/*------------------------------------------------------------------------- * * rewriteHandler.c * Primary module of query rewriter. * * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/rewrite/rewriteHandler.c,v 1.165 2006/08/02 01:59:47 joe Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "catalog/pg_type.h" #include "nodes/makefuncs.h" #include "optimizer/clauses.h" #include "parser/analyze.h" #include "parser/parse_coerce.h" #include "parser/parse_expr.h" #include "parser/parsetree.h" #include "rewrite/rewriteHandler.h" #include "rewrite/rewriteManip.h" #include "utils/builtins.h" #include "utils/lsyscache.h" /* We use a list of these to detect recursion in RewriteQuery */ typedef struct rewrite_event { Oid relation; /* OID of relation having rules */ CmdType event; /* type of rule being fired */ } rewrite_event; static bool acquireLocksOnSubLinks(Node *node, void *context); static Query *rewriteRuleAction(Query *parsetree, Query *rule_action, Node *rule_qual, int rt_index, CmdType event); static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index); static void rewriteTargetList(Query *parsetree, Relation target_relation, List **attrno_list); static TargetEntry *process_matched_tle(TargetEntry *src_tle, TargetEntry *prior_tle, const char *attrName); static Node *get_assignment_input(Node *node); static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos); static void markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew); static List *matchLocks(CmdType event, RuleLock *rulelocks, int varno, Query *parsetree); static Query *fireRIRrules(Query *parsetree, List *activeRIRs); /* * AcquireRewriteLocks - * Acquire suitable locks on all the relations mentioned in the Query. * These locks will ensure that the relation schemas don't change under us * while we are rewriting and planning the query. * * A secondary purpose of this routine is to fix up JOIN RTE references to * dropped columns (see details below). Because the RTEs are modified in * place, it is generally appropriate for the caller of this routine to have * first done a copyObject() to make a writable copy of the querytree in the * current memory context. * * This processing can, and for efficiency's sake should, be skipped when the * querytree has just been built by the parser: parse analysis already got * all the same locks we'd get here, and the parser will have omitted dropped * columns from JOINs to begin with. But we must do this whenever we are * dealing with a querytree produced earlier than the current command. * * About JOINs and dropped columns: although the parser never includes an * already-dropped column in a JOIN RTE's alias var list, it is possible for * such a list in a stored rule to include references to dropped columns. * (If the column is not explicitly referenced anywhere else in the query, * the dependency mechanism won't consider it used by the rule and so won't * prevent the column drop.) To support get_rte_attribute_is_dropped(), * we replace join alias vars that reference dropped columns with NULL Const * nodes. * * (In PostgreSQL 8.0, we did not do this processing but instead had * get_rte_attribute_is_dropped() recurse to detect dropped columns in joins. * That approach had horrible performance unfortunately; in particular * construction of a nested join was O(N^2) in the nesting depth.) */ void AcquireRewriteLocks(Query *parsetree) { ListCell *l; int rt_index; /* * First, process RTEs of the current query level. */ rt_index = 0; foreach(l, parsetree->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(l); Relation rel; LOCKMODE lockmode; List *newaliasvars; Index curinputvarno; RangeTblEntry *curinputrte; ListCell *ll; ++rt_index; switch (rte->rtekind) { case RTE_RELATION: /* * Grab the appropriate lock type for the relation, and do not * release it until end of transaction. This protects the * rewriter and planner against schema changes mid-query. * * If the relation is the query's result relation, then we * need RowExclusiveLock. Otherwise, check to see if the * relation is accessed FOR UPDATE/SHARE or not. We can't * just grab AccessShareLock because then the executor would * be trying to upgrade the lock, leading to possible * deadlocks. */ if (rt_index == parsetree->resultRelation) lockmode = RowExclusiveLock; else if (get_rowmark(parsetree, rt_index)) lockmode = RowShareLock; else lockmode = AccessShareLock; rel = heap_open(rte->relid, lockmode); heap_close(rel, NoLock); break; case RTE_JOIN: /* * Scan the join's alias var list to see if any columns have * been dropped, and if so replace those Vars with NULL * Consts. * * Since a join has only two inputs, we can expect to see * multiple references to the same input RTE; optimize away * multiple fetches. */ newaliasvars = NIL; curinputvarno = 0; curinputrte = NULL; foreach(ll, rte->joinaliasvars) { Var *aliasvar = (Var *) lfirst(ll); /* * If the list item isn't a simple Var, then it must * represent a merged column, ie a USING column, and so it * couldn't possibly be dropped, since it's referenced in * the join clause. (Conceivably it could also be a NULL * constant already? But that's OK too.) */ if (IsA(aliasvar, Var)) { /* * The elements of an alias list have to refer to * earlier RTEs of the same rtable, because that's the * order the planner builds things in. So we already * processed the