/*------------------------------------------------------------------------- * * rewriteHandler.c * Primary module of query rewriter. * * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * src/backend/rewrite/rewriteHandler.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/sysattr.h" #include "catalog/pg_type.h" #include "commands/trigger.h" #include "foreign/fdwapi.h" #include "nodes/makefuncs.h" #include "nodes/nodeFuncs.h" #include "parser/analyze.h" #include "parser/parse_coerce.h" #include "parser/parsetree.h" #include "rewrite/rewriteDefine.h" #include "rewrite/rewriteHandler.h" #include "rewrite/rewriteManip.h" #include "utils/builtins.h" #include "utils/lsyscache.h" #include "utils/rel.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, bool *returning_flag); static List *adjustJoinTreeList(Query *parsetree, bool removert, int rt_index); static void rewriteTargetListIU(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 rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte, Relation target_relation); static void markQueryForLocking(Query *qry, Node *jtnode, LockClauseStrength strength, bool noWait, bool pushedDown); static List *matchLocks(CmdType event, RuleLock *rulelocks, int varno, Query *parsetree); static Query *fireRIRrules(Query *parsetree, List *activeRIRs, bool forUpdatePushedDown); static bool view_has_instead_trigger(Relation view, CmdType event); static Bitmapset *adjust_view_column_set(Bitmapset *cols, List *targetlist); /* * 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. * * forUpdatePushedDown indicates that a pushed-down FOR [KEY] UPDATE/SHARE applies * to the current subquery, requiring all rels to be opened with RowShareLock. * This should always be false at the start of the recursion. * * 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 pointers. * * (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, bool forUpdatePushedDown) { 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 [KEY] 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 (forUpdatePushedDown || get_parse_rowmark(parsetree, rt_index) != NULL) lockmode = RowShareLock; else lockmode = AccessShareLock; rel = heap_open(rte->relid, lockmode); /* * While we have the relation open, update the RTE's relkind, * just in case it changed since this rule was made. */ rte->relkind = rel->rd_rel->relkind; 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 * pointers. * * 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 *aliasitem = (Var *) lfirst(ll); Var *aliasvar = aliasitem; /* Look through any implicit coercion */ aliasvar = (Var *) strip_implicit_coercions((Node *) aliasvar); /* * 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 * pointer already? But that's OK too.) */ if (aliasvar && 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)) { /* Replace the join alias item with a NULL */ aliasitem = NULL; } } newaliasvars = lappend(newaliasvars, aliasitem); } 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, (forUpdatePushedDown || get_parse_rowmark(parsetree, rt_index) != NULL)); break; default: /* ignore other types of RTEs */ break; } } /* Recurse into subqueries in WITH */ foreach(l, parsetree->cteList) { CommonTableExpr *cte = (CommonTableExpr *) lfirst(l); AcquireRewriteLocks((Query *) cte->ctequery, false); } /* * Recurse into sublink subqueries, too. But we already did the ones in * the rtable and cteList. */ if (parsetree->hasSubLinks) query_tree_walker(parsetree, acquireLocksOnSubLinks, NULL, QTW_IGNORE_RC_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, false); /* 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). * * Input arguments: * parsetree - original query * rule_action - one action (query) of a rule * rule_qual - WHERE condition of rule, or NULL if unconditional * rt_index - RT index of result relation in original query * event - type of rule event * Output arguments: * *returning_flag - set TRUE if we rewrite RETURNING clause in rule_action * (must be initialized to FALSE) * Return value: * rewritten form of rule_action */ static Query * rewriteRuleAction(Query *parsetree, Query *rule_action, Node *rule_qual, int rt_index, CmdType event, bool *returning_flag) { 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, false); (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); /* * There could have been some SubLinks in parsetree's rtable, in which * case we'd better mark the sub_action correctly. */ if (parsetree->hasSubLinks && !sub_action->hasSubLinks) { ListCell *lc; foreach(lc, parsetree->rtable) { RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc); switch (rte->rtekind) { case RTE_FUNCTION: sub_action->hasSubLinks = checkExprHasSubLink(rte->funcexpr); break; case RTE_VALUES: sub_action->hasSubLinks = checkExprHasSubLink((Node *) rte->values_lists); break; default: /* other RTE types don't contain bare expressions */ break; } if (sub_action->hasSubLinks) break; /* no need to keep scanning 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); } } /* * If the original query has any CTEs, copy them into the rule action. But * we don't need them for a utility action. */ if (parsetree->cteList != NIL && sub_action->commandType != CMD_UTILITY) { ListCell *lc; /* * Annoying implementation restriction: because CTEs are identified by * name within a cteList, we can't merge a CTE from the original query * if it has the same name as any CTE in the rule action. * * This could possibly be fixed by using some sort of internally * generated ID, instead of names, to link CTE RTEs to their CTEs. */ foreach(lc, parsetree->cteList) { CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc); ListCell *lc2; foreach(lc2, sub_action->cteList) { CommonTableExpr *cte2 = (CommonTableExpr *) lfirst(lc2); if (strcmp(cte->ctename, cte2->ctename) == 0) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("WITH query name \"%s\" appears in both a rule action and the query being rewritten", cte->ctename))); } } /* OK, it's safe to combine the CTE lists */ sub_action->cteList = list_concat(sub_action->cteList, copyObject(parsetree->cteList)); } /* * 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 with right hand side of target-list entry for * appropriate field name in insert/update. * * KLUGE ALERT: since ReplaceVarsFromTargetList 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 *) ReplaceVarsFromTargetList((Node *) sub_action, new_varno, 0, rt_fetch(new_varno, sub_action->rtable), parsetree->targetList, (event == CMD_UPDATE) ? REPLACEVARS_CHANGE_VARNO : REPLACEVARS_SUBSTITUTE_NULL, current_varno, NULL); if (sub_action_ptr) *sub_action_ptr = sub_action; else rule_action = sub_action; } /* * If rule_action has a RETURNING clause, then either throw it away if the * triggering query has no RETURNING clause, or rewrite it to emit what * the triggering query's RETURNING clause asks for. Throw an error if * more than one rule has a RETURNING clause. */ if (!parsetree->returningList) rule_action->returningList = NIL; else if (rule_action->returningList) { if (*returning_flag) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot have RETURNING lists in multiple rules"))); *returning_flag = true; rule_action->returningList = (List *) ReplaceVarsFromTargetList((Node *) parsetree->returningList, parsetree->resultRelation, 