rt_index, bool *found) { List *newjointree = listCopy(parsetree->jointree->fromlist); List *jjt; *found = false; foreach(jjt, newjointree) { RangeTblRef *rtr = lfirst(jjt); if (IsA(rtr, RangeTblRef) && rtr->rtindex == rt_index) { newjointree = lremove(rtr, newjointree); *found = true; break; } } return newjointree; } /* * matchLocks - * match the list of locks and returns the matching rules */ static List * matchLocks(CmdType event, RuleLock *rulelocks, int varno, Query *parsetree) { List *real_locks = NIL; int nlocks; int i; Assert(rulelocks != NULL); /* we get called iff there is some lock */ Assert(parsetree != NULL); if (parsetree->commandType != CMD_SELECT) { if (parsetree->resultRelation != varno) return NIL; } nlocks = rulelocks->numLocks; for (i = 0; i < nlocks; i++) { RewriteRule *oneLock = rulelocks->rules[i]; if (oneLock->event == event) { if (parsetree->commandType != CMD_SELECT || (oneLock->attrno == -1 ? rangeTableEntry_used((Node *) parsetree, varno, 0) : attribute_used((Node *) parsetree, varno, oneLock->attrno, 0))) real_locks = lappend(real_locks, oneLock); } } return real_locks; } static Query * ApplyRetrieveRule(Query *parsetree, RewriteRule *rule, int rt_index, bool relation_level, Relation relation, bool relIsUsed) { Query *rule_action; RangeTblEntry *rte, *subrte; List *l; if (length(rule->actions) != 1) elog(ERROR, "ApplyRetrieveRule: expected just one rule action"); if (rule->qual != NULL) elog(ERROR, "ApplyRetrieveRule: can't handle qualified ON SELECT rule"); if (! relation_level) elog(ERROR, "ApplyRetrieveRule: can't handle per-attribute ON SELECT rule"); /* * Make a modifiable copy of the view query, and recursively expand * any view references inside it. */ rule_action = copyObject(lfirst(rule->actions)); rule_action = fireRIRrules(rule_action); /* * VIEWs are really easy --- just plug the view query in as a subselect, * replacing the relation's original RTE. */ rte = rt_fetch(rt_index, parsetree->rtable); rte->relname = NULL; rte->relid = InvalidOid; rte->subquery = rule_action; rte->inh = false; /* must not be set for a subquery */ /* * We move the view's permission check data down to its rangetable. * The checks will actually be done against the *OLD* entry therein. */ subrte = rt_fetch(PRS2_OLD_VARNO, rule_action->rtable); Assert(subrte->relid == relation->rd_id); subrte->checkForRead = rte->checkForRead; subrte->checkForWrite = rte->checkForWrite; rte->checkForRead = false; /* no permission check on subquery itself */ rte->checkForWrite = false; /* * FOR UPDATE of view? */ if (intMember(rt_index, parsetree->rowMarks)) { Index innerrti = 1; CheckSelectForUpdate(rule_action); /* * Remove the view from the list of rels that will actually be * marked FOR UPDATE by the executor. It will still be access- * checked for write access, though. */ parsetree->rowMarks = lremovei(rt_index, parsetree->rowMarks); /* * Set up the view's referenced tables as if FOR UPDATE. */ foreach(l, rule_action->rtable) { subrte = (RangeTblEntry *) lfirst(l); /* * RTable of VIEW has two entries of VIEW itself - skip them! * Also keep hands off of sub-subqueries. */ if (innerrti != PRS2_OLD_VARNO && innerrti != PRS2_NEW_VARNO && subrte->relid != InvalidOid) { if (!intMember(innerrti, rule_action->rowMarks)) rule_action->rowMarks = lappendi(rule_action->rowMarks, innerrti); subrte->checkForWrite = true; } innerrti++; } } return parsetree; } /* * fireRIRonSubLink - * Apply fireRIRrules() to each SubLink (subselect in expression) found * in the given tree. * * NOTE: although this has the form of a walker, we cheat and modify the * SubLink nodes in-place. It is caller's responsibility to ensure that * no unwanted side-effects occur! * * This is unlike most of the other routines that recurse into subselects, * because we must take control at the