referenced RTE, and so it's safe to * use get_rte_attribute_is_dropped on it. (This might * not hold after rewriting or planning, but it's OK * to assume here.) */ Assert(aliasvar->varlevelsup == 0); if (aliasvar->varno != curinputvarno) { curinputvarno = aliasvar->varno; if (curinputvarno >= rt_index) elog(ERROR, "unexpected varno %d in JOIN RTE %d", curinputvarno, rt_index); curinputrte = rt_fetch(curinputvarno, parsetree->rtable); } if (get_rte_attribute_is_dropped(curinputrte, aliasvar->varattno)) { /* * can't use vartype here, since that might be a * now-dropped type OID, but it doesn't really * matter what type the Const claims to be. */ aliasvar = (Var *) makeNullConst(INT4OID); } } newaliasvars = lappend(newaliasvars, aliasvar); } rte->joinaliasvars = newaliasvars; break; case RTE_SUBQUERY: /* * The subquery RTE itself is all right, but we have to * recurse to process the represented subquery. */ AcquireRewriteLocks(rte->subquery); break; default: /* ignore other types of RTEs */ break; } } /* * Recurse into sublink subqueries, too. But we already did the ones in * the rtable. */ if (parsetree->hasSubLinks) query_tree_walker(parsetree, acquireLocksOnSubLinks, NULL, QTW_IGNORE_RT_SUBQUERIES); } /* * Walker to find sublink subqueries for AcquireRewriteLocks */ static bool acquireLocksOnSubLinks(Node *node, void *context) { if (node == NULL) return false; if (IsA(node, SubLink)) { SubLink *sub = (SubLink *) node; /* Do what we came for */ AcquireRewriteLocks((Query *) sub->subselect); /* Fall through to process lefthand args of SubLink */ } /* * Do NOT recurse into Query nodes, because AcquireRewriteLocks already * processed subselects of subselects for us. */ return expression_tree_walker(node, acquireLocksOnSubLinks, context); } /* * rewriteRuleAction - * Rewrite the rule action with appropriate qualifiers (taken from * the triggering query). */ static Query * rewriteRuleAction(Query *parsetree, Query *rule_action, Node *rule_qual, int rt_index, CmdType event) { int current_varno, new_varno; int rt_length; Query *sub_action; Query **sub_action_ptr; /* * Make modifiable copies of rule action and qual (what we're passed are * the stored versions in the relcache; don't touch 'em!). */ rule_action = (Query *) copyObject(rule_action); rule_qual = (Node *) copyObject(rule_qual); /* * Acquire necessary locks and fix any deleted JOIN RTE entries. */ AcquireRewriteLocks(rule_action); (void) acquireLocksOnSubLinks(rule_qual, NULL); current_varno = rt_index; rt_length = list_length(parsetree->rtable); new_varno = PRS2_NEW_VARNO + rt_length; /* * Adjust rule action and qual to offset its varnos, so that we can merge * its rtable with the main parsetree's rtable. * * If the rule action is an INSERT...SELECT, the OLD/NEW rtable entries * will be in the SELECT part, and we have to modify that rather than the * top-level INSERT (kluge!). */ sub_action = getInsertSelectQuery(rule_action, &sub_action_ptr); OffsetVarNodes((Node *) sub_action, rt_length, 0); OffsetVarNodes(rule_qual, rt_length, 0); /* but references to *OLD* should point at original rt_index */ ChangeVarNodes((Node *) sub_action, PRS2_OLD_VARNO + rt_length, rt_index, 0); ChangeVarNodes(rule_qual, PRS2_OLD_VARNO + rt_length, rt_index, 0); /* * Generate expanded rtable consisting of main parsetree's rtable plus * rule action's rtable; this becomes the complete rtable for the rule * action. Some of the entries may be unused after we finish rewriting, * but we leave them all in place for two reasons: * * We'd have a much harder job to adjust the query's varnos if we * selectively removed RT entries. * * If the rule is INSTEAD, then the original query won't be executed at * all, and so its rtable must be preserved so that the executor will do * the correct permissions checks on it. * * RT entries that are not referenced in the completed jointree will be * ignored by the planner, so they do not affect query semantics. But any * permissions checks specified in them will be applied during executor * startup (see ExecCheckRTEPerms()). This allows us to check that the * caller has, say, insert-permission on a view, when the view is not * semantically referenced at all in the resulting query. * * When a rule is not INSTEAD, the permissions checks done on its copied * RT entries will be redundant with those done during execution of the * original query, but we don't bother to treat that case differently. * * NOTE: because planner will destructively alter rtable, we must ensure * that rule action's rtable is separate and shares no substructure with * the main rtable. Hence do a deep copy here. */ sub_action->rtable = list_concat((List *) copyObject(parsetree->rtable), sub_action->rtable); /* * Each rule action's jointree should be the main parsetree's jointree * plus that rule's jointree, but usually *without* the original rtindex * that we're replacing (if present, which it won't be for INSERT). Note * that if the rule action refers to OLD, its jointree will add a * reference to rt_index. If the rule action doesn't refer to OLD, but * either the rule_qual or the user query quals do, then we need to keep * the original rtindex in the jointree to provide data for the quals. We * don't want the original rtindex to be joined twice, however, so avoid * keeping it if the rule action mentions it. * * As above, the action's jointree