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view.c
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1 /*-------------------------------------------------------------------------
2  *
3  * view.c
4  * use rewrite rules to construct views
5  *
6  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
7  * Portions Copyright (c) 1994, Regents of the University of California
8  *
9  *
10  * IDENTIFICATION
11  * src/backend/commands/view.c
12  *
13  *-------------------------------------------------------------------------
14  */
15 #include "postgres.h"
16 
17 #include "access/relation.h"
18 #include "access/xact.h"
19 #include "catalog/namespace.h"
20 #include "commands/tablecmds.h"
21 #include "commands/view.h"
22 #include "nodes/makefuncs.h"
23 #include "nodes/nodeFuncs.h"
24 #include "parser/analyze.h"
25 #include "parser/parse_relation.h"
26 #include "rewrite/rewriteDefine.h"
27 #include "rewrite/rewriteHandler.h"
28 #include "rewrite/rewriteSupport.h"
29 #include "utils/builtins.h"
30 #include "utils/lsyscache.h"
31 #include "utils/rel.h"
32 
33 static void checkViewColumns(TupleDesc newdesc, TupleDesc olddesc);
34 
35 /*---------------------------------------------------------------------
36  * DefineVirtualRelation
37  *
38  * Create a view relation and use the rules system to store the query
39  * for the view.
40  *
41  * EventTriggerAlterTableStart must have been called already.
42  *---------------------------------------------------------------------
43  */
44 static ObjectAddress
45 DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace,
46  List *options, Query *viewParse)
47 {
48  Oid viewOid;
49  LOCKMODE lockmode;
50  CreateStmt *createStmt = makeNode(CreateStmt);
51  List *attrList;
52  ListCell *t;
53 
54  /*
55  * create a list of ColumnDef nodes based on the names and types of the
56  * (non-junk) targetlist items from the view's SELECT list.
57  */
58  attrList = NIL;
59  foreach(t, tlist)
60  {
61  TargetEntry *tle = (TargetEntry *) lfirst(t);
62 
63  if (!tle->resjunk)
64  {
65  ColumnDef *def = makeColumnDef(tle->resname,
66  exprType((Node *) tle->expr),
67  exprTypmod((Node *) tle->expr),
68  exprCollation((Node *) tle->expr));
69 
70  /*
71  * It's possible that the column is of a collatable type but the
72  * collation could not be resolved, so double-check.
73  */
74  if (type_is_collatable(exprType((Node *) tle->expr)))
75  {
76  if (!OidIsValid(def->collOid))
77  ereport(ERROR,
78  (errcode(ERRCODE_INDETERMINATE_COLLATION),
79  errmsg("could not determine which collation to use for view column \"%s\"",
80  def->colname),
81  errhint("Use the COLLATE clause to set the collation explicitly.")));
82  }
83  else
84  Assert(!OidIsValid(def->collOid));
85 
86  attrList = lappend(attrList, def);
87  }
88  }
89 
90  /*
91  * Look up, check permissions on, and lock the creation namespace; also
92  * check for a preexisting view with the same name. This will also set
93  * relation->relpersistence to RELPERSISTENCE_TEMP if the selected
94  * namespace is temporary.
95  */
96  lockmode = replace ? AccessExclusiveLock : NoLock;
97  (void) RangeVarGetAndCheckCreationNamespace(relation, lockmode, &viewOid);
98 
99  if (OidIsValid(viewOid) && replace)
100  {
101  Relation rel;
103  List *atcmds = NIL;
104  AlterTableCmd *atcmd;
105  ObjectAddress address;
106 
107  /* Relation is already locked, but we must build a relcache entry. */
108  rel = relation_open(viewOid, NoLock);
109 
110  /* Make sure it *is* a view. */
111  if (rel->rd_rel->relkind != RELKIND_VIEW)
112  ereport(ERROR,
113  (errcode(ERRCODE_WRONG_OBJECT_TYPE),
114  errmsg("\"%s\" is not a view",
115  RelationGetRelationName(rel))));
116 
117  /* Also check it's not in use already */
118  CheckTableNotInUse(rel, "CREATE OR REPLACE VIEW");
119 
120  /*
121  * Due to the namespace visibility rules for temporary objects, we
122  * should only end up replacing a temporary view with another
123  * temporary view, and similarly for permanent views.