SubLink node in order to replace * the SubLink's subselect link with the possibly-rewritten subquery. */ static bool fireRIRonSubLink(Node *node, void *context) { if (node == NULL) return false; if (IsA(node, SubLink)) { SubLink *sub = (SubLink *) node; /* Do what we came for */ sub->subselect = (Node *) fireRIRrules((Query *) (sub->subselect)); /* Fall through to process lefthand args of SubLink */ } /* * Do NOT recurse into Query nodes, because fireRIRrules already * processed subselects of subselects for us. */ return expression_tree_walker(node, fireRIRonSubLink, (void *) context); } /* * fireRIRrules - * Apply all RIR rules on each rangetable entry in a query */ static Query * fireRIRrules(Query *parsetree) { int rt_index; RangeTblEntry *rte; Relation rel; List *locks; RuleLock *rules; RewriteRule *rule; bool relIsUsed; int i; List *l; /* * don't try to convert this into a foreach loop, because rtable list * can get changed each time through... */ rt_index = 0; while (rt_index < length(parsetree->rtable)) { ++rt_index; rte = rt_fetch(rt_index, parsetree->rtable); /* * A subquery RTE can't have associated rules, so there's nothing * to do to this level of the query, but we must recurse into the * subquery to expand any rule references in it. */ if (rte->subquery) { rte->subquery = fireRIRrules(rte->subquery); continue; } /* * If the table is not referenced in the query, then we ignore it. * This prevents infinite expansion loop due to new rtable entries * inserted by expansion of a rule. A table is referenced if it is * part of the join set (a source table), or is referenced by any * Var nodes, or is the result table. */ relIsUsed = rangeTableEntry_used((Node *) parsetree, rt_index, 0); if (!relIsUsed && rt_index != parsetree->resultRelation) continue; rel = heap_openr(rte->relname, AccessShareLock); rules = rel->rd_rules; if (rules == NULL) { heap_close(rel, AccessShareLock); continue; } /* * Collect the RIR rules that we must apply */ locks = NIL; for (i = 0; i < rules->numLocks; i++) { rule = rules->rules[i]; if (rule->event != CMD_SELECT) continue; if (rule->attrno > 0) { /* per-attr rule; do we need it? */ if (!attribute_used((Node *) parsetree, rt_index, rule->attrno, 0)) continue; } locks = lappend(locks, rule); } /* * Now apply them */ foreach(l, locks) { rule = lfirst(l); parsetree = ApplyRetrieveRule(parsetree, rule, rt_index, rule->attrno == -1, rel, relIsUsed); } heap_close(rel, AccessShareLock); } /* * Recurse into sublink subqueries, too. */ if (parsetree->hasSubLinks) query_tree_walker(parsetree, fireRIRonSubLink, NULL); /* * If the query was marked having aggregates, check if this is * still true after rewriting. Ditto for sublinks. Note there * should be no aggs in the qual at this point. (Does this code * still do anything useful? The view-becomes-subselect-in-FROM * approach doesn't look like it could remove aggs or sublinks...) */ if (parsetree->hasAggs) { parsetree->hasAggs = checkExprHasAggs((Node *) parsetree); if (parsetree->hasAggs) if (checkExprHasAggs((Node *) parsetree->jointree)) elog(ERROR, "fireRIRrules: failed to remove aggs from qual"); } if (parsetree->hasSubLinks) { parsetree->hasSubLinks = checkExprHasSubLink((Node *) parsetree); } return parsetree; } /* * idea is to fire regular rules first, then qualified instead * rules and unqualified instead rules last. Any lemming is counted for. */ static List * orderRules(List *locks) { List *regular = NIL; List *instead_rules = NIL; List *instead_qualified = NIL; List *i; foreach(i, locks) { RewriteRule *rule_lock = (RewriteRule *) lfirst(i); if (rule_lock->isInstead) { if (rule_lock->qual == NULL) instead_rules = lappend(instead_rules, rule_lock); else instead_qualified = lappend(instead_qualified, rule_lock); } else regular = lappend(regular, rule_lock); } return