must not share substructure with the * main parsetree's. */ if (sub_action->commandType != CMD_UTILITY) { bool keeporig; List *newjointree; Assert(sub_action->jointree != NULL); keeporig = (!rangeTableEntry_used((Node *) sub_action->jointree, rt_index, 0)) && (rangeTableEntry_used(rule_qual, rt_index, 0) || rangeTableEntry_used(parsetree->jointree->quals, rt_index, 0)); newjointree = adjustJoinTreeList(parsetree, !keeporig, rt_index); if (newjointree != NIL) { /* * If sub_action is a setop, manipulating its jointree will do no * good at all, because the jointree is dummy. (Perhaps someday * we could push the joining and quals down to the member * statements of the setop?) */ if (sub_action->setOperations != NULL) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("conditional UNION/INTERSECT/EXCEPT statements are not implemented"))); sub_action->jointree->fromlist = list_concat(newjointree, sub_action->jointree->fromlist); /* * There could have been some SubLinks in newjointree, in which * case we'd better mark the sub_action correctly. */ if (parsetree->hasSubLinks && !sub_action->hasSubLinks) sub_action->hasSubLinks = checkExprHasSubLink((Node *) newjointree); } } /* * 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(sub_action, rule_qual); AddQual(sub_action, parsetree->jointree->quals); /* * Rewrite new.attribute w/ right hand side of target-list entry for * appropriate field name in insert/update. * * KLUGE ALERT: since ResolveNew returns a mutated copy, we can't just * apply it to sub_action; we have to remember to update the sublink * inside rule_action, too. */ if ((event == CMD_INSERT || event == CMD_UPDATE) && sub_action->commandType != CMD_UTILITY) { sub_action = (Query *) ResolveNew((Node *) sub_action, new_varno, 0, rt_fetch(new_varno, sub_action->rtable), parsetree->targetList, event, current_varno); if (sub_action_ptr) *sub_action_ptr = sub_action; else rule_action = sub_action; } return rule_action; } /* * Copy the query's jointree list, and optionally 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 --- this is a separate copy * sharing no nodes with the original. */ static List * adjustJoinTreeList(Query *parsetree, bool removert, int rt_index) { List *newjointree = copyObject(parsetree->jointree->fromlist); ListCell *l; if (removert) { foreach(l, newjointree) { RangeTblRef *rtr = lfirst(l); if (IsA(rtr, RangeTblRef) && rtr->rtindex == rt_index) { newjointree = list_delete_ptr(newjointree, rtr); /* * foreach is safe because we exit loop after list_delete... */ break; } } } return newjointree; } /* * rewriteTargetList - rewrite INSERT/UPDATE targetlist into standard form * * This has the following responsibilities: * * 1. For an INSERT, add tlist entries to compute default values for any * attributes that have defaults and are not assigned to in the given tlist. * (We do not insert anything for default-less attributes, however. The * planner will later insert NULLs for them, but there's no reason to slow * down rewriter processing with extra tlist nodes.) Also, for both INSERT * and UPDATE, replace explicit DEFAULT specifications with column default * expressions. * * 2. Merge multiple entries for the same target attribute, or declare error * if we can't. Multiple entries are only allowed for INSERT/UPDATE of * portions of an array or record field, for example * UPDATE table SET foo[2] = 42, foo[4] = 43; * We can merge such operations into a single assignment op. Essentially, * the expression we want to produce in this case is like * foo = array_set(array_set(foo, 2, 42), 4, 43) * * 3. Sort the tlist into standard order: non-junk fields in order by resno, * then junk fields (these in no particular order). * * We must do items 1 and 2 before firing rewrite rules, else rewritten * references to NEW.foo will produce wrong or incomplete results. Item 3 * is not needed for rewriting, but will be needed by the planner, and we * can do it essentially for free while handling items 1 and 2. * * If attrno_list isn't NULL, we return an additional output besides the * rewritten targetlist: an integer list of the assigned-to attnums, in * order of the original tlist's non-junk entries. This is needed for * processing VALUES RTEs. */ static void rewriteTargetList(Query *parsetree, Relation target_relation, List **attrno_list) { CmdType commandType = parsetree->commandType; TargetEntry **new_tles; List *new_tlist = NIL; List *junk_tlist = NIL; Form_pg_attribute att_tup; int attrno, next_junk_attrno, numattrs; ListCell *temp; if (attrno_list) /* initialize optional result list */ *attrno_list = NIL; /* * We process the normal (non-junk) attributes by scanning the input tlist * once and transferring TLEs into an array, then scanning the array to * build an output tlist. This avoids O(N^2) behavior for large numbers * of attributes. * * Junk attributes are tossed into a separate list during the same tlist * scan, then appended to the reconstructed tlist. */ numattrs = RelationGetNumberOfAttributes(target_relation); new_tles = (TargetEntry **) palloc0(numattrs * sizeof(TargetEntry *)); next_junk_attrno = numattrs + 1; foreach(temp, parsetree->targetList) { TargetEntry *old_tle = (TargetEntry *) lfirst(temp); if (!old_tle->resjunk) { /* Normal attr: stash it into new_tles[] */ attrno = old_tle->resno; if (attrno < 1 || attrno > numattrs) elog(ERROR, "bogus