124  */
125  Assert(relation->relpersistence == rel->rd_rel->relpersistence);
126 
127  /*
128  * Create a tuple descriptor to compare against the existing view, and
129  * verify that the old column list is an initial prefix of the new
130  * column list.
131  */
132  descriptor = BuildDescForRelation(attrList);
134 
135  /*
136  * If new attributes have been added, we must add pg_attribute entries
137  * for them. It is convenient (although overkill) to use the ALTER
138  * TABLE ADD COLUMN infrastructure for this.
139  *
140  * Note that we must do this before updating the query for the view,
141  * since the rules system requires that the correct view columns be in
142  * place when defining the new rules.
143  *
144  * Also note that ALTER TABLE doesn't run parse transformation on
145  * AT_AddColumnToView commands. The ColumnDef we supply must be ready
146  * to execute as-is.
147  */
148  if (list_length(attrList) > rel->rd_att->natts)
149  {
150  ListCell *c;
151  int skip = rel->rd_att->natts;
152 
153  foreach(c, attrList)
154  {
155  if (skip > 0)
156  {
157  skip--;
158  continue;
159  }
160  atcmd = makeNode(AlterTableCmd);
161  atcmd->subtype = AT_AddColumnToView;
162  atcmd->def = (Node *) lfirst(c);
163  atcmds = lappend(atcmds, atcmd);
164  }
165 
166  /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
167  AlterTableInternal(viewOid, atcmds, true);
168 
169  /* Make the new view columns visible */
171  }
172 
173  /*
174  * Update the query for the view.
175  *
176  * Note that we must do this before updating the view options, because
177  * the new options may not be compatible with the old view query (for
178  * example if we attempt to add the WITH CHECK OPTION, we require that
179  * the new view be automatically updatable, but the old view may not
180  * have been).
181  */
182  StoreViewQuery(viewOid, viewParse, replace);
183 
184  /* Make the new view query visible */
186 
187  /*
188  * Update the view's options.
189  *
190  * The new options list replaces the existing options list, even if
191  * it's empty.
192  */
193  atcmd = makeNode(AlterTableCmd);
194  atcmd->subtype = AT_ReplaceRelOptions;
195  atcmd->def = (Node *) options;
196  atcmds = list_make1(atcmd);
197 
198  /* EventTriggerAlterTableStart called by ProcessUtilitySlow */
199  AlterTableInternal(viewOid, atcmds, true);
200 
201  /*
202  * There is very little to do here to update the view's dependencies.
203  * Most view-level dependency relationships, such as those on the
204  * owner, schema, and associated composite type, aren't changing.
205  * Because we don't allow changing type or collation of an existing
206  * view column, those dependencies of the existing columns don't
207  * change either, while the AT_AddColumnToView machinery took care of
208  * adding such dependencies for new view columns. The dependencies of
209  * the view's query could have changed arbitrarily, but that was dealt
210  * with inside StoreViewQuery. What remains is only to check that
211  * view replacement is allowed when we're creating an extension.
212  */
213  ObjectAddressSet(address, RelationRelationId, viewOid);
214 
215  recordDependencyOnCurrentExtension(&address, true);
216 
217  /*
218  * Seems okay, so return the OID of the pre-existing view.
219  */
220  relation_close(rel, NoLock); /* keep the lock! */
221 
222  return address;
223  }
224  else
225  {
226  ObjectAddress address;
227 
228  /*
229  * Set the parameters for keys/inheritance etc. All of these are
230  * uninteresting for views...
231  */
232  createStmt->relation = relation;
233  createStmt->tableElts = attrList;
234  createStmt->inhRelations = NIL;
235  createStmt->constraints = NIL;
236  createStmt->options = options;
237  createStmt->oncommit = ONCOMMIT_NOOP;
238  createStmt->tablespacename = NULL;
239  createStmt->if_not_exists = false;
240 
241  /*
242  * Create the relation (this will error out if there's an existing
243  * view, so we don't need more code to complain if "replace" is
244  * false).
245  */
246  address = DefineRelation(createStmt, RELKIND_VIEW, InvalidOid, NULL,
247  NULL);
248  Assert(address.objectId != InvalidOid);
249 
250  /* Make the new view relation visible */
252 
253  /* Store the query for the view */
254  StoreViewQuery(address.objectId, viewParse, replace);
255 
256  return address;
257  }
258 }
259 
260 /*
261  * Verify that the columns associated with proposed new view definition match
262  * the columns of the old view. This is similar to equalRowTypes(), with code
263  * added to generate specific complaints. Also, we allow the new view to have
264  * more columns than the old.