nconc(nconc(regular, instead_qualified), instead_rules); } static Query * CopyAndAddQual(Query *parsetree, List *actions, Node *rule_qual, int rt_index, CmdType event) { Query *new_tree = (Query *) copyObject(parsetree); Node *new_qual = NULL; Query *rule_action = NULL; if (actions) rule_action = lfirst(actions); if (rule_qual != NULL) new_qual = (Node *) copyObject(rule_qual); if (rule_action != NULL) { List *rtable; int rt_length; List *jointreelist; rtable = new_tree->rtable; rt_length = length(rtable); rtable = nconc(rtable, copyObject(rule_action->rtable)); new_tree->rtable = rtable; OffsetVarNodes(new_qual, rt_length, 0); ChangeVarNodes(new_qual, PRS2_OLD_VARNO + rt_length, rt_index, 0); jointreelist = copyObject(rule_action->jointree->fromlist); OffsetVarNodes((Node *) jointreelist, rt_length, 0); ChangeVarNodes((Node *) jointreelist, PRS2_OLD_VARNO + rt_length, rt_index, 0); new_tree->jointree->fromlist = nconc(new_tree->jointree->fromlist, jointreelist); } /* XXX -- where current doesn't work for instead nothing.... yet */ AddNotQual(new_tree, new_qual); return new_tree; } /* * fireRules - * Iterate through rule locks applying rules. * All rules create their own parsetrees. Instead rules * with rule qualification save the original parsetree * and add their negated qualification to it. Real instead * rules finally throw away the original parsetree. * * remember: reality is for dead birds -- glass * */ static List * fireRules(Query *parsetree, int rt_index, CmdType event, bool *instead_flag, List *locks, List **qual_products) { RewriteInfo *info; List *results = NIL; List *i; /* choose rule to fire from list of rules */ if (locks == NIL) return NIL; locks = orderRules(locks); /* real instead rules last */ foreach(i, locks) { RewriteRule *rule_lock = (RewriteRule *) lfirst(i); Node *event_qual; List *actions; List *r; /* multiple rule action time */ *instead_flag = rule_lock->isInstead; event_qual = rule_lock->qual; actions = rule_lock->actions; if (event_qual != NULL && *instead_flag) { Query *qual_product; RewriteInfo qual_info; /* ---------- * If there are instead rules with qualifications, * the original query is still performed. But all * the negated rule qualifications of the instead * rules are added so it does its actions only * in cases where the rule quals of all instead * rules are false. Think of it as the default * action in a case. We save this in *qual_products * so deepRewriteQuery() can add it to the query * list after we mangled it up enough. * ---------- */ if (*qual_products == NIL) qual_product = parsetree; else qual_product = (Query *) lfirst(*qual_products); MemSet(&qual_info, 0, sizeof(qual_info)); qual_info.event = qual_product->commandType; qual_info.current_varno = rt_index; qual_info.new_varno = length(qual_product->rtable) + 2; qual_product = CopyAndAddQual(qual_product, actions, event_qual, rt_index, event); qual_info.rule_action = qual_product; if (event == CMD_INSERT || event == CMD_UPDATE) FixNew(&qual_info, qual_product); *qual_products = makeList1(qual_product); } foreach(r, actions) { Query *rule_action = lfirst(r); Node *rule_qual = copyObject(event_qual); if (rule_action->commandType == CMD_NOTHING) continue; /*-------------------------------------------------- * We copy the qualifications of the parsetree * to the action and vice versa. So force * hasSubLinks if one of them has it. * * As of 6.4 only parsetree qualifications can * have sublinks. If this changes, we must make * this a node lookup at the end of rewriting. * * Jan *-------------------------------------------------- */ if (parsetree->hasSubLinks && !rule_action->hasSubLinks) { rule_action = copyObject(rule_action); rule_action->hasSubLinks = TRUE; } if (!parsetree->hasSubLinks && rule_action->hasSubLinks) parsetree->hasSubLinks = TRUE; /*-------------------------------------------------- * Step 1: * Rewrite current.attribute or current to tuple variable * this appears to be done in parser? *-------------------------------------------------- */ info = gatherRewriteMeta(parsetree, rule_action, rule_qual, rt_index, event, *instead_flag); /* handle escapable cases, or those handled by other code */ if (info->nothing) { if (*instead_flag) return NIL; else continue; } if (info->action == info->event && info->event == CMD_SELECT) continue; /* * Event Qualification forces copying of parsetree and * splitting into two queries one w/rule_qual, one w/NOT * rule_qual. Also add user query qual onto rule action */ AddQual(info->rule_action, info->rule_qual); AddQual(info->rule_action, parsetree->jointree->quals); /*-------------------------------------------------- * Step 2: * Rewrite new.attribute w/ right hand side of target-list * entry for appropriate field name in insert/update *-------------------------------------------------- */ if ((info->event == CMD_INSERT) || (info->event == CMD_UPDATE)) FixNew(info, parsetree); /*-------------------------------------------------- * Step 3: * Simplify? hey, no algorithm for simplification... let * the planner do it. *-------------------------------------------------- */ results = lappend(results, info->rule_action); pfree(info); } /* ---------- * If this was an unqualified instead rule, * throw away an eventually saved 'default' parsetree * ---------- */ if (event_qual == NULL && *instead_flag) *qual_products = NIL; } return results; } static List * RewriteQuery(Query *parsetree, bool *instead_flag, List **qual_products) { CmdType event; List *product_queries = NIL; int result_relation; RangeTblEntry *rt_entry; Relation rt_entry_relation; RuleLock *rt_entry_locks; Assert(parsetree != NULL); event = parsetree->commandType; /* * SELECT rules are handled later when we have all the queries that * should get executed */ if (event == CMD_SELECT) return NIL; /* * Utilities aren't rewritten at all - why is this here? */ if (event == CMD_UTILITY) return NIL; /* * the statement is an update, insert or delete - fire rules on it. */ result_relation = parsetree->resultRelation; rt_entry = rt_fetch(result_relation, parsetree->rtable); rt_entry_relation = heap_openr(rt_entry->relname, AccessShareLock); rt_entry_locks = rt_entry_relation->rd_rules; if (rt_entry_locks != NULL) { List *locks = matchLocks(event, rt_entry_locks, result_relation, parsetree); product_queries = fireRules(parsetree, result_relation, event, instead_flag, locks, qual_products); } heap_close(rt_entry_relation, AccessShareLock); return product_queries; } /* * to avoid infinite recursion, we restrict the number of times a query * can be rewritten. Detecting cycles is left for the reader as an exercise. */ #ifndef REWRITE_INVOKE_MAX #define REWRITE_INVOKE_MAX 10 #endif static int numQueryRewriteInvoked = 0; /* * deepRewriteQuery - * rewrites the query and apply the rules again on the queries rewritten */ static List * deepRewriteQuery(Query *parsetree) { List *n; List *rewritten = NIL; List *result; bool instead; List *qual_products = NIL; if (++numQueryRewriteInvoked > REWRITE_INVOKE_MAX) { elog(ERROR, "query rewritten %d times, may contain cycles", numQueryRewriteInvoked - 1); } instead = FALSE; result = RewriteQuery(parsetree, &instead, &qual_products); foreach(n, result) { Query *pt = lfirst(n); List *newstuff; newstuff = deepRewriteQuery(pt); if (newstuff != NIL) rewritten = nconc(rewritten, newstuff); } /* ---------- * qual_products are the original query with the negated * rule qualification of an instead rule * ---------- */ if (qual_products != NIL) rewritten = nconc(rewritten, qual_products); /* ---------- * The original query is appended last (if no "instead" rule) * because update