resno %d in targetlist", attrno); att_tup = target_relation->rd_att->attrs[attrno - 1]; /* put attrno into attrno_list even if it's dropped */ if (attrno_list) *attrno_list = lappend_int(*attrno_list, attrno); /* We can (and must) ignore deleted attributes */ if (att_tup->attisdropped) continue; /* Merge with any prior assignment to same attribute */ new_tles[attrno - 1] = process_matched_tle(old_tle, new_tles[attrno - 1], NameStr(att_tup->attname)); } else { /* * Copy all resjunk tlist entries to junk_tlist, and assign them * resnos above the last real resno. * * Typical junk entries include ORDER BY or GROUP BY expressions * (are these actually possible in an INSERT or UPDATE?), system * attribute references, etc. */ /* Get the resno right, but don't copy unnecessarily */ if (old_tle->resno != next_junk_attrno) { old_tle = flatCopyTargetEntry(old_tle); old_tle->resno = next_junk_attrno; } junk_tlist = lappend(junk_tlist, old_tle); next_junk_attrno++; } } for (attrno = 1; attrno <= numattrs; attrno++) { TargetEntry *new_tle = new_tles[attrno - 1]; att_tup = target_relation->rd_att->attrs[attrno - 1]; /* We can (and must) ignore deleted attributes */ if (att_tup->attisdropped) continue; /* * Handle the two cases where we need to insert a default expression: * it's an INSERT and there's no tlist entry for the column, or the * tlist entry is a DEFAULT placeholder node. */ if ((new_tle == NULL && commandType == CMD_INSERT) || (new_tle && new_tle->expr && IsA(new_tle->expr, SetToDefault))) { Node *new_expr; new_expr = build_column_default(target_relation, attrno); /* * If there is no default (ie, default is effectively NULL), we * can omit the tlist entry in the INSERT case, since the planner * can insert a NULL for itself, and there's no point in spending * any more rewriter cycles on the entry. But in the UPDATE case * we've got to explicitly set the column to NULL. */ if (!new_expr) { if (commandType == CMD_INSERT) new_tle = NULL; else { new_expr = (Node *) makeConst(att_tup->atttypid, att_tup->attlen, (Datum) 0, true, /* isnull */ att_tup->attbyval); /* this is to catch a NOT NULL domain constraint */ new_expr = coerce_to_domain(new_expr, InvalidOid, -1, att_tup->atttypid, COERCE_IMPLICIT_CAST, false, false); } } if (new_expr) new_tle = makeTargetEntry((Expr *) new_expr, attrno, pstrdup(NameStr(att_tup->attname)), false); } if (new_tle) new_tlist = lappend(new_tlist, new_tle); } pfree(new_tles); parsetree->targetList = list_concat(new_tlist, junk_tlist); } /* * Convert a matched TLE from the original tlist into a correct new TLE. * * This routine detects and handles multiple assignments to the same target * attribute. (The attribute name is needed only for error messages.) */ static TargetEntry * process_matched_tle(TargetEntry *src_tle, TargetEntry *prior_tle, const char *attrName) { TargetEntry *result; Node *src_expr; Node *prior_expr; Node *src_input; Node *prior_input; Node *priorbottom; Node *newexpr; if (prior_tle == NULL) { /* * Normal case where this is the first assignment to the attribute. */ return src_tle; } /*---------- * Multiple assignments to same attribute. Allow only if all are * FieldStore or ArrayRef assignment operations. This is a bit * tricky because what we may actually be looking at is a nest of * such nodes; consider * UPDATE tab SET col.fld1.subfld1 = x, col.fld2.subfld2 = y * The two expressions produced by the parser will look like * FieldStore(col, fld1, FieldStore(placeholder, subfld1, x)) * FieldStore(col, fld2, FieldStore(placeholder, subfld2, x)) * However, we can ignore the substructure and just consider the top * FieldStore or ArrayRef from each assignment, because it works to * combine these as * FieldStore(FieldStore(col, fld1, * FieldStore(placeholder, subfld1, x)), * fld2, FieldStore(placeholder, subfld2, x)) * Note the leftmost expression goes on the inside so that the * assignments appear to occur left-to-right. * * For FieldStore, instead of nesting we can generate a single * FieldStore with multiple target fields. We must nest when * ArrayRefs are involved though. *---------- */ src_expr = (Node *) src_tle->expr; prior_expr = (Node *) prior_tle->expr; src_input = get_assignment_input(src_expr); prior_input = get_assignment_input(prior_expr); if (src_input == NULL || prior_input == NULL || exprType(src_expr) != exprType(prior_expr)) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("multiple assignments to same column \"%s\"", attrName))); /* * Prior TLE could be a nest of assignments if we do this more than once. */ priorbottom = prior_input; for (;;) { Node *newbottom = get_assignment_input(priorbottom); if (newbottom == NULL) break; /* found the original Var reference */ priorbottom = newbottom; } if (!equal(priorbottom, src_input)) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("multiple assignments to same column \"%s\"", attrName))); /* * Looks OK to nest 'em. */ if (IsA(src_expr, FieldStore)) { FieldStore *fstore = makeNode(FieldStore); if (IsA(prior_expr, FieldStore)) { /* combine the two */ memcpy(fstore, prior_expr, sizeof(FieldStore)); fstore->newvals = list_concat(list_copy(((FieldStore *) prior_expr)->newvals), list_copy(((FieldStore *) src_expr)->newvals)); fstore->fieldnums = list_concat(list_copy(((FieldStore *) prior_expr)->fieldnums), list_copy(((FieldStore *) src_expr)->fieldnums)); } else { /* general case, just nest 'em */ memcpy(fstore, src_expr, sizeof(FieldStore)); fstore->arg = (Expr *) prior_expr; } newexpr = (Node *) fstore; } else if (IsA(src_expr, ArrayRef)) { ArrayRef *aref = makeNode(ArrayRef); memcpy(aref, src_expr, sizeof(ArrayRef)); aref->refexpr = (Expr *) prior_expr; newexpr = (Node *) aref; } else { elog(ERROR, "can't happen"); newexpr = NULL; } result = flatCopyTargetEntry(src_tle); result->expr = (Expr *) newexpr; return result; } /* * If node is an assignment node, return its input; else return NULL */ static Node * get_assignment_input(Node *node) { if (node == NULL) return NULL; if (IsA(node, FieldStore)) { FieldStore *fstore = (FieldStore *) node; return (Node *) fstore->arg; } else if (IsA(node, ArrayRef)) { ArrayRef *aref = (ArrayRef *) node; if (aref->refassgnexpr == NULL) return NULL; return (Node *) aref->refexpr; } return NULL; } /* * Make an expression tree for the default value for a column. * * If there is no default, return a NULL instead. */ Node * build_column_default(Relation rel, int attrno) { TupleDesc rd_att = rel->rd_att; Form_pg_attribute att_tup = rd_att->attrs[attrno - 1]; Oid atttype = att_tup->atttypid; int32 atttypmod = att_tup->atttypmod; Node *expr = NULL; Oid exprtype; /* * Scan to see if relation has a default for this column. */ if (rd_att->constr && rd_att->constr->num_defval > 0) { AttrDefault *defval = rd_att->constr->defval; int ndef = rd_att->constr->num_defval; while (--ndef >= 0) { if (attrno == defval[ndef].adnum) { /* * Found it, convert string representation to node tree. */ expr = stringToNode(defval[ndef].adbin); break; } } } if (expr == NULL) { /* * No per-column default, so look for a default for the type itself. */ expr = get_typdefault(atttype); } if (expr == NULL) return NULL; /* No default anywhere */ /* * Make sure the value is coerced to the target column type; this will * generally be true already, but there seem to be some corner cases * involving domain defaults where it might not be true. This should match * the parser's processing of non-defaulted expressions --- see * transformAssignedExpr(). */ exprtype = exprType(expr); expr = coerce_to_target_type(NULL, /* no UNKNOWN params here */ expr, exprtype, atttype, atttypmod, COERCION_ASSIGNMENT, COERCE_IMPLICIT_CAST); if (expr == NULL) ereport(ERROR, (errcode(ERRCODE_DATATYPE_MISMATCH), errmsg("column \"%s\" is of type %s" " but default expression is of type %s", NameStr(att_tup->attname), format_type_be(atttype), format_type_be(exprtype)), errhint("You will need to rewrite or cast the expression."))); return expr; } /* Does VALUES RTE contain any SetToDefault items? */ static bool searchForDefault(RangeTblEntry *rte) { ListCell *lc; foreach(lc, rte->values_lists) { List *sublist = (List *) lfirst(lc); ListCell *lc2; foreach(lc2, sublist) { Node *col = (Node *) lfirst(lc2); if (IsA(col, SetToDefault)) return true; } } return false; } /* * When processing INSERT ... VALUES with a VALUES RTE (ie, multiple VALUES * lists), we have to replace any DEFAULT items in the VALUES lists with * the appropriate default expressions. The other aspects of rewriteTargetList * need be applied only to the query's targetlist proper. * * Note that we currently can't support subscripted or field assignment * in the multi-VALUES case. The targetlist will contain simple Vars * referencing the VALUES RTE, and therefore process_matched_tle() will * reject any such attempt with "multiple assignments to same column". */ static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos) { List *newValues; ListCell *lc; /* * Rebuilding all the lists is a pretty expensive proposition in a big * VALUES list, and it's a waste of time if there aren't any DEFAULT * placeholders. So first scan to see if there are any. */ if (!searchForDefault(rte)) return; /* nothing to do */ /* Check list lengths (we can assume all the VALUES sublists are alike) */ Assert(list_length(attrnos) == list_length(linitial(rte->values_lists))); newValues = NIL; foreach(lc, rte->values_lists) { List *sublist = (List *) lfirst(lc); List *newList = NIL; ListCell *lc2; ListCell *lc3; forboth(lc2, sublist, lc3, attrnos) { Node *col = (Node *) lfirst(lc2); int attrno = lfirst_int(lc3); if (IsA(col, SetToDefault)) { Form_pg_attribute att_tup; Node *new_expr; att_tup = target_relation->rd_att->attrs[attrno - 1]; if (!att_tup->attisdropped) new_expr = build_column_default(target_relation, attrno); else new_expr = NULL; /* force a NULL if dropped */ /* * If there is no default (ie, default is effectively NULL), * we've got to explicitly set the column to NULL. */ if (!new_expr) { new_expr = (Node *) makeConst(att_tup->atttypid, att_tup->attlen, (Datum) 0, true, /* isnull */ att_tup->attbyval); /* this is to catch a NOT NULL domain constraint */ new_expr = coerce_to_domain(new_expr, InvalidOid, -1, att_tup->atttypid, COERCE_IMPLICIT_CAST, false, false); } newList = lappend(newList, new_expr); } else newList = lappend(newList, col); } newValues = lappend(newValues, newList); } rte->values_lists = newValues; } /* * matchLocks - * match the list of locks and returns the matching rules */ static List * matchLocks(CmdType event, RuleLock *rulelocks, int varno, Query *parsetree) { List *matching_locks = NIL; int nlocks; int i; if (rulelocks == NULL) return NIL; 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))) matching_locks = lappend(matching_locks, oneLock); } } return matching_locks; } /* * ApplyRetrieveRule - expand an ON SELECT rule */ static Query * ApplyRetrieveRule(Query *parsetree, RewriteRule *rule, int rt_index, bool relation_level, Relation relation, List *activeRIRs) { Query *rule_action; RangeTblEntry *rte, *subrte; RowMarkClause *rc; if (list_length(rule->actions) != 1) elog(ERROR, "expected just one rule action"); if (rule->qual != NULL) elog(ERROR, "cannot handle qualified ON SELECT rule"); if (!relation_level) elog(ERROR, "cannot handle per-attribute ON SELECT rule"); /* * Make a modifiable copy of the view query, and acquire needed locks on * the relations it mentions. */ rule_action = copyObject(linitial(rule->actions)); AcquireRewriteLocks(rule_action); /* * Recursively expand any view references inside the view. */ rule_action = fireRIRrules(rule_action, activeRIRs); /* * 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->rtekind = RTE_SUBQUERY; 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->requiredPerms = rte->requiredPerms; subrte->checkAsUser = rte->checkAsUser; rte->requiredPerms = 0; /* no permission check on subquery itself */ rte->checkAsUser = InvalidOid; /* * FOR UPDATE/SHARE of view? */ if ((rc = get_rowmark(parsetree, rt_index)) != NULL) { /* * Remove the view from the list of rels that will actually be marked * FOR UPDATE/SHARE by the executor. It will still be access-checked * for write access, though. */ parsetree->rowMarks = list_delete_ptr(parsetree->rowMarks, rc); /* * Set up the view's referenced tables as if FOR UPDATE/SHARE. */ markQueryForLocking(rule_action, rc->forUpdate, rc->noWait, true); } return parsetree; } /* * Recursively mark all relations used by a view as FOR UPDATE/SHARE. * * This may generate an invalid query, eg if some sub-query uses an * aggregate. We leave it to the planner to detect that. * * NB: this must agree with the parser's transformLocking() routine. */ static void markQueryForLocking(Query *qry, bool forUpdate, bool noWait, bool skipOldNew) { Index rti = 0; ListCell *l; foreach(l, qry->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(l); rti++; /* Ignore OLD and NEW entries if we are at top level of view */ if (skipOldNew && (rti == PRS2_OLD_VARNO || rti == PRS2_NEW_VARNO)) continue; if (rte->rtekind == RTE_RELATION) { applyLockingClause(qry, rti, forUpdate, noWait); rte->requiredPerms |= ACL_SELECT_FOR_UPDATE; } else if (rte->rtekind == RTE_SUBQUERY) { /* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */ markQueryForLocking(rte->subquery, forUpdate, noWait, false); } } } /* * 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, List *activeRIRs) { 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, activeRIRs); /* 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 *) activeRIRs); } /* * fireRIRrules - * Apply all RIR rules on each rangetable entry in a query */ static Query * fireRIRrules(Query *parsetree, List *activeRIRs) { int rt_index; /* * 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 < list_length(parsetree->rtable)) { RangeTblEntry *rte; Relation rel; List *locks; RuleLock *rules; RewriteRule *rule; int i; ++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->rtekind == RTE_SUBQUERY) { rte->subquery = fireRIRrules(rte->subquery, activeRIRs); continue; } /* * Joins and other non-relation RTEs can be ignored completely. */ if (rte->rtekind != RTE_RELATION) 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. */ if (rt_index != parsetree->resultRelation && !rangeTableEntry_used((Node *) parsetree, rt_index, 0)) continue; /* * We can use NoLock here since either the parser or * AcquireRewriteLocks should have locked the rel already. */ rel = heap_open(rte->relid, NoLock); /* * Collect the RIR rules that we must apply */ rules = rel->rd_rules; if (rules == NULL) { heap_close(rel, NoLock); continue; } 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); } /* * If we found any, apply them --- but first check for recursion! */ if (locks != NIL) { ListCell *l; if (list_member_oid(activeRIRs, RelationGetRelid(rel))) ereport(ERROR, (errcode(ERRCODE_INVALID_OBJECT_DEFINITION), errmsg("infinite recursion detected in rules for relation \"%s\"", RelationGetRelationName(rel)))); activeRIRs = lcons_oid(RelationGetRelid(rel), activeRIRs); foreach(l, locks) { rule = lfirst(l); parsetree = ApplyRetrieveRule(parsetree, rule, rt_index, rule->attrno == -1, rel, activeRIRs); } activeRIRs = list_delete_first(activeRIRs); } heap_close(rel, NoLock); } /* * Recurse into sublink subqueries, too. But we already did the ones in * the rtable. */ if (parsetree->hasSubLinks) query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs, QTW_IGNORE_RT_SUBQUERIES); return parsetree; } /* * Modify the given query by adding 'AND rule_qual IS NOT TRUE' to its * qualification. This is used to generate suitable "else clauses" for * conditional INSTEAD rules. (Unfortunately we must use "x IS NOT TRUE", * not just "NOT x" which the planner is much smarter about, else we will * do the wrong thing when the qual evaluates to NULL.) * * The rule_qual may contain references to OLD or NEW. OLD references are * replaced by references to the specified rt_index (the relation that the * rule applies to). NEW references are only possible for INSERT and UPDATE * queries on the