/*-------------------------------------------------------------------------
*
* view.c
* use rewrite rules to construct views
*
* Portions Copyright (c) 1996-2019, 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(const char *value)
{
if (value == NULL ||
(strcmp(value, "local") != 0 &&
strcmp(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 a view relation and use the rules system to store the query
* for the view.
*
* EventTriggerAlterTableStart must have been called already.
*---------------------------------------------------------------------
*/
static ObjectAddress
DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
List *options, Query *viewParse)
{
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 = (TargetEntry *) lfirst(t);
if (!tle->resjunk)
{
ColumnDef *def = makeColumnDef(tle->resname,
exprType((Node *) tle->expr),
exprTypmod((Node *) tle->expr),
exprCollation((Node *) tle->expr));
/*
* 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));
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);
/*
* 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.
*
* Note that we must do this before updating the query for the view,
* since the rules system requires that the correct view columns be in
* place when defining the new rules.
*/
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);
}
/* EventTriggerAlterTableStart called by ProcessUtilitySlow */
AlterTableInternal(viewOid, atcmds, true);
/* Make the new view columns visible */
CommandCounterIncrement();
}
/*
* Update the query for the view.
*
* Note that we must do this before updating the view options, because
* the new options may not be compatible with the old view query (for
* example if we attempt to add the WITH CHECK OPTION, we require that
* the new view be automatically updatable, but the old view may not
* have been).
*/
StoreViewQuery(viewOid, viewParse, replace);
/* Make the new view query visible */
CommandCounterIncrement();
/*
* Finally update the view options.
*
* 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 = list_make1(atcmd);
/* EventTriggerAlterTableStart called by ProcessUtilitySlow */
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;
/*
* 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;
/*
* 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,
NULL);
Assert(address.objectId != InvalidOid);
/* Make the new view relation visible */
CommandCounterIncrement();
/* Store the query for the view */
StoreViewQuery(address.objectId, viewParse, replace);
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")));
for (i = 0; i < olddesc->natts; i++)
{
Form_pg_attribute newattr = TupleDescAttr(newdesc, i);
Form_pg_attribute oldattr = TupleDescAttr(olddesc, 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 locking and 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 = 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,
AccessShareLock,
makeAlias("old", NIL),
false, false);
rt_entry2 = addRangeTableEntryForRelation(pstate, viewRel,
AccessShareLock,
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,
int stmt_location, int stmt_len)
{
RawStmt *rawstmt;
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.
*/
rawstmt = makeNode(RawStmt);
rawstmt->stmt = (Node *) copyObject(stmt->query);
rawstmt->stmt_location = stmt_location;
rawstmt->stmt_len = stmt_len;
viewParse = parse_analyze(rawstmt, queryString, NULL, 0, NULL);
/*
* 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)
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"), -1));
else if (stmt->withCheckOption == CASCADED_CHECK_OPTION)
stmt->options = lappend(stmt->options,
makeDefElem("check_option",
(Node *) makeString("cascaded"), -1));
/*
* 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 (strcmp(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 = lfirst_node(TargetEntry, targetList);
/* 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, viewParse);
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);
}