and delete rule actions might not do * anything if they are invoked after the update or * delete is performed. The command counter increment * between the query execution makes the deleted (and * maybe the updated) tuples disappear so the scans * for them in the rule actions cannot find them. * ---------- */ if (!instead) rewritten = lappend(rewritten, parsetree); return rewritten; } /* * QueryOneRewrite - * rewrite one query */ static List * QueryRewriteOne(Query *parsetree) { numQueryRewriteInvoked = 0; /* * take a deep breath and apply all the rewrite rules - ay */ return deepRewriteQuery(parsetree); } /* * BasicQueryRewrite - * rewrite one query via query rewrite system, possibly returning 0 * or many queries */ static List * BasicQueryRewrite(Query *parsetree) { List *querylist; List *results = NIL; List *l; Query *query; /* * Step 1 * * Apply all non-SELECT rules possibly getting 0 or many queries */ querylist = QueryRewriteOne(parsetree); /* * Step 2 * * Apply all the RIR rules on each query */ foreach(l, querylist) { query = fireRIRrules((Query *) lfirst(l)); results = lappend(results, query); } return results; } /* * QueryRewrite - * Primary entry point to the query rewriter. * Rewrite one query via query rewrite system, possibly returning 0 * or many queries. * * NOTE: The code in QueryRewrite was formerly in pg_parse_and_plan(), and was * moved here so that it would be invoked during EXPLAIN. The division of * labor between this routine and BasicQueryRewrite is not obviously correct * ... at least not to me ... tgl 5/99. */ List * QueryRewrite(Query *parsetree) { List *rewritten, *rewritten_item; /* * Rewrite Union, Intersect and Except Queries to normal Union Queries * using IN and NOT IN subselects */ if (parsetree->intersectClause) parsetree = Except_Intersect_Rewrite(parsetree); /* Rewrite basic queries (retrieve, append, delete, replace) */ rewritten = BasicQueryRewrite(parsetree); /* * Rewrite the UNIONS. */ foreach(rewritten_item, rewritten) { Query *qry = (Query *) lfirst(rewritten_item); List *union_result = NIL; List *union_item; foreach(union_item, qry->unionClause) { union_result = nconc(union_result, BasicQueryRewrite((Query *) lfirst(union_item))); } qry->unionClause = union_result; } return rewritten; } /* This function takes two targetlists as arguments and checks if the * targetlists are compatible (i.e. both select for the same number of * attributes and the types are compatible */ static void check_targetlists_are_compatible(List *prev_target, List *current_target) { List *tl; int prev_len = 0, next_len = 0; foreach(tl, prev_target) if (!((TargetEntry *) lfirst(tl))->resdom->resjunk) prev_len++; foreach(tl, current_target) if (!((TargetEntry *) lfirst(tl))->resdom->resjunk) next_len++; if (prev_len != next_len) elog(ERROR, "Each UNION | EXCEPT | INTERSECT query must have the same number of columns."); foreach(tl, current_target) { TargetEntry *next_tle = (TargetEntry *) lfirst(tl); TargetEntry *prev_tle; Oid itype; Oid otype; if (next_tle->resdom->resjunk) continue; /* This loop must find an entry, since we counted them above. */ do { prev_tle = (TargetEntry *) lfirst(prev_target); prev_target = lnext(prev_target); } while (prev_tle->resdom->resjunk); itype = next_tle->resdom->restype; otype = prev_tle->resdom->restype; /* one or both is a NULL column? then don't convert... */ if (otype == InvalidOid) { /* propagate a known type forward, if available */ if (itype != InvalidOid) prev_tle->resdom->restype = itype; #ifdef NOT_USED else { prev_tle->resdom->restype = UNKNOWNOID; next_tle->resdom->restype = UNKNOWNOID; } #endif } else if (itype == InvalidOid) { } /* they don't match in type? then convert... */ else if (itype != otype) { Node *expr; expr = next_tle->expr; expr = CoerceTargetExpr(NULL, expr, itype, otype, -1); if (expr == NULL) { elog(ERROR, "Unable to transform %s to %s" "\n\tEach UNION | EXCEPT | INTERSECT clause must have compatible target types", typeidTypeName(itype), typeidTypeName(otype)); } next_tle->expr = expr; next_tle->resdom->restype = otype; } /* both are UNKNOWN? then evaluate as text... */ else if (itype == UNKNOWNOID) { next_tle->resdom->restype = TEXTOID; prev_tle->resdom->restype = TEXTOID; } } } /* * Rewrites UNION INTERSECT and EXCEPT queries to semantically equivalent * queries that use IN and NOT IN subselects. * * The operator tree is attached to 'intersectClause' (see rule * 'SelectStmt' in gram.y) of the 'parsetree' given as an * argument. First we remember some clauses (the sortClause, the * distinctClause etc.) Then we translate the operator tree to DNF * (disjunctive normal form) by 'cnfify'. (Note that 'cnfify' produces * CNF but as we exchanged ANDs with ORs in function A_Expr_to_Expr() * earlier we get DNF after exchanging ANDs and ORs again in the * result.) Now we create a new query by evaluating the new operator * tree which is in DNF now. For every AND we create an entry in the * union list and for every OR we create an IN subselect. (NOT IN * subselects are created for OR NOT nodes). The first entry of the * union list is handed back but before that the remembered clauses * (sortClause etc) are attached to the new top Node (Note that the * new top Node can differ from the parsetree given as argument because of * the translation to DNF. That's why we have to remember the sortClause * and so on!) */ static Query * Except_Intersect_Rewrite(Query *parsetree) { SubLink *n; Query *result, *intersect_node; List *elist, *intersect_list = NIL, *intersect, *intersectClause; List *union_list = NIL, *sortClause, *distinctClause; List *left_expr, *resnames = NIL; char *op, *into; bool isBinary, isPortal, isTemp; Node *limitOffset, *limitCount; CmdType commandType = CMD_SELECT; RangeTblEntry *rtable_insert = NULL; List *prev_target = NIL; /* * Remember the Resnames of the given parsetree's targetlist (these * are the resnames of the first Select Statement of the query * formulated by the user and he wants the columns named by these * strings. The transformation to DNF can cause another Select * Statment to be the top one which uses other names for its columns. * Therefore we remember the original names and attach them to the * targetlist of the new topmost Node at the end of this function */ foreach(elist, parsetree->targetList) { TargetEntry *tent = (TargetEntry *) lfirst(elist); if (! tent->resdom->resjunk) resnames = lappend(resnames, tent->resdom->resname); } /* * If the Statement is an INSERT INTO ... (SELECT...) statement using * UNIONs, INTERSECTs or EXCEPTs and the transformation to DNF makes * another Node to the top node we have to transform the new top node * to an INSERT node and the original INSERT node to a SELECT node */ if (parsetree->commandType == CMD_INSERT) { /* * The result relation ( = the one to insert into) has to be * attached to the rtable list of the new top node */ rtable_insert = rt_fetch(parsetree->resultRelation, parsetree->rtable); parsetree->commandType = CMD_SELECT; commandType = CMD_INSERT; parsetree->resultRelation = 0; } /* * Save some items, to be able to attach them to the resulting top * node at the end of the function */ sortClause = parsetree->sortClause; distinctClause = parsetree->distinctClause; into = parsetree->into; isBinary = parsetree->isBinary; isPortal = parsetree->isPortal; isTemp = parsetree->isTemp; limitOffset = parsetree->limitOffset; limitCount = parsetree->limitCount; /* * The operator tree attached to parsetree->intersectClause is still * 'raw' ( = the leaf nodes are still SelectStmt nodes instead of * Query nodes) So step through the tree and transform the nodes