relation itself, and so they should be replaced by copies * of the related entries in the query's own targetlist. */ static Query * CopyAndAddInvertedQual(Query *parsetree, Node *rule_qual, int rt_index, CmdType event) { /* Don't scribble on the passed qual (it's in the relcache!) */ Node *new_qual = (Node *) copyObject(rule_qual); /* * In case there are subqueries in the qual, acquire necessary locks and * fix any deleted JOIN RTE entries. (This is somewhat redundant with * rewriteRuleAction, but not entirely ... consider restructuring so that * we only need to process the qual this way once.) */ (void) acquireLocksOnSubLinks(new_qual, NULL); /* Fix references to OLD */ ChangeVarNodes(new_qual, PRS2_OLD_VARNO, rt_index, 0); /* Fix references to NEW */ if (event == CMD_INSERT || event == CMD_UPDATE) new_qual = ResolveNew(new_qual, PRS2_NEW_VARNO, 0, rt_fetch(rt_index, parsetree->rtable), parsetree->targetList, event, rt_index); /* And attach the fixed qual */ AddInvertedQual(parsetree, new_qual); return parsetree; } /* * fireRules - * Iterate through rule locks applying rules. * * Input arguments: * parsetree - original query * rt_index - RT index of result relation in original query * event - type of rule event * locks - list of rules to fire * Output arguments: * *instead_flag - set TRUE if any unqualified INSTEAD rule is found * (must be initialized to FALSE) * *qual_product - filled with modified original query if any qualified * INSTEAD rule is found (must be initialized to NULL) * Return value: * list of rule actions adjusted for use with this query * * Qualified INSTEAD rules generate their action with the qualification * condition added. They also generate a modified version of the original * query with the negated qualification added, so that it will run only for * rows that the qualified action doesn't act on. (If there are multiple * qualified INSTEAD rules, we AND all the negated quals onto a single * modified original query.) We won't execute the original, unmodified * query if we find either qualified or unqualified INSTEAD rules. If * we find both, the modified original query is discarded too. */ static List * fireRules(Query *parsetree, int rt_index, CmdType event, List *locks, bool *instead_flag, Query **qual_product) { List *results = NIL; ListCell *l; foreach(l, locks) { RewriteRule *rule_lock = (RewriteRule *) lfirst(l); Node *event_qual = rule_lock->qual; List *actions = rule_lock->actions; QuerySource qsrc; ListCell *r; /* Determine correct QuerySource value for actions */ if (rule_lock->isInstead) { if (event_qual != NULL) qsrc = QSRC_QUAL_INSTEAD_RULE; else { qsrc = QSRC_INSTEAD_RULE; *instead_flag = true; /* report unqualified INSTEAD */ } } else qsrc = QSRC_NON_INSTEAD_RULE; if (qsrc == QSRC_QUAL_INSTEAD_RULE) { /* * 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_product so RewriteQuery() can add it to the query * list after we mangled it up enough. * * If we have already found an unqualified INSTEAD rule, then * *qual_product won't be used, so don't bother building it. */ if (!*instead_flag) { if (*qual_product == NULL) *qual_product = copyObject(parsetree); *qual_product = CopyAndAddInvertedQual(*qual_product, event_qual, rt_index, event); } } /* Now process the rule's actions and add them to the result list */ foreach(r, actions) { Query *rule_action = lfirst(r); if (rule_action->commandType == CMD_NOTHING) continue; rule_action = rewriteRuleAction(parsetree, rule_action, event_qual, rt_index, event); rule_action->querySource = qsrc; rule_action->canSetTag = false; /* might change later */ results = lappend(results, rule_action); } } return results; } /* * RewriteQuery - * rewrites the query and apply the rules again on the queries rewritten * * rewrite_events is a list of open query-rewrite actions, so we can detect * infinite recursion. */ static List * RewriteQuery(Query *parsetree, List *rewrite_events) { CmdType event = parsetree->commandType; bool instead = false; Query *qual_product = NULL; List *rewritten = NIL; /* * If the statement is an update, insert or delete - fire rules on it. * * SELECT rules are handled later when we have all the queries that should * get executed. Also, utilities aren't rewritten at all (do we still * need that check?) */ if (event != CMD_SELECT && event != CMD_UTILITY) { int result_relation; RangeTblEntry *rt_entry; Relation rt_entry_relation; List *locks; result_relation = parsetree->resultRelation; Assert(result_relation != 0); rt_entry = rt_fetch(result_relation, parsetree->rtable); Assert(rt_entry->rtekind == RTE_RELATION); /* * We can use NoLock here since either the parser or * AcquireRewriteLocks should have locked the rel already. */ rt_entry_relation = heap_open(rt_entry->relid, NoLock); /* * If it's an INSERT or UPDATE, rewrite the targetlist into standard * form. This will be needed by the planner anyway, and doing it now * ensures that any references to NEW.field will behave sanely. */ if (event == CMD_UPDATE) rewriteTargetList(parsetree, rt_entry_relation, NULL); else if (event == CMD_INSERT) { RangeTblEntry *values_rte = NULL; /* * If it's an INSERT ... VALUES (...), (...), ... * there will be a single RTE for the VALUES targetlists. */ if (list_length(parsetree->jointree->fromlist) == 1) { RangeTblRef *rtr = (RangeTblRef *) linitial(parsetree->jointree->fromlist); if (IsA(rtr, RangeTblRef)) { RangeTblEntry *rte = rt_fetch(rtr->rtindex, parsetree->rtable); if (rte->rtekind == RTE_VALUES) values_rte = rte; } } if (values_rte) { List *attrnos; /* Process the main targetlist ... */ rewriteTargetList(parsetree, rt_entry_relation, &attrnos); /* ... and the VALUES expression lists */ rewriteValuesRTE(values_rte, rt_entry_relation, attrnos); } else { /* Process just the main targetlist */ rewriteTargetList(parsetree, rt_entry_relation, NULL); } } /* * Collect and apply the appropriate rules. */ locks = matchLocks(event, rt_entry_relation->rd_rules, result_relation, parsetree); if (locks != NIL) { List *product_queries; product_queries = fireRules(parsetree, result_relation, event, locks, &instead, &qual_product); /* * If we got any product queries, recursively rewrite them --- but * first check for recursion! */ if (product_queries != NIL) { ListCell *n; rewrite_event *rev; foreach(n, rewrite_events) { rev = (rewrite_event *) lfirst(n); if (rev->relation == RelationGetRelid(rt_entry_relation) && rev->event == event) ereport(ERROR, (errcode(ERRCODE_INVALID_OBJECT_DEFINITION), errmsg("infinite recursion detected in rules for relation \"%s\"", RelationGetRelationName(rt_entry_relation)))); } rev = (rewrite_event *) palloc(sizeof(rewrite_event)); rev->relation = RelationGetRelid(rt_entry_relation); rev->event = event; rewrite_events = lcons(rev, rewrite_events); foreach(n, product_queries) { Query *pt = (Query *) lfirst(n); List *newstuff; newstuff = RewriteQuery(pt, rewrite_events); rewritten = list_concat(rewritten, newstuff); } rewrite_events = list_delete_first(rewrite_events); } } heap_close(rt_entry_relation, NoLock); } /* * For INSERTs, the original query is done first; for UPDATE/DELETE, it is * done last. This is needed 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 executions * makes the deleted (and maybe the updated) tuples disappear so the scans * for them in the rule actions cannot find them. * * If we found any unqualified INSTEAD, the original query is not done at * all, in any form. Otherwise, we add the modified form if qualified * INSTEADs were found, else the unmodified form. */ if (!instead) { if (parsetree->commandType == CMD_INSERT) { if (qual_product != NULL) rewritten = lcons(qual_product, rewritten); else rewritten = lcons(parsetree, rewritten); } else { if (qual_product != NULL) rewritten = lappend(rewritten, qual_product); else rewritten = lappend(rewritten, parsetree); } } return rewritten; } /* * QueryRewrite - * Primary entry point to the query rewriter. * Rewrite one query via query rewrite system, possibly returning 0 * or many queries. * * NOTE: the parsetree must either have come straight from the parser, * or have been scanned by AcquireRewriteLocks to acquire suitable locks. */ List * QueryRewrite(Query *parsetree) { List *querylist; List *results = NIL; ListCell *l; CmdType origCmdType; bool foundOriginalQuery; Query *lastInstead; /* * Step 1 * * Apply all non-SELECT rules possibly getting 0 or many queries */ querylist = RewriteQuery(parsetree, NIL); /* * Step 2 * * Apply all the RIR rules on each query */ foreach(l, querylist) { Query *query = (Query *) lfirst(l); query = fireRIRrules(query, NIL); /* * If the query target was rewritten as a view, complain. */ if (query->resultRelation) { RangeTblEntry *rte = rt_fetch(query->resultRelation, query->rtable); if (rte->rtekind == RTE_SUBQUERY) { switch (query->commandType) { case CMD_INSERT: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot insert into a view"), errhint("You need an unconditional ON INSERT DO INSTEAD rule."))); break; case CMD_UPDATE: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot update a view"), errhint("You need an unconditional ON UPDATE DO INSTEAD rule."))); break; case CMD_DELETE: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot delete from a view"), errhint("You need an unconditional ON DELETE DO INSTEAD rule."))); break; default: elog(ERROR, "unrecognized commandType: %d", (int) query->commandType); break; } } } results = lappend(results, query); } /* * Step 3 * * Determine which, if any, of the resulting queries is supposed to set * the command-result tag; and update the canSetTag fields accordingly. * * If the original query is still in the list, it sets the command tag. * Otherwise, the last INSTEAD query of the same kind as the original is * allowed to set the tag. (Note these rules can leave us with no query * setting the tag. The tcop code has to cope with this by setting up a * default tag based on the original un-rewritten query.) * * The Asserts verify that at most one query in the result list is marked * canSetTag. If we aren't checking asserts, we can fall out of the loop * as soon as we find the original query. */ origCmdType = parsetree->commandType; foundOriginalQuery = false; lastInstead = NULL; foreach(l, results) { Query *query = (Query *) lfirst(l); if (query->querySource == QSRC_ORIGINAL) { Assert(query->canSetTag); Assert(!foundOriginalQuery); foundOriginalQuery = true; #ifndef USE_ASSERT_CHECKING break; #endif } else { Assert(!query->canSetTag); if (query->commandType == origCmdType && (query->querySource == QSRC_INSTEAD_RULE || query->querySource == QSRC_QUAL_INSTEAD_RULE)) lastInstead = query; } } if (!foundOriginalQuery && lastInstead != NULL) lastInstead->canSetTag = true; return results; }