265  */
266 static void
268 {
269  int i;
270 
271  if (newdesc->natts < olddesc->natts)
272  ereport(ERROR,
273  (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
274  errmsg("cannot drop columns from view")));
275 
276  for (i = 0; i < olddesc->natts; i++)
277  {
278  Form_pg_attribute newattr = TupleDescAttr(newdesc, i);
279  Form_pg_attribute oldattr = TupleDescAttr(olddesc, i);
280 
281  /* XXX msg not right, but we don't support DROP COL on view anyway */
282  if (newattr->attisdropped != oldattr->attisdropped)
283  ereport(ERROR,
284  (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
285  errmsg("cannot drop columns from view")));
286 
287  if (strcmp(NameStr(newattr->attname), NameStr(oldattr->attname)) != 0)
288  ereport(ERROR,
289  (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
290  errmsg("cannot change name of view column \"%s\" to \"%s\"",
291  NameStr(oldattr->attname),
292  NameStr(newattr->attname)),
293  errhint("Use ALTER VIEW ... RENAME COLUMN ... to change name of view column instead.")));
294 
295  /*
296  * We cannot allow type, typmod, or collation to change, since these
297  * properties may be embedded in Vars of other views/rules referencing
298  * this one. Other column attributes can be ignored.
299  */
300  if (newattr->atttypid != oldattr->atttypid ||
301  newattr->atttypmod != oldattr->atttypmod)
302  ereport(ERROR,
303  (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
304  errmsg("cannot change data type of view column \"%s\" from %s to %s",
305  NameStr(oldattr->attname),
306  format_type_with_typemod(oldattr->atttypid,
307  oldattr->atttypmod),
308  format_type_with_typemod(newattr->atttypid,
309  newattr->atttypmod))));
310 
311  /*
312  * At this point, attcollations should be both valid or both invalid,
313  * so applying get_collation_name unconditionally should be fine.
314  */
315  if (newattr->attcollation != oldattr->attcollation)
316  ereport(ERROR,
317  (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
318  errmsg("cannot change collation of view column \"%s\" from \"%s\" to \"%s\"",
319  NameStr(oldattr->attname),
320  get_collation_name(oldattr->attcollation),
321  get_collation_name(newattr->attcollation))));
322  }
323 
324  /*
325  * We ignore the constraint fields. The new view desc can't have any
326  * constraints, and the only ones that could be on the old view are
327  * defaults, which we are happy to leave in place.
328  */
329 }
330 
331 static void
332 DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
333 {
334  /*
335  * Set up the ON SELECT rule. Since the query has already been through
336  * parse analysis, we use DefineQueryRewrite() directly.
337  */
339  viewOid,
340  NULL,
341  CMD_SELECT,
342  true,
343  replace,
344  list_make1(viewParse));
345 
346  /*
347  * Someday: automatic ON INSERT, etc
348  */
349 }
350 
351 /*
352  * DefineView
353  * Execute a CREATE VIEW command.
354  */
356 DefineView(ViewStmt *stmt, const char *queryString,
357  int stmt_location, int stmt_len)
358 {
359  RawStmt *rawstmt;
360  Query *viewParse;
361  RangeVar *view;
362  ListCell *cell;
363  bool check_option;
364  ObjectAddress address;
365 
366  /*
367  * Run parse analysis to convert the raw parse tree to a Query. Note this
368  * also acquires sufficient locks on the source table(s).
369  */
370  rawstmt = makeNode(RawStmt);
371  rawstmt->stmt = stmt->query;
372  rawstmt->stmt_location = stmt_location;
373  rawstmt->stmt_len = stmt_len;
374 
375  viewParse = parse_analyze_fixedparams(rawstmt, queryString, NULL, 0, NULL);
376 
377  /*
378  * The grammar should ensure that the result is a single SELECT Query.
379  * However, it doesn't forbid SELECT INTO, so we have to check for that.
