/*------------------------------------------------------------------------- * * view.c * use rewrite rules to construct views * * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/commands/view.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "access/heapam.h" #include "access/xact.h" #include "catalog/namespace.h" #include "commands/defrem.h" #include "commands/tablecmds.h" #include "commands/view.h" #include "miscadmin.h" #include "nodes/makefuncs.h" #include "nodes/nodeFuncs.h" #include "parser/analyze.h" #include "parser/parse_relation.h" #include "rewrite/rewriteDefine.h" #include "rewrite/rewriteManip.h" #include "rewrite/rewriteHandler.h" #include "rewrite/rewriteSupport.h" #include "utils/acl.h" #include "utils/builtins.h" #include "utils/lsyscache.h" #include "utils/rel.h" #include "utils/syscache.h" static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc); /*--------------------------------------------------------------------- * Validator for "check_option" reloption on views. The allowed values * are "local" and "cascaded". */ void validateWithCheckOption(char *value) { if (value == NULL || (pg_strcasecmp(value, "local") != 0 && pg_strcasecmp(value, "cascaded") != 0)) { ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("invalid value for \"check_option\" option"), errdetail("Valid values are \"local\" and \"cascaded\"."))); } } /*--------------------------------------------------------------------- * DefineVirtualRelation * * Create the "view" relation. `DefineRelation' does all the work, * we just provide the correct arguments ... at least when we're * creating a view. If we're updating an existing view, we have to * work harder. *--------------------------------------------------------------------- */ static ObjectAddress DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace, List *options) { Oid viewOid; LOCKMODE lockmode; CreateStmt *createStmt = makeNode(CreateStmt); List *attrList; ListCell *t; /* * create a list of ColumnDef nodes based on the names and types of the * (non-junk) targetlist items from the view's SELECT list. */ attrList = NIL; foreach(t, tlist) { TargetEntry *tle = lfirst(t); if (!tle->resjunk) { ColumnDef *def = makeNode(ColumnDef); def->colname = pstrdup(tle->resname); def->typeName = makeTypeNameFromOid(exprType((Node *) tle->expr), exprTypmod((Node *) tle->expr)); def->inhcount = 0; def->is_local = true; def->is_not_null = false; def->is_from_type = false; def->storage = 0; def->raw_default = NULL; def->cooked_default = NULL; def->collClause = NULL; def->collOid = exprCollation((Node *) tle->expr); def->location = -1; /* * It's possible that the column is of a collatable type but the * collation could not be resolved, so double-check. */ if (type_is_collatable(exprType((Node *) tle->expr))) { if (!OidIsValid(def->collOid)) ereport(ERROR, (errcode(ERRCODE_INDETERMINATE_COLLATION), errmsg("could not determine which collation to use for view column \"%s\"", def->colname), errhint("Use the COLLATE clause to set the collation explicitly."))); } else Assert(!OidIsValid(def->collOid)); def->constraints = NIL; attrList = lappend(attrList, def); } } if (attrList == NIL) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("view must have at least one column"))); /* * Look up, check permissions on, and lock the creation namespace; also * check for a preexisting view with the same name. This will also set * relation->relpersistence to RELPERSISTENCE_TEMP if the selected * namespace is temporary. */ lockmode = replace ? AccessExclusiveLock : NoLock; (void) RangeVarGetAndCheckCreationNamespace(relation, lockmode, &viewOid); if (OidIsValid(viewOid) && replace) { Relation rel; TupleDesc descriptor; List *atcmds = NIL; AlterTableCmd *atcmd; ObjectAddress address; /* Relation is already locked, but we must build a relcache entry. */ rel = relation_open(viewOid, NoLock); /* Make sure it *is* a view. */ if (rel->rd_rel->relkind != RELKIND_VIEW) ereport(ERROR, (errcode(ERRCODE_WRONG_OBJECT_TYPE), errmsg("\"%s\" is not a view", RelationGetRelationName(rel)))); /* Also check it's not in use already */ CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW"); /* * Due to the namespace visibility rules for temporary objects, we * should only end up replacing a temporary view with another * temporary view, and similarly for permanent views. */ Assert(relation->relpersistence == rel->rd_rel->relpersistence); /* * Create a tuple descriptor to compare against the existing view, and * verify that the old column list is an initial prefix of the new * column list. */ descriptor = BuildDescForRelation(attrList); checkViewTupleDesc(descriptor, rel->rd_att); /* * The new options list replaces the existing options list, even if * it's empty. */ atcmd = makeNode(AlterTableCmd); atcmd->subtype = AT_ReplaceRelOptions; atcmd->def = (Node *) options; atcmds = lappend(atcmds, atcmd); /* * If new attributes have been added, we must add pg_attribute entries * for them. It is convenient (although overkill) to use the ALTER * TABLE ADD COLUMN infrastructure for this. */ if (list_length(attrList) > rel->rd_att->natts) { ListCell *c; int