0, rt_fetch(parsetree->resultRelation, parsetree->rtable), rule_action->returningList, REPLACEVARS_REPORT_ERROR, 0, &rule_action->hasSubLinks); /* * There could have been some SubLinks in parsetree's returningList, * in which case we'd better mark the rule_action correctly. */ if (parsetree->hasSubLinks && !rule_action->hasSubLinks) rule_action->hasSubLinks = checkExprHasSubLink((Node *) rule_action->returningList); } 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; } /* * rewriteTargetListIU - 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. For an UPDATE on a trigger-updatable view, add tlist entries for any * unassigned-to attributes, assigning them their old values. These will * later get expanded to the output values of the view. (This is equivalent * to what the planner's expand_targetlist() will do for UPDATE on a regular * table, but it's more convenient to do it here while we still have easy * access to the view's original RT index.) This is only necessary for * trigger-updatable views, for which the view remains the result relation of * the query. For auto-updatable views we must not do this, since it might * add assignments to non-updatable view columns. For rule-updatable views it * is unnecessary extra work, since the query will be rewritten with a * different result relation which will be processed when we recurse via * RewriteQuery. * * 3. 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) * * 4. 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 1,2,3 before firing rewrite rules, else rewritten * references to NEW.foo will produce wrong or incomplete results. Item 4 * is not needed for rewriting, but will be needed by the planner, and we * can do it essentially for free while handling the other items. * * 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 rewriteTargetListIU(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, -1, att_tup->attcollation, 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, -1, false, false); } } if (new_expr) new_tle = makeTargetEntry((Expr *) new_expr, attrno, pstrdup(NameStr(att_tup->attname)), false); } /* * For an UPDATE on a trigger-updatable view, provide a dummy entry * whenever there is no explicit assignment. */ if (new_tle == NULL && commandType == CMD_UPDATE && target_relation->rd_rel->relkind == RELKIND_VIEW && view_has_instead_trigger(target_relation, CMD_UPDATE)) { Node *new_expr; new_expr = (Node *) makeVar(parsetree->resultRelation, attrno, att_tup->atttypid, att_tup->atttypmod, att_tup->attcollation, 0); 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, "cannot 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, -1); 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 targetlist * rewriting 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, -1, att_tup->attcollation, 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, -1, false, false); } newList = lappend(newList, new_expr); } else newList = lappend(newList, col); } newValues = lappend(newValues, newList); } rte->values_lists = newValues; } /* * rewriteTargetListUD - rewrite UPDATE/DELETE targetlist as needed * * This function adds a "junk" TLE that is needed to allow the executor to * find the original row for the update or delete. When the target relation * is a regular table, the junk TLE emits the ctid attribute of the original * row. When the target relation is a view, there is no ctid, so we instead * emit a whole-row Var that will contain the "old" values of the view row. * If it's a foreign table, we let the FDW decide what to add. * * For UPDATE queries, this is applied after rewriteTargetListIU. The * ordering isn't actually critical at the moment. */ static void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte, Relation target_relation) { Var *var; const char *attrname; TargetEntry *tle; if (target_relation->rd_rel->relkind == RELKIND_RELATION || target_relation->rd_rel->relkind == RELKIND_MATVIEW) { /* * Emit CTID so that executor can find the row to update or delete. */ var = makeVar(parsetree->resultRelation, SelfItemPointerAttributeNumber, TIDOID, -1, InvalidOid, 0); attrname = "ctid"; } else if (target_relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE) { /* * Let the foreign table's FDW add whatever junk TLEs it wants. */ FdwRoutine *fdwroutine; fdwroutine = GetFdwRoutineForRelation(target_relation, false); if (fdwroutine->AddForeignUpdateTargets != NULL) fdwroutine->AddForeignUpdateTargets(parsetree, target_rte, target_relation); return; } else { /* * Emit whole-row Var so that executor will have the "old" view row to * pass to the INSTEAD OF trigger. */ var = makeWholeRowVar(target_rte, parsetree->resultRelation, 0, false); attrname = "wholerow"; } tle = makeTargetEntry((Expr *) var, list_length(parsetree->targetList) + 1, pstrdup(attrname), true); parsetree->targetList = lappend(parsetree->targetList, tle); } /* * 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]; /* * Suppress ON INSERT/UPDATE/DELETE rules that are disabled or * configured to not fire during the current sessions replication * role. ON SELECT rules will always be applied in order to keep views * working even in LOCAL or REPLICA role. */ if (oneLock->event != CMD_SELECT) { if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA) { if (oneLock->enabled == RULE_FIRES_ON_ORIGIN || oneLock->enabled == RULE_DISABLED) continue; } else /* ORIGIN or LOCAL ROLE */ { if (oneLock->enabled == RULE_FIRES_ON_REPLICA || oneLock->enabled == RULE_DISABLED) continue; } } if (oneLock->event == event) { if (parsetree->commandType != CMD_SELECT || rangeTableEntry_used((Node *) parsetree, varno, 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, Relation relation, List *activeRIRs, bool forUpdatePushedDown) { 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 (rt_index == parsetree->resultRelation) { /* * We have a view as the result relation of the query, and it wasn't * rewritten by any rule. This case is supported if there is an * INSTEAD OF trigger that will trap attempts to insert/update/delete * view rows. The executor will check that; for the moment just plow * ahead. We have two cases: * * For INSERT, we needn't do anything. The unmodified RTE will serve * fine as the result relation. * * For UPDATE/DELETE, we need to expand the view so as to have source * data for the operation. But we also need an unmodified RTE to * serve as the target. So, copy the RTE and add the copy to the * rangetable. Note that the copy does not get added to the jointree. * Also note that there's a hack in fireRIRrules to avoid calling this * function again when it arrives at the copied RTE. */ if (parsetree->commandType == CMD_INSERT) return parsetree; else if (parsetree->commandType == CMD_UPDATE || parsetree->commandType == CMD_DELETE) { RangeTblEntry *newrte; rte = rt_fetch(rt_index, parsetree->rtable); newrte = copyObject(rte); parsetree->rtable = lappend(parsetree->rtable, newrte); parsetree->resultRelation = list_length(parsetree->rtable); /* * There's no need to do permissions checks twice, so wipe out the * permissions info for the original RTE (we prefer to keep the * bits set on the result RTE). */ rte->requiredPerms = 0; rte->checkAsUser = InvalidOid; rte->selectedCols = NULL; rte->modifiedCols = NULL; /* * For the most part, Vars referencing the view should remain as * they are, meaning that they implicitly represent OLD values. * But in the RETURNING list if any, we want such Vars to * represent NEW values, so change them to reference the new RTE. * * Since ChangeVarNodes scribbles on the tree in-place, copy the * RETURNING list first for safety. */ parsetree->returningList = copyObject(parsetree->returningList); ChangeVarNodes((Node *) parsetree->returningList, rt_index, parsetree->resultRelation, 0); /* Now, continue with expanding the original view RTE */ } else elog(ERROR, "unrecognized commandType: %d", (int) parsetree->commandType); } /* * If FOR [KEY] UPDATE/SHARE of view, be sure we get right initial lock on * the relations it references. */ rc = get_parse_rowmark(parsetree, rt_index); forUpdatePushedDown |= (rc != NULL); /* * 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, forUpdatePushedDown); /* * Recursively expand any view references inside the view. */ rule_action = fireRIRrules(rule_action, activeRIRs, forUpdatePushedDown); /* * Now, 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->security_barrier = RelationIsSecurityView(relation); 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; subrte->selectedCols = rte->selectedCols; subrte->modifiedCols = rte->modifiedCols; rte->requiredPerms = 0; /* no permission check on subquery itself */ rte->checkAsUser = InvalidOid; rte->selectedCols = NULL; rte->modifiedCols = NULL; /* * If FOR [KEY] UPDATE/SHARE of view, mark all the contained tables as * implicit FOR [KEY] UPDATE/SHARE, the same as the parser would have done * if the view's subquery had been written out explicitly. * * Note: we don't consider forUpdatePushedDown here; such marks will be * made by recursing from the upper level in markQueryForLocking. */ if (rc != NULL) markQueryForLocking(rule_action, (Node *) rule_action->jointree, rc->strength, rc->noWait, true); return parsetree; } /* * Recursively mark all relations used by a view as FOR [KEY] 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 transformLockingClause() routine. * However, unlike the parser we have to be careful not to mark a view's * OLD and NEW rels for updating. The best way to handle that seems to be * to scan the jointree to determine which rels are used. */ static void markQueryForLocking(Query *qry, Node *jtnode, LockClauseStrength strength, bool noWait, bool pushedDown) { if (jtnode == NULL) return; if (IsA(jtnode, RangeTblRef)) { int rti = ((RangeTblRef *) jtnode)->rtindex; RangeTblEntry *rte = rt_fetch(rti, qry->rtable); if (rte->rtekind == RTE_RELATION) { applyLockingClause(qry, rti, strength, noWait, pushedDown); rte->requiredPerms |= ACL_SELECT_FOR_UPDATE; } else if (rte->rtekind == RTE_SUBQUERY) { applyLockingClause(qry, rti, strength, noWait, pushedDown); /* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */ markQueryForLocking(rte->subquery, (Node *) rte->subquery->jointree, strength, noWait, true); } /* other RTE types are unaffected by FOR UPDATE */ } else if (IsA(jtnode, FromExpr)) { FromExpr *f = (FromExpr *) jtnode; ListCell *l; foreach(l, f->fromlist) markQueryForLocking(qry, lfirst(l), strength, noWait, pushedDown); } else if (IsA(jtnode, JoinExpr)) { JoinExpr *j = (JoinExpr *) jtnode; markQueryForLocking(qry, j->larg, strength, noWait, pushedDown); markQueryForLocking(qry, j->rarg, strength, noWait, pushedDown); } else elog(ERROR, "unrecognized node type: %d", (int) nodeTag(jtnode)); } /* * 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, false); /* 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, bool forUpdatePushedDown) { int origResultRelation = parsetree->resultRelation; int rt_index; ListCell *lc; /* * 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, (forUpdatePushedDown || get_parse_rowmark(parsetree, rt_index) != NULL)); continue; } /* * Joins and other non-relation RTEs can be ignored completely. */ if (rte->rtekind != RTE_RELATION) continue; /* * Always ignore RIR rules for materialized views referenced in * queries. (This does not prevent refreshing MVs, since they aren't * referenced in their own query definitions.) * * Note: in the future we might want to allow MVs to be conditionally * expanded as if they were regular views, if they are not scannable. * In that case this test would need to be postponed till after we've * opened the rel, so that we could check its state. */ if (rte->relkind == RELKIND_MATVIEW) 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; /* * Also, if this is a new result relation introduced by * ApplyRetrieveRule, we don't want to do anything more with it. */ if (rt_index == parsetree->resultRelation && rt_index != origResultRelation) 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; 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, rel, activeRIRs, forUpdatePushedDown); } activeRIRs = list_delete_first(activeRIRs); } heap_close(rel, NoLock); } /* Recurse into subqueries in WITH */ foreach(lc, parsetree->cteList) { CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc); cte->ctequery = (Node *) fireRIRrules((Query *) cte->ctequery, activeRIRs, false); } /* * Recurse into sublink subqueries, too. But we already did the ones in * the rtable and cteList. */ if (parsetree->hasSubLinks) query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs, QTW_IGNORE_RC_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 = ReplaceVarsFromTargetList(new_qual, PRS2_NEW_VARNO, 0, rt_fetch(rt_index, parsetree->rtable), parsetree->targetList, (event == CMD_UPDATE) ? REPLACEVARS_CHANGE_VARNO : REPLACEVARS_SUBSTITUTE_NULL, rt_index, &parsetree->hasSubLinks); /* 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) * *returning_flag - set TRUE if we rewrite RETURNING clause in any rule * (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, bool *returning_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, returning_flag); rule_action->querySource = qsrc; rule_action->canSetTag = false; /* might change later */ results = lappend(results, rule_action); } } return results; } /* * get_view_query - get the Query from a view's _RETURN rule. * * Caller should have verified that the relation is a view, and therefore * we should find an ON SELECT action. */ Query * get_view_query(Relation view) { int i; Assert(view->rd_rel->relkind == RELKIND_VIEW); for (i = 0; i < view->rd_rules->numLocks; i++) { RewriteRule *rule = view->rd_rules->rules[i]; if (rule->event == CMD_SELECT) { /* A _RETURN rule should have only one action */ if (list_length(rule->actions) != 1) elog(ERROR, "invalid _RETURN rule action specification"); return (Query *) linitial(rule->actions); } } elog(ERROR, "failed to find _RETURN rule for view"); return NULL; /* keep compiler quiet */ } /* * view_has_instead_trigger - does view have an INSTEAD OF trigger for event? * * If it does, we don't want to treat it as auto-updatable. This test can't * be folded into view_query_is_auto_updatable because it's not an error * condition. */ static bool view_has_instead_trigger(Relation view, CmdType event) { TriggerDesc *trigDesc = view->trigdesc; switch (event) { case CMD_INSERT: if (trigDesc && trigDesc->trig_insert_instead_row) return true; break; case CMD_UPDATE: if (trigDesc && trigDesc->trig_update_instead_row) return true; break; case CMD_DELETE: if (trigDesc && trigDesc->trig_delete_instead_row) return true; break; default: elog(ERROR, "unrecognized CmdType: %d", (int) event); break; } return false; } /* * view_col_is_auto_updatable - test whether the specified column of a view * is auto-updatable. Returns NULL (if the column can be updated) or a message * string giving the reason that it cannot be. * * Note that the checks performed here are local to this view. We do not check * whether the referenced column of the underlying base relation is updatable. */ static const char * view_col_is_auto_updatable(RangeTblRef *rtr, TargetEntry *tle) { Var *var = (Var *) tle->expr; /* * For now, the only updatable columns we support are those that are Vars * referring to user columns of the underlying base relation. * * The view targetlist may contain resjunk columns (e.g., a view defined * like "SELECT * FROM t ORDER BY a+b" is auto-updatable) but such columns * are not auto-updatable, and in fact should never appear in the outer * query's targetlist. */ if (tle->resjunk) return gettext_noop("Junk view columns are not updatable."); if (!IsA(var, Var) || var->varno != rtr->rtindex || var->varlevelsup != 0) return gettext_noop("View columns that are not columns of their base relation are not updatable."); if (var->varattno < 0) return gettext_noop("View columns that refer to system columns are not updatable."); if (var->varattno == 0) return gettext_noop("View columns that return whole-row references are not updatable."); return NULL; /* the view column is updatable */ } /* * view_query_is_auto_updatable - test whether the specified view definition * represents an auto-updatable view. Returns NULL (if the view can be updated) * or a message string giving the reason that it cannot be. * * If check_cols is true, the view is required to have at least one updatable * column (necessary for INSERT/UPDATE). Otherwise the view's columns are not * checked for updatability. See also view_cols_are_auto_updatable. * * Note that the checks performed here are only based on the view definition. * We do not check whether any base relations referred to by the view are * updatable. */ const char * view_query_is_auto_updatable(Query *viewquery, bool security_barrier, bool check_cols) { RangeTblRef *rtr; RangeTblEntry *base_rte; /*---------- * Check if the view is simply updatable. According to SQL-92 this means: * - No DISTINCT clause. * - Each TLE is a column reference, and each column appears at most once. * - FROM contains exactly one base relation. * - No GROUP BY or HAVING clauses. * - No set operations (UNION, INTERSECT or EXCEPT). * - No sub-queries in the WHERE clause that reference the target table. * * We ignore that last restriction since it would be complex to enforce * and there isn't any actual benefit to disallowing sub-queries. (The * semantic issues that the standard is presumably concerned about don't * arise in Postgres, since any such sub-query will not see any updates * executed by the outer query anyway, thanks to MVCC snapshotting.) * * We also relax the second restriction by supporting part of SQL:1999 * feature T111, which allows for a mix of updatable and non-updatable * columns, provided that an INSERT or UPDATE doesn't attempt to assign to * a non-updatable column. * * In addition we impose these constraints, involving features that are * not part of SQL-92: * - No CTEs (WITH clauses). * - No OFFSET or LIMIT clauses (this matches a SQL:2008 restriction). * - No system columns (including whole-row references) in the tlist. * - No window functions in the tlist. * - No set-returning functions in the tlist. * * Note that we do these checks without recursively expanding the view. * If the base relation is a view, we'll recursively deal with it later. *---------- */ if (viewquery->distinctClause != NIL) return gettext_noop("Views containing DISTINCT are not automatically updatable."); if (viewquery->groupClause != NIL) return gettext_noop("Views containing GROUP BY are not automatically updatable."); if (viewquery->havingQual != NULL) return gettext_noop("Views containing HAVING are not automatically updatable."); if (viewquery->setOperations != NULL) return gettext_noop("Views containing UNION, INTERSECT, or EXCEPT are not automatically updatable."); if (viewquery->cteList != NIL) return gettext_noop("Views containing WITH are not automatically updatable."); if (viewquery->limitOffset != NULL || viewquery->limitCount != NULL) return gettext_noop("Views containing LIMIT or OFFSET are not automatically updatable."); /* * We must not allow window functions or set returning functions in the * targetlist. Otherwise we might end up inserting them into the quals of * the main query. We must also check for aggregates in the targetlist in * case they appear without a GROUP BY. * * These restrictions ensure that each row of the view corresponds to a * unique row in the underlying base relation. */ if (viewquery->hasAggs) return gettext_noop("Views that return aggregate functions are not automatically updatable"); if (viewquery->hasWindowFuncs) return gettext_noop("Views that return window functions are not automatically updatable"); if (expression_returns_set((Node *) viewquery->targetList)) return gettext_noop("Views that return set-returning functions are not automatically updatable."); /* * For now, we also don't support security-barrier views, because of the * difficulty of keeping upper-level qual expressions away from * lower-level data. This might get relaxed in the future. */ if (security_barrier) return gettext_noop("Security-barrier views are not automatically updatable."); /* * The view query should select from a single base relation, which must be * a table or another view. */ if (list_length(viewquery->jointree->fromlist) != 1) return gettext_noop("Views that do not select from a single table or view are not automatically updatable."); rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist); if (!IsA(rtr, RangeTblRef)) return gettext_noop("Views that do not select from a single table or view are not automatically updatable."); base_rte = rt_fetch(rtr->rtindex, viewquery->rtable); if (base_rte->rtekind != RTE_RELATION || (base_rte->relkind != RELKIND_RELATION && base_rte->relkind != RELKIND_FOREIGN_TABLE && base_rte->relkind != RELKIND_VIEW)) return gettext_noop("Views that do not select from a single table or view are not automatically updatable."); /* * Check that the view has at least one updatable column. This is required * for INSERT/UPDATE but not for DELETE. */ if (check_cols) { ListCell *cell; bool found; found = false; foreach(cell, viewquery->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(cell); if (view_col_is_auto_updatable(rtr, tle) == NULL) { found = true; break; } } if (!found) return gettext_noop("Views that have no updatable columns are not automatically updatable."); } return NULL; /* the view is updatable */ } /* * view_cols_are_auto_updatable - test whether all of the required columns of * an auto-updatable view are actually updatable. Returns NULL (if all the * required columns can be updated) or a message string giving the reason that * they cannot be. * * This should be used for INSERT/UPDATE to ensure