using * parse_analyze(). * * The parsetree (given as an argument to Except_Intersect_Rewrite()) has * already been transformed and transforming it again would cause * troubles. So we give the 'raw' version (of the cooked parsetree) * to the function to prevent an additional transformation. Instead we * hand back the 'cooked' version also given as an argument to * intersect_tree_analyze() */ intersectClause = (List *) intersect_tree_analyze((Node *) parsetree->intersectClause, (Node *) lfirst(parsetree->unionClause), (Node *) parsetree); /* intersectClause is no longer needed so set it to NIL */ parsetree->intersectClause = NIL; /* * unionClause will be needed later on but the list it delivered is no * longer needed, so set it to NIL */ parsetree->unionClause = NIL; /* * Transform the operator tree to DNF (remember ANDs and ORs have been * exchanged, that's why we get DNF by using cnfify) * * After the call, explicit ANDs are removed and all AND operands are * simply items in the intersectClause list */ intersectClause = cnfify((Expr *) intersectClause, true); /* * For every entry of the intersectClause list we generate one entry * in the union_list */ foreach(intersect, intersectClause) { /* * for every OR we create an IN subselect and for every OR NOT we * create a NOT IN subselect, so first extract all the Select * Query nodes from the tree (that contains only OR or OR NOTs any * more because we did a transformation to DNF * * There must be at least one node that is not negated (i.e. just OR * and not OR NOT) and this node will be the first in the list * returned */ intersect_list = NIL; create_intersect_list((Node *) lfirst(intersect), &intersect_list); /* * This one will become the Select Query node, all other nodes are * transformed into subselects under this node! */ intersect_node = (Query *) lfirst(intersect_list); intersect_list = lnext(intersect_list); /* * Check if all Select Statements use the same number of * attributes and if all corresponding attributes are of the same * type */ if (prev_target) check_targetlists_are_compatible(prev_target, intersect_node->targetList); prev_target = intersect_node->targetList; /* * Transform all nodes remaining into subselects and add them to * the qualifications of the Select Query node */ while (intersect_list != NIL) { n = makeNode(SubLink); /* Here we got an OR so transform it to an IN subselect */ if (IsA(lfirst(intersect_list), Query)) { /* * Check if all Select Statements use the same number of * attributes and if all corresponding attributes are of * the same type */ check_targetlists_are_compatible(prev_target, ((Query *) lfirst(intersect_list))->targetList); n->subselect = lfirst(intersect_list); op = "="; n->subLinkType = ANY_SUBLINK; n->useor = false; } /* * Here we got an OR NOT node so transform it to a NOT IN * subselect */ else { /* * Check if all Select Statements use the same number of * attributes and if all corresponding attributes are of * the same type */ check_targetlists_are_compatible(prev_target, ((Query *) lfirst(((Expr *) lfirst(intersect_list))->args))->targetList); n->subselect = (Node *) lfirst(((Expr *) lfirst(intersect_list))->args); op = "<>"; n->subLinkType = ALL_SUBLINK; n->useor = true; } /* * Prepare the lefthand side of the Sublinks: All the entries * of the targetlist must be (IN) or must not be (NOT IN) the * subselect */ n->lefthand = NIL; foreach(elist, intersect_node->targetList) { TargetEntry *tent = (TargetEntry *) lfirst(elist); if (! tent->resdom->resjunk) n->lefthand = lappend(n->lefthand, tent->expr); } /* * Also prepare the list of Opers that must be used for the * comparisons (they depend on the specific datatypes * involved!) */ left_expr = n->lefthand; n->oper = NIL; foreach(elist, ((Query *) (n->subselect))->targetList) { TargetEntry *tent = (TargetEntry *) lfirst(elist); Node *lexpr; Operator optup; Form_pg_operator opform; Oper *newop; if (tent->resdom->resjunk) continue; lexpr = lfirst(left_expr); optup = oper(op, exprType(lexpr), exprType(tent->expr), FALSE); opform = (Form_pg_operator) GETSTRUCT(optup); if (opform->oprresult != BOOLOID) elog(ERROR, "parser: '%s' must return 'bool' to be used with quantified predicate subquery", op); newop = makeOper(oprid(optup), /* opno */ InvalidOid, /* opid */ opform->oprresult); n->oper = lappend(n->oper, newop); left_expr = lnext(left_expr); } Assert(left_expr == NIL); /* should have used 'em all */ /* * If the Select Query node has aggregates in use add all the * subselects to the HAVING qual else to the WHERE qual */ if (intersect_node->hasAggs) AddHavingQual(intersect_node, (Node *) n); else AddQual(intersect_node, (Node *) n); /* Now we got sublinks */ intersect_node->hasSubLinks = true; intersect_list = lnext(intersect_list); } intersect_node->intersectClause = NIL; union_list = lappend(union_list, intersect_node); } /* The first entry to union_list is our new top node */ result = (Query *) lfirst(union_list); /* attach the rest to unionClause */ result->unionClause = lnext(union_list); /* Attach all the items remembered in the beginning of the function */ result->sortClause = sortClause; result->distinctClause = distinctClause; result->into = into; result->isPortal = isPortal; result->isBinary = isBinary; result->isTemp = isTemp; result->limitOffset = limitOffset; result->limitCount = limitCount; /* * The relation to insert into is attached to the range table of the * new top node */ if (commandType == CMD_INSERT) { result->rtable = lappend(result->rtable, rtable_insert); result->resultRelation = length(result->rtable); result->commandType = commandType; } /* * The resnames of the originally first SelectStatement are attached * to the new first SelectStatement */ foreach(elist, result->targetList) { TargetEntry *tent = (TargetEntry *) lfirst(elist); if (tent->resdom->resjunk) continue; tent->resdom->resname = lfirst(resnames); resnames = lnext(resnames); } return result; } /* * Create a list of nodes that are either Query nodes of NOT Expr * nodes followed by a Query node. The tree given in ptr contains at * least one non negated Query node. This node is attached to the * beginning of the list. */ static void create_intersect_list(Node *ptr, List **intersect_list) { List *arg; if (IsA(ptr, Query)) { /* The non negated node is attached at the beginning (lcons) */ *intersect_list = lcons(ptr, *intersect_list); return; } if (IsA(ptr, Expr)) { if (((Expr *) ptr)->opType == NOT_EXPR) { /* negated nodes are appended to the end (lappend) */ *intersect_list = lappend(*intersect_list, ptr); return; } else { foreach(arg, ((Expr *) ptr)->args) create_intersect_list(lfirst(arg), intersect_list); return; } return; } } /* * The nodes given in 'tree' are still 'raw' so 'cook' them using * parse_analyze(). The node given in first_select has already been cooked, * so don't transform it again but return a pointer to the previously cooked * version given in 'parsetree' instead. */ static Node * intersect_tree_analyze(Node *tree, Node *first_select, Node *parsetree) { Node *result = (Node *) NIL; List *arg; if (IsA(tree, SelectStmt)) { /* * If we get to the tree given in first_select return parsetree * instead of performing parse_analyze() */ if (tree == first_select) result = parsetree; else { /* transform the 'raw' nodes to 'cooked' Query nodes */ List *qtree = parse_analyze(makeList1(tree), NULL); result = (Node *) lfirst(qtree); } } if (IsA(tree, Expr)) { /* Call recursively for every argument of the node */ foreach(arg, ((Expr *) tree)->args) lfirst(arg) = intersect_tree_analyze(lfirst(arg), first_select, parsetree); result = tree; } return result; }