skip = rel->rd_att->natts; foreach(c, attrList) { if (skip > 0) { skip--; continue; } atcmd = makeNode(AlterTableCmd); atcmd->subtype = AT_AddColumnToView; atcmd->def = (Node *) lfirst(c); atcmds = lappend(atcmds, atcmd); } } /* OK, let's do it. */ AlterTableInternal(viewOid, atcmds, true); ObjectAddressSet(address, RelationRelationId, viewOid); /* * Seems okay, so return the OID of the pre-existing view. */ relation_close(rel, NoLock); /* keep the lock! */ return address; } else { ObjectAddress address; /* * now set the parameters for keys/inheritance etc. All of these are * uninteresting for views... */ createStmt->relation = relation; createStmt->tableElts = attrList; createStmt->inhRelations = NIL; createStmt->constraints = NIL; createStmt->options = options; createStmt->oncommit = ONCOMMIT_NOOP; createStmt->tablespacename = NULL; createStmt->if_not_exists = false; /* * finally create the relation (this will error out if there's an * existing view, so we don't need more code to complain if "replace" * is false). */ address = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid, NULL); Assert(address.objectId != InvalidOid); return address; } } /* * Verify that tupledesc associated with proposed new view definition * matches tupledesc of old view. This is basically a cut-down version * of equalTupleDescs(), with code added to generate specific complaints. * Also, we allow the new tupledesc to have more columns than the old. */ static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc) { int i; if (newdesc->natts < olddesc->natts) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot drop columns from view"))); /* we can ignore tdhasoid */ for (i = 0; i < olddesc->natts; i++) { Form_pg_attribute newattr = newdesc->attrs[i]; Form_pg_attribute oldattr = olddesc->attrs[i]; /* XXX msg not right, but we don't support DROP COL on view anyway */ if (newattr->attisdropped != oldattr->attisdropped) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot drop columns from view"))); if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change name of view column \"%s\" to \"%s\"", NameStr(oldattr->attname), NameStr(newattr->attname)))); /* XXX would it be safe to allow atttypmod to change? Not sure */ if (newattr->atttypid != oldattr->atttypid || newattr->atttypmod != oldattr->atttypmod) ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION), errmsg("cannot change data type of view column \"%s\" from %s to %s", NameStr(oldattr->attname), format_type_with_typemod(oldattr->atttypid, oldattr->atttypmod), format_type_with_typemod(newattr->atttypid, newattr->atttypmod)))); /* We can ignore the remaining attributes of an attribute... */ } /* * We ignore the constraint fields. The new view desc can't have any * constraints, and the only ones that could be on the old view are * defaults, which we are happy to leave in place. */ } static void DefineViewRules(Oid viewOid, Query *viewParse, bool replace) { /* * Set up the ON SELECT rule. Since the query has already been through * parse analysis, we use DefineQueryRewrite() directly. */ DefineQueryRewrite(pstrdup(ViewSelectRuleName), viewOid, NULL, CMD_SELECT, true, replace, list_make1(viewParse)); /* * Someday: automatic ON INSERT, etc */ } /*--------------------------------------------------------------- * UpdateRangeTableOfViewParse * * Update the range table of the given parsetree. * This update consists of adding two new entries IN THE BEGINNING * of the range table (otherwise the rule system will die a slow, * horrible and painful death, and we do not want that now, do we?) * one for the OLD relation and one for the NEW one (both of * them refer in fact to the "view" relation). * * Of course we must also increase the 'varnos' of all the Var nodes * by 2... * * These extra RT entries are not actually used in the query, * except for run-time permission checking. *--------------------------------------------------------------- */ static Query * UpdateRangeTableOfViewParse(Oid viewOid, Query *viewParse) { Relation viewRel; List *new_rt; RangeTblEntry *rt_entry1, *rt_entry2; ParseState *pstate; /* * Make a copy of the given parsetree. It's not so much that we don't * want to scribble on our input, it's that the parser has a bad habit of * outputting multiple links to the same subtree for constructs like * BETWEEN, and we mustn't have OffsetVarNodes increment the varno of a * Var node twice. copyObject will expand any multiply-referenced subtree * into multiple copies. */ viewParse = (Query *) copyObject(viewParse); /* Create a dummy ParseState for addRangeTableEntryForRelation */ pstate = make_parsestate(NULL); /* need to open the rel for addRangeTableEntryForRelation */ viewRel = relation_open(viewOid, AccessShareLock); /* * Create the 2 new range table entries and form the new range table... * OLD first, then NEW.... */ rt_entry1 = addRangeTableEntryForRelation(pstate, viewRel, makeAlias("old", NIL), false, false); rt_entry2 = addRangeTableEntryForRelation(pstate, viewRel, makeAlias("new", NIL), false, false); /* Must override addRangeTableEntry's default access-check flags */ rt_entry1->requiredPerms = 