that we don't attempt to * assign to any non-updatable columns. * * Additionally it may be used to retrieve the set of updatable columns in the * view, or if one or more of the required columns is not updatable, the name * of the first offending non-updatable column. * * The caller must have already verified that this is an auto-updatable view * using view_query_is_auto_updatable. * * Note that the checks performed here are only based on the view definition. * We do not check whether the referenced columns of the base relation are * updatable. */ static const char * view_cols_are_auto_updatable(Query *viewquery, Bitmapset *required_cols, Bitmapset **updatable_cols, char **non_updatable_col) { RangeTblRef *rtr; AttrNumber col; ListCell *cell; /* * The caller should have verified that this view is auto-updatable and * so there should be a single base relation. */ Assert(list_length(viewquery->jointree->fromlist) == 1); rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist); Assert(IsA(rtr, RangeTblRef)); /* Initialize the optional return values */ if (updatable_cols != NULL) *updatable_cols = NULL; if (non_updatable_col != NULL) *non_updatable_col = NULL; /* Test each view column for updatability */ col = -FirstLowInvalidHeapAttributeNumber; foreach(cell, viewquery->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(cell); const char *col_update_detail; col++; col_update_detail = view_col_is_auto_updatable(rtr, tle); if (col_update_detail == NULL) { /* The column is updatable */ if (updatable_cols != NULL) *updatable_cols = bms_add_member(*updatable_cols, col); } else if (bms_is_member(col, required_cols)) { /* The required column is not updatable */ if (non_updatable_col != NULL) *non_updatable_col = tle->resname; return col_update_detail; } } return NULL; /* all the required view columns are updatable */ } /* * relation_is_updatable - determine which update events the specified * relation supports. * * Note that views may contain a mix of updatable and non-updatable columns. * For a view to support INSERT/UPDATE it must have at least one updatable * column, but there is no such restriction for DELETE. If include_cols is * non-NULL, then only the specified columns are considered when testing for * updatability. * * This is used for the information_schema views, which have separate concepts * of "updatable" and "trigger updatable". A relation is "updatable" if it * can be updated without the need for triggers (either because it has a * suitable RULE, or because it is simple enough to be automatically updated). * A relation is "trigger updatable" if it has a suitable INSTEAD OF trigger. * The SQL standard regards this as not necessarily updatable, presumably * because there is no way of knowing what the trigger will actually do. * The information_schema views therefore call this function with * include_triggers = false. However, other callers might only care whether * data-modifying SQL will work, so they can pass include_triggers = true * to have trigger updatability included in the result. * * The return value is a bitmask of rule event numbers indicating which of * the INSERT, UPDATE and DELETE operations are supported. (We do it this way * so that we can test for UPDATE plus DELETE support in a single call.) */ int relation_is_updatable(Oid reloid, bool include_triggers, Bitmapset *include_cols) { int events = 0; Relation rel; RuleLock *rulelocks; #define ALL_EVENTS ((1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE)) rel = try_relation_open(reloid, AccessShareLock); /* * If the relation doesn't exist, return zero rather than throwing an * error. This is helpful since scanning an information_schema view under * MVCC rules can result in referencing rels that have actually been * deleted already. */ if (rel == NULL) return 0; /* If the relation is a table, it is always updatable */ if (rel->rd_rel->relkind == RELKIND_RELATION) { relation_close(rel, AccessShareLock); return ALL_EVENTS; } /* Look for unconditional DO INSTEAD rules, and note supported events */ rulelocks = rel->rd_rules; if (rulelocks != NULL) { int i; for (i = 0; i < rulelocks->numLocks; i++) { if (rulelocks->rules[i]->isInstead && rulelocks->rules[i]->qual == NULL) { events |= ((1 << rulelocks->rules[i]->event) & ALL_EVENTS); } } /* If we have rules for all events, we're done */ if (events == ALL_EVENTS) { relation_close(rel, AccessShareLock); return events; } } /* Similarly look for INSTEAD OF triggers, if they are to be included */ if (include_triggers) { TriggerDesc *trigDesc = rel->trigdesc; if (trigDesc) { if (trigDesc->trig_insert_instead_row) events |= (1 << CMD_INSERT); if (trigDesc->trig_update_instead_row) events |= (1 << CMD_UPDATE); if (trigDesc->trig_delete_instead_row) events |= (1 << CMD_DELETE); /* If we have triggers for all events, we're done */ if (events == ALL_EVENTS) { relation_close(rel, AccessShareLock); return events; } } } /* If this is a foreign table, check which update events it supports */ if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE) { FdwRoutine *fdwroutine = GetFdwRoutineForRelation(rel, false); if (fdwroutine->IsForeignRelUpdatable != NULL) events |= fdwroutine->IsForeignRelUpdatable(rel); else { /* Assume presence of executor functions is sufficient */ if (fdwroutine->ExecForeignInsert != NULL) events |= (1 << CMD_INSERT); if (fdwroutine->ExecForeignUpdate != NULL) events |= (1 << CMD_UPDATE); if (fdwroutine->ExecForeignDelete != NULL) events |= (1 << CMD_DELETE); } relation_close(rel, AccessShareLock); return events; } /* Check if this is an automatically updatable view */ if (rel->rd_rel->relkind == RELKIND_VIEW) { Query *viewquery = get_view_query(rel); if (view_query_is_auto_updatable(viewquery, RelationIsSecurityView(rel), false) == NULL) { Bitmapset *updatable_cols; int auto_events; RangeTblRef *rtr; RangeTblEntry *base_rte; Oid baseoid; /* * Determine which of the view's columns are updatable. If there * are none within the set of of columns we are looking at, then * the view doesn't support INSERT/UPDATE, but it may still * support DELETE. */ view_cols_are_auto_updatable(viewquery, NULL, &updatable_cols, NULL); if (include_cols != NULL) updatable_cols = bms_int_members(updatable_cols, include_cols); if (bms_is_empty(updatable_cols)) auto_events = (1 << CMD_DELETE); /* May support DELETE */ else auto_events = ALL_EVENTS; /* May support all events */ /* * The base relation must also support these update commands. * Tables are always updatable, but for any other kind of base * relation we must do a recursive check limited to the columns * referenced by the locally updatable columns in this view. */ rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist); base_rte = rt_fetch(rtr->rtindex, viewquery->rtable); Assert(base_rte->rtekind == RTE_RELATION); if (base_rte->relkind != RELKIND_RELATION) { baseoid = base_rte->relid; include_cols = adjust_view_column_set(updatable_cols, viewquery->targetList); auto_events &= relation_is_updatable(baseoid, include_triggers, include_cols); } events |= auto_events; } } /* If we reach here, the relation may support some update commands */ relation_close(rel, AccessShareLock); return events; } /* * adjust_view_column_set - map a set of column numbers according to targetlist * * This