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Kevin Grittner authored
A materialized view has a rule just like a view and a heap and other physical properties like a table. The rule is only used to populate the table, references in queries refer to the materialized data. This is a minimal implementation, but should still be useful in many cases. Currently data is only populated "on demand" by the CREATE MATERIALIZED VIEW and REFRESH MATERIALIZED VIEW statements. It is expected that future releases will add incremental updates with various timings, and that a more refined concept of defining what is "fresh" data will be developed. At some point it may even be possible to have queries use a materialized in place of references to underlying tables, but that requires the other above-mentioned features to be working first. Much of the documentation work by Robert Haas. Review by Noah Misch, Thom Brown, Robert Haas, Marko Tiikkaja Security review by KaiGai Kohei, with a decision on how best to implement sepgsql still pending.
view.c 14.75 KiB
/*-------------------------------------------------------------------------
*
* view.c
* use rewrite rules to construct views
*
* Portions Copyright (c) 1996-2013, 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/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);
/*---------------------------------------------------------------------
* 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 Oid
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);
/*
* 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;
/* 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);
/*
* Seems okay, so return the OID of the pre-existing view.
*/
relation_close(rel, NoLock); /* keep the lock! */
return viewOid;
}
else
{
Oid relid;
/*
* 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->options = lappend(options, defWithOids(false));
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).
*/
relid = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid);
Assert(relid != InvalidOid);
return relid;
}
}
/*
* 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;
/*
* 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);
/* 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(NULL, viewRel,
makeAlias("old", NIL),
false, false);
rt_entry2 = addRangeTableEntryForRelation(NULL, 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.
*/
Oid
DefineView(ViewStmt *stmt, const char *queryString)
{
Query *viewParse;
Oid viewOid;
RangeVar *view;
/*
* 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 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.
*/
viewOid = 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(viewOid, viewParse, stmt->replace);
return viewOid;
}
/*
* Use the rules system to store the query for the view.
*/
voidStoreViewQuery(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);
}