0; rt_entry2->requiredPerms = 0; new_rt = lcons(rt_entry1, lcons(rt_entry2, viewParse->rtable)); viewParse->rtable = new_rt; /* * Now offset all var nodes by 2, and jointree RT indexes too. */ OffsetVarNodes((Node *) viewParse, 2, 0); relation_close(viewRel, AccessShareLock); return viewParse; } /* * DefineView * Execute a CREATE VIEW command. */ ObjectAddress DefineView(ViewStmt *stmt, const char *queryString) { Query *viewParse; RangeVar *view; ListCell *cell; bool check_option; ObjectAddress address; /* * Run parse analysis to convert the raw parse tree to a Query. Note this * also acquires sufficient locks on the source table(s). * * Since parse analysis scribbles on its input, copy the raw parse tree; * this ensures we don't corrupt a prepared statement, for example. */ viewParse = parse_analyze((Node *) copyObject(stmt->query), queryString, NULL, 0); /* * The grammar should ensure that the result is a single SELECT Query. * However, it doesn't forbid SELECT INTO, so we have to check for that. */ if (!IsA(viewParse, Query)) elog(ERROR, "unexpected parse analysis result"); if (viewParse->utilityStmt != NULL && IsA(viewParse->utilityStmt, CreateTableAsStmt)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain SELECT INTO"))); if (viewParse->commandType != CMD_SELECT || viewParse->utilityStmt != NULL) elog(ERROR, "unexpected parse analysis result"); /* * Check for unsupported cases. These tests are redundant with ones in * DefineQueryRewrite(), but that function will complain about a bogus ON * SELECT rule, and we'd rather the message complain about a view. */ if (viewParse->hasModifyingCTE) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("views must not contain data-modifying statements in WITH"))); /* * If the user specified the WITH CHECK OPTION, add it to the list of * reloptions. */ if (stmt->withCheckOption == LOCAL_CHECK_OPTION) stmt->options = lappend(stmt->options, makeDefElem("check_option", (Node *) makeString("local"))); else if (stmt->withCheckOption == CASCADED_CHECK_OPTION) stmt->options = lappend(stmt->options, makeDefElem("check_option", (Node *) makeString("cascaded"))); /* * Check that the view is auto-updatable if WITH CHECK OPTION was * specified. */ check_option = false; foreach(cell, stmt->options) { DefElem *defel = (DefElem *) lfirst(cell); if (pg_strcasecmp(defel->defname, "check_option") == 0) check_option = true; } /* * If the check option is specified, look to see if the view is actually * auto-updatable or not. */ if (check_option) { const char *view_updatable_error = view_query_is_auto_updatable(viewParse, true); if (view_updatable_error) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("WITH CHECK OPTION is supported only on automatically updatable views"), errhint("%s", view_updatable_error))); } /* * If a list of column names was given, run through and insert these into * the actual query tree. - thomas 2000-03-08 */ if (stmt->aliases != NIL) { ListCell *alist_item = list_head(stmt->aliases); ListCell *targetList; foreach(targetList, viewParse->targetList) { TargetEntry *te = (TargetEntry *) lfirst(targetList); Assert(IsA(te, TargetEntry)); /* junk columns don't get aliases */ if (te->resjunk) continue; te->resname = pstrdup(strVal(lfirst(alist_item))); alist_item = lnext(alist_item); if (alist_item == NULL) break; /* done assigning aliases */ } if (alist_item != NULL) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("CREATE VIEW specifies more column " "names than columns"))); } /* Unlogged views are not sensible. */ if (stmt->view->relpersistence == RELPERSISTENCE_UNLOGGED) ereport(ERROR, (errcode(ERRCODE_SYNTAX_ERROR), errmsg("views cannot be unlogged because they do not have storage"))); /* * If the user didn't explicitly ask for a temporary view, check whether * we need one implicitly. We allow TEMP to be inserted automatically as * long as the CREATE command is consistent with that --- no explicit * schema name. */ view = copyObject(stmt->view); /* don't corrupt original command */ if (view->relpersistence == RELPERSISTENCE_PERMANENT && isQueryUsingTempRelation(viewParse)) { view->relpersistence = RELPERSISTENCE_TEMP; ereport(NOTICE, (errmsg("view \"%s\" will be a temporary view", view->relname))); } /* * Create the view relation * * NOTE: if it already exists and replace is false, the xact will be * aborted. */ address = DefineVirtualRelation(view, viewParse->targetList, stmt->replace, stmt->options); /* * The relation we have just created is not visible to any other commands * running with the same transaction & command id. So, increment the * command id counter (but do NOT pfree any memory!!!!) */ CommandCounterIncrement(); StoreViewQuery(address.objectId, viewParse, stmt->replace); return address; } /* * Use the rules system to store the query for the view. */ void StoreViewQuery(Oid viewOid, Query *viewParse, bool replace) { /* * The range table of 'viewParse' does not contain entries for the "OLD" * and "NEW" relations. So... add them! */ viewParse = UpdateRangeTableOfViewParse(viewOid, viewParse); /* * Now create the rules associated with the view. */ DefineViewRules(viewOid, viewParse, replace); }