is used with simply-updatable views to map column-permissions sets for * the view columns onto the matching columns in the underlying base relation. * The targetlist is expected to be a list of plain Vars of the underlying * relation (as per the checks above in view_query_is_auto_updatable). */ static Bitmapset * adjust_view_column_set(Bitmapset *cols, List *targetlist) { Bitmapset *result = NULL; Bitmapset *tmpcols; AttrNumber col; tmpcols = bms_copy(cols); while ((col = bms_first_member(tmpcols)) >= 0) { /* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */ AttrNumber attno = col + FirstLowInvalidHeapAttributeNumber; if (attno == InvalidAttrNumber) { /* * There's a whole-row reference to the view. For permissions * purposes, treat it as a reference to each column available from * the view. (We should *not* convert this to a whole-row * reference to the base relation, since the view may not touch * all columns of the base relation.) */ ListCell *lc; foreach(lc, targetlist) { TargetEntry *tle = (TargetEntry *) lfirst(lc); Var *var; if (tle->resjunk) continue; var = (Var *) tle->expr; Assert(IsA(var, Var)); result = bms_add_member(result, var->varattno - FirstLowInvalidHeapAttributeNumber); } } else { /* * Views do not have system columns, so we do not expect to see * any other system attnos here. If we do find one, the error * case will apply. */ TargetEntry *tle = get_tle_by_resno(targetlist, attno); if (tle != NULL && !tle->resjunk && IsA(tle->expr, Var)) { Var *var = (Var *) tle->expr; result = bms_add_member(result, var->varattno - FirstLowInvalidHeapAttributeNumber); } else elog(ERROR, "attribute number %d not found in view targetlist", attno); } } bms_free(tmpcols); return result; } /* * rewriteTargetView - * Attempt to rewrite a query where the target relation is a view, so that * the view's base relation becomes the target relation. * * Note that the base relation here may itself be a view, which may or may not * have INSTEAD OF triggers or rules to handle the update. That is handled by * the recursion in RewriteQuery. */ static Query * rewriteTargetView(Query *parsetree, Relation view) { Query *viewquery; const char *auto_update_detail; RangeTblRef *rtr; int base_rt_index; int new_rt_index; RangeTblEntry *base_rte; RangeTblEntry *view_rte; RangeTblEntry *new_rte; Relation base_rel; List *view_targetlist; ListCell *lc; /* The view must be updatable, else fail */ viewquery = get_view_query(view); auto_update_detail = view_query_is_auto_updatable(viewquery, RelationIsSecurityView(view), parsetree->commandType != CMD_DELETE); if (auto_update_detail) { /* messages here should match execMain.c's CheckValidResultRel */ switch (parsetree->commandType) { case CMD_INSERT: ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("cannot insert into view \"%s\"", RelationGetRelationName(view)), errdetail_internal("%s", _(auto_update_detail)), errhint("To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule."))); break; case CMD_UPDATE: ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("cannot update view \"%s\"", RelationGetRelationName(view)), errdetail_internal("%s", _(auto_update_detail)), errhint("To enable updating the view, provide an INSTEAD OF UPDATE trigger or an unconditional ON UPDATE DO INSTEAD rule."))); break; case CMD_DELETE: ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("cannot delete from view \"%s\"", RelationGetRelationName(view)), errdetail_internal("%s", _(auto_update_detail)), errhint("To enable deleting from the view, provide an INSTEAD OF DELETE trigger or an unconditional ON DELETE DO INSTEAD rule."))); break; default: elog(ERROR, "unrecognized CmdType: %d", (int) parsetree->commandType); break; } } /* * For INSERT/UPDATE the modified columns must all be updatable. Note that * we get the modified columns from the query's targetlist, not from the * result RTE's modifiedCols set, since rewriteTargetListIU may have added * additional targetlist entries for view defaults, and these must also be * updatable. */ if (parsetree->commandType != CMD_DELETE) { Bitmapset *modified_cols = NULL; char *non_updatable_col; foreach(lc, parsetree->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(lc); if (!tle->resjunk) modified_cols = bms_add_member(modified_cols, tle->resno - FirstLowInvalidHeapAttributeNumber); } auto_update_detail = view_cols_are_auto_updatable(viewquery, modified_cols, NULL, &non_updatable_col); if (auto_update_detail) { /* * This is a different error, caused by an attempt to update a * non-updatable column in an otherwise updatable view. */ switch (parsetree->commandType) { case CMD_INSERT: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot insert into column \"%s\" of view \"%s\"", non_updatable_col, RelationGetRelationName(view)), errdetail_internal("%s", _(auto_update_detail)))); break; case CMD_UPDATE: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot update column \"%s\" of view \"%s\"", non_updatable_col, RelationGetRelationName(view)), errdetail_internal("%s", _(auto_update_detail)))); break; default: elog(ERROR, "unrecognized CmdType: %d", (int) parsetree->commandType); break; } } } /* Locate RTE describing the view in the outer query */ view_rte = rt_fetch(parsetree->resultRelation, parsetree->rtable); /* * If we get here, view_query_is_auto_updatable() has verified that the * view contains a single base relation. */ Assert(list_length(viewquery->jointree->fromlist) == 1); rtr = (RangeTblRef *) linitial(viewquery->jointree->fromlist); Assert(IsA(rtr, RangeTblRef)); base_rt_index = rtr->rtindex; base_rte = rt_fetch(base_rt_index, viewquery->rtable); Assert(base_rte->rtekind == RTE_RELATION); /* * Up to now, the base relation hasn't been touched at all in our query. * We need to acquire lock on it before we try to do anything with it. * (The subsequent recursive call of RewriteQuery will suppose that we * already have the right lock!) Since it will become the query target * relation, RowExclusiveLock is always the right thing. */ base_rel = heap_open(base_rte->relid, RowExclusiveLock); /* * While we have the relation open, update the RTE's relkind, just in case * it changed since this view was made (cf. AcquireRewriteLocks). */ base_rte->relkind = base_rel->rd_rel->relkind; heap_close(base_rel, NoLock); /* * Create a new target RTE describing the base relation, and add it to the * outer query's rangetable. (What's happening in the next few steps is * very much like what the planner would do to "pull up" the view into the * outer query. Perhaps someday we should refactor things enough so that * we can share code with the planner.) */ new_rte = (RangeTblEntry *) copyObject(base_rte); parsetree->rtable = lappend(parsetree->rtable, new_rte); new_rt_index = list_length(parsetree->rtable); /* * INSERTs never inherit. For UPDATE/DELETE, we use the view query's * inheritance flag for the base relation. */ if (parsetree->commandType == CMD_INSERT) new_rte->inh = false; /* * Make a copy of the view's targetlist, adjusting its Vars to reference * the new target RTE, ie make their varnos be new_rt_index instead of * base_rt_index. There can be no Vars for other rels in the tlist, so * this is sufficient to pull up the tlist expressions for use in the * outer query. The tlist will provide the replacement expressions used * by ReplaceVarsFromTargetList below. */ view_targetlist = copyObject(viewquery->targetList); ChangeVarNodes((Node *) view_targetlist, base_rt_index, new_rt_index, 0); /* * Mark the new target RTE for the permissions checks that we want to * enforce against the view owner, as distinct from the query caller. At * the relation level, require the same INSERT/UPDATE/DELETE permissions * that the query caller needs against the view. We drop the ACL_SELECT * bit that is presumably in new_rte->requiredPerms initially. * * Note: the original view RTE remains in the query's rangetable list. * Although it will be unused in the query plan, we need it there so that * the executor still performs appropriate permissions checks for the * query caller's use of the view. */ new_rte->checkAsUser = view->rd_rel->relowner; new_rte->requiredPerms = view_rte->requiredPerms; /* * Now for the per-column permissions bits. * * Initially, new_rte contains selectedCols permission check bits for all * base-rel columns referenced by the view, but since the view is a SELECT * query its modifiedCols is empty. We set modifiedCols to include all * the columns the outer query is trying to modify, adjusting the column * numbers as needed. But we leave selectedCols as-is, so the view owner * must have read permission for all columns used in the view definition, * even if some of them are not read by the outer query. We could try to * limit selectedCols to only columns used in the transformed query, but * that does not correspond to what happens in ordinary SELECT usage of a * view: all referenced columns must have read permission, even if * optimization finds that some of them can be discarded during query * transformation. The flattening we're doing here is an optional * optimization, too. (If you are unpersuaded and want to change this, * note that applying adjust_view_column_set to view_rte->selectedCols is * clearly *not* the right answer, since that neglects base-rel columns * used in the view's WHERE quals.) * * This step needs the modified view targetlist, so we have to do things * in this order. */ Assert(bms_is_empty(new_rte->modifiedCols)); new_rte->modifiedCols = adjust_view_column_set(view_rte->modifiedCols, view_targetlist); /* * For UPDATE/DELETE, rewriteTargetListUD will have added a wholerow junk * TLE for the view to the end of the targetlist, which we no longer need. * Remove it to avoid unnecessary work when we process the targetlist. * Note that when we recurse through rewriteQuery a new junk TLE will be * added to allow the executor to find the proper row in the new target * relation. (So, if we failed to do this, we might have multiple junk * TLEs with the same name, which would be disastrous.) */ if (parsetree->commandType != CMD_INSERT) { TargetEntry *tle = (TargetEntry *) llast(parsetree->targetList); Assert(tle->resjunk); Assert(IsA(tle->expr, Var) && ((Var *) tle->expr)->varno == parsetree->resultRelation && ((Var *) tle->expr)->varattno == 0); parsetree->targetList = list_delete_ptr(parsetree->targetList, tle); } /* * Now update all Vars in the outer query that reference the view to * reference the appropriate column of the base relation instead. */ parsetree = (Query *) ReplaceVarsFromTargetList((Node *) parsetree, parsetree->resultRelation, 0, view_rte, view_targetlist, REPLACEVARS_REPORT_ERROR, 0, &parsetree->hasSubLinks); /* * Update all other RTI references in the query that point to the view * (for example, parsetree->resultRelation itself) to point to the new * base relation instead. Vars will not be affected since none of them * reference parsetree->resultRelation any longer. */ ChangeVarNodes((Node *) parsetree, parsetree->resultRelation, new_rt_index, 0); Assert(parsetree->resultRelation == new_rt_index); /* * For INSERT/UPDATE we must also update resnos in the targetlist to refer * to columns of the base relation, since those indicate the target * columns to be affected. * * Note that this destroys the resno ordering of the targetlist, but that * will be fixed when we recurse through rewriteQuery, which will invoke * rewriteTargetListIU again on the updated targetlist. */ if (parsetree->commandType != CMD_DELETE) { foreach(lc, parsetree->targetList) { TargetEntry *tle = (TargetEntry *) lfirst(lc); TargetEntry *view_tle; if (tle->resjunk) continue; view_tle = get_tle_by_resno(view_targetlist, tle->resno); if (view_tle != NULL && !view_tle->resjunk && IsA(view_tle->expr, Var)) tle->resno = ((Var *) view_tle->expr)->varattno; else elog(ERROR, "attribute number %d not found in view targetlist", tle->resno); } } /* * For UPDATE/DELETE, pull up any WHERE quals from the view. We know that * any Vars in the quals must reference the one base relation, so we need * only adjust their varnos to reference the new target (just the same as * we did with the view targetlist). * * For INSERT, the view's quals can be ignored in the main query. */ if (parsetree->commandType != CMD_INSERT && viewquery->jointree->quals != NULL) { Node *viewqual = (Node *) copyObject(viewquery->jointree->quals); ChangeVarNodes(viewqual, base_rt_index, new_rt_index, 0); AddQual(parsetree, (Node *) viewqual); } /* * For INSERT/UPDATE, if the view has the WITH CHECK OPTION, or any parent * view specified WITH CASCADED CHECK OPTION, add the quals from the view * to the query's withCheckOptions list. */ if (parsetree->commandType != CMD_DELETE) { bool has_wco = RelationHasCheckOption(view); bool cascaded = RelationHasCascadedCheckOption(view); /* * If the parent view has a cascaded check option, treat this view as * if it also had a cascaded check option. * * New WithCheckOptions are added to the start of the list, so if there * is a cascaded check option, it will be the first item in the list. */ if (parsetree->withCheckOptions != NIL) { WithCheckOption *parent_wco = (WithCheckOption *) linitial(parsetree->withCheckOptions); if (parent_wco->cascaded) { has_wco = true; cascaded = true; } } /* * Add the new WithCheckOption to the start of the list, so that * checks on inner views are run before checks on outer views, as * required by the SQL standard. * * If the new check is CASCADED, we need to add it even if this view * has no quals, since there may be quals on child views. A LOCAL * check can be omitted if this view has no quals. */ if (has_wco && (cascaded || viewquery->jointree->quals != NULL)) { WithCheckOption *wco; wco = makeNode(WithCheckOption); wco->viewname = pstrdup(RelationGetRelationName(view)); wco->qual = NULL; wco->cascaded = cascaded; parsetree->withCheckOptions = lcons(wco, parsetree->withCheckOptions); if (viewquery->jointree->quals != NULL) { wco->qual = (Node *) copyObject(viewquery->jointree->quals); ChangeVarNodes(wco->qual, base_rt_index, new_rt_index, 0); /* * Make sure that the query is marked correctly if the added * qual has sublinks. We can skip this check if the query is * already marked, or if the command is an UPDATE, in which * case the same qual will have already been added to the * query's WHERE clause, and AddQual will have already done * this check. */ if (!parsetree->hasSubLinks && parsetree->commandType != CMD_UPDATE) parsetree->hasSubLinks = checkExprHasSubLink(wco->qual); } } } return parsetree; } /* * 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; bool returning = false; Query *qual_product = NULL; List *rewritten = NIL; ListCell *lc1; /* * First, recursively process any insert/update/delete statements in WITH * clauses. (We have to do this first because the WITH clauses may get * copied into rule actions below.) */ foreach(lc1, parsetree->cteList) { CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc1); Query *ctequery = (Query *) cte->ctequery; List *newstuff; Assert(IsA(ctequery, Query)); if (ctequery->commandType == CMD_SELECT) continue; newstuff = RewriteQuery(ctequery, rewrite_events); /* * Currently we can only handle unconditional, single-statement DO * INSTEAD rules correctly; we have to get exactly one Query out of * the rewrite operation to stuff back into the CTE node. */ if (list_length(newstuff) == 1) { /* Push the single Query back into the CTE node */ ctequery = (Query *) linitial(newstuff); Assert(IsA(ctequery, Query)); /* WITH queries should never be canSetTag */ Assert(!ctequery->canSetTag); cte->ctequery = (Node *) ctequery; } else if (newstuff == NIL) { ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("DO INSTEAD NOTHING rules are not supported for data-modifying statements in WITH"))); } else { ListCell *lc2; /* examine queries to determine which error message to issue */ foreach(lc2, newstuff) { Query *q = (Query *) lfirst(lc2); if (q->querySource == QSRC_QUAL_INSTEAD_RULE) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("conditional DO INSTEAD rules are not supported for data-modifying statements in WITH"))); if (q->querySource == QSRC_NON_INSTEAD_RULE) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("DO ALSO rules are not supported for data-modifying statements in WITH"))); } ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("multi-statement DO INSTEAD rules are not supported for data-modifying statements in WITH"))); } } /* * If the statement is an insert, update, or delete, adjust its targetlist * as needed, and then fire INSERT/UPDATE/DELETE 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; List *product_queries; 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); /* * Rewrite the targetlist as needed for the command type. */ 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 ... */ rewriteTargetListIU(parsetree, rt_entry_relation, &attrnos); /* ... and the VALUES expression lists */ rewriteValuesRTE(values_rte, rt_entry_relation, attrnos); } else { /* Process just the main targetlist */ rewriteTargetListIU(parsetree, rt_entry_relation, NULL); } } else if (event == CMD_UPDATE) { rewriteTargetListIU(parsetree, rt_entry_relation, NULL); rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation); } else if (event == CMD_DELETE) { rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation); } else elog(ERROR, "unrecognized commandType: %d", (int) event); /* * Collect and apply the appropriate rules. */ locks = matchLocks(event, rt_entry_relation->rd_rules, result_relation, parsetree); product_queries = fireRules(parsetree, result_relation, event, locks, &instead, &returning, &qual_product); /* * If there were no INSTEAD rules, and the target relation is a view * without any INSTEAD OF triggers, see if the view can be * automatically updated. If so, we perform the necessary query * transformation here and add the resulting query to the * product_queries list, so that it gets recursively rewritten if * necessary. */ if (!instead && qual_product == NULL && rt_entry_relation->rd_rel->relkind == RELKIND_VIEW && !view_has_instead_trigger(rt_entry_relation, event)) { /* * This throws an error if the view can't be automatically * updated, but that's OK since the query would fail at runtime * anyway. */ parsetree = rewriteTargetView(parsetree, rt_entry_relation); /* * At this point product_queries contains any DO ALSO rule * actions. Add the rewritten query before or after those. This * must match the handling the original query would have gotten * below, if we allowed it to be included again. */ if (parsetree->commandType == CMD_INSERT) product_queries = lcons(parsetree, product_queries); else product_queries = lappend(product_queries, parsetree); /* * Set the "instead" flag, as if there had been an unqualified * INSTEAD, to prevent the original query from being included a * second time below. The transformation will have rewritten any * RETURNING list, so we can also set "returning" to forestall * throwing an error below. */ instead = true; returning = true; } /* * 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); } /* * If there is an INSTEAD, and the original query has a RETURNING, we * have to have found a RETURNING in the rule(s), else fail. (Because * DefineQueryRewrite only allows RETURNING in unconditional INSTEAD * rules, there's no need to worry whether the substituted RETURNING * will actually be executed --- it must be.) */ if ((instead || qual_product != NULL) && parsetree->returningList && !returning) { switch (event) { case CMD_INSERT: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot perform INSERT RETURNING on relation \"%s\"", RelationGetRelationName(rt_entry_relation)), errhint("You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause."))); break; case CMD_UPDATE: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot perform UPDATE RETURNING on relation \"%s\"", RelationGetRelationName(rt_entry_relation)), errhint("You need an unconditional ON UPDATE DO INSTEAD rule with a RETURNING clause."))); break; case CMD_DELETE: ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("cannot perform DELETE RETURNING on relation \"%s\"", RelationGetRelationName(rt_entry_relation)), errhint("You need an unconditional ON DELETE DO INSTEAD rule with a RETURNING clause."))); break; default: elog(ERROR, "unrecognized commandType: %d", (int) event); break; } } 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); } } /* * If the original query has a CTE list, and we generated more than one * non-utility result query, we have to fail because we'll have copied the * CTE list into each result query. That would break the expectation of * single evaluation of CTEs. This could possibly be fixed by * restructuring so that a CTE list can be shared across multiple Query * and PlannableStatement nodes. */ if (parsetree->cteList != NIL) { int qcount = 0; foreach(lc1, rewritten) { Query *q = (Query *) lfirst(lc1); if (q->commandType != CMD_UTILITY) qcount++; } if (qcount > 1) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("WITH cannot be used in a query that is rewritten by rules into multiple queries"))); } 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) { uint32 input_query_id = parsetree->queryId; List *querylist; List *results; ListCell *l; CmdType origCmdType; bool foundOriginalQuery; Query *lastInstead; /* * This function is only applied to top-level original queries */ Assert(parsetree->querySource == QSRC_ORIGINAL); Assert(parsetree->canSetTag); /* * 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 * * This is also a handy place to mark each query with the original queryId */ results = NIL; foreach(l, querylist) { Query *query = (Query *) lfirst(l); query = fireRIRrules(query, NIL, false); query->queryId = input_query_id; 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; }