380  */
381  if (!IsA(viewParse, Query))
382  elog(ERROR, "unexpected parse analysis result");
383  if (viewParse->utilityStmt != NULL &&
384  IsA(viewParse->utilityStmt, CreateTableAsStmt))
385  ereport(ERROR,
386  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
387  errmsg("views must not contain SELECT INTO")));
388  if (viewParse->commandType != CMD_SELECT)
389  elog(ERROR, "unexpected parse analysis result");
390 
391  /*
392  * Check for unsupported cases. These tests are redundant with ones in
393  * DefineQueryRewrite(), but that function will complain about a bogus ON
394  * SELECT rule, and we'd rather the message complain about a view.
395  */
396  if (viewParse->hasModifyingCTE)
397  ereport(ERROR,
398  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
399  errmsg("views must not contain data-modifying statements in WITH")));
400 
401  /*
402  * If the user specified the WITH CHECK OPTION, add it to the list of
403  * reloptions.
404  */
405  if (stmt->withCheckOption == LOCAL_CHECK_OPTION)
406  stmt->options = lappend(stmt->options,
407  makeDefElem("check_option",
408  (Node *) makeString("local"), -1));
409  else if (stmt->withCheckOption == CASCADED_CHECK_OPTION)
410  stmt->options = lappend(stmt->options,
411  makeDefElem("check_option",
412  (Node *) makeString("cascaded"), -1));
413 
414  /*
415  * Check that the view is auto-updatable if WITH CHECK OPTION was
416  * specified.
417  */
418  check_option = false;
419 
420  foreach(cell, stmt->options)
421  {
422  DefElem *defel = (DefElem *) lfirst(cell);
423 
424  if (strcmp(defel->defname, "check_option") == 0)
425  check_option = true;
426  }
427 
428  /*
429  * If the check option is specified, look to see if the view is actually
430  * auto-updatable or not.
431  */
432  if (check_option)
433  {
434  const char *view_updatable_error =
435  view_query_is_auto_updatable(viewParse, true);
436 
437  if (view_updatable_error)
438  ereport(ERROR,
439  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
440  errmsg("WITH CHECK OPTION is supported only on automatically updatable views"),
441  errhint("%s", _(view_updatable_error))));
442  }
443 
444  /*
445  * If a list of column names was given, run through and insert these into
446  * the actual query tree. - thomas 2000-03-08
447  */
448  if (stmt->aliases != NIL)
449  {
450  ListCell *alist_item = list_head(stmt->aliases);
451  ListCell *targetList;
452 
453  foreach(targetList, viewParse->targetList)
454  {
455  TargetEntry *te = lfirst_node(TargetEntry, targetList);
456 
457  /* junk columns don't get aliases */
458  if (te->resjunk)
459  continue;
460  te->resname = pstrdup(strVal(lfirst(alist_item)));
461  alist_item = lnext(stmt->aliases, alist_item);
462  if (alist_item == NULL)
463  break; /* done assigning aliases */
464  }
465 
466  if (alist_item != NULL)
467  ereport(ERROR,
468  (errcode(ERRCODE_SYNTAX_ERROR),
469  errmsg("CREATE VIEW specifies more column "
470  "names than columns")));
471  }
472 
473  /* Unlogged views are not sensible. */
474  if (stmt->view->relpersistence == RELPERSISTENCE_UNLOGGED)
475  ereport(ERROR,
476  (errcode(ERRCODE_SYNTAX_ERROR),
477  errmsg("views cannot be unlogged because they do not have storage")));
478 
479  /*
480  * If the user didn't explicitly ask for a temporary view, check whether
481  * we need one implicitly. We allow TEMP to be inserted automatically as
482  * long as the CREATE command is consistent with that --- no explicit
483  * schema name.
484  */
485  view = copyObject(stmt->view); /* don't corrupt original command */
486  if (view->relpersistence == RELPERSISTENCE_PERMANENT
487  && isQueryUsingTempRelation(viewParse))
488  {
489  view->relpersistence = RELPERSISTENCE_TEMP;
490  ereport(NOTICE,
491  (errmsg("view \"%s\" will be a temporary view",
492  view->relname)));
493  }
494 
495  /*
496  * Create the view relation
497  *
498  * NOTE: if it already exists and replace is false, the xact will be
499  * aborted.
500  */
501  address = DefineVirtualRelation(view, viewParse->targetList,
502  stmt->replace, stmt->options, viewParse);
503 
504  return address;
505 }
506 
507 /*
508  * Use the rules system to store the query for the view.
509  */
510 void
511 StoreViewQuery(Oid viewOid, Query *viewParse, bool replace)
512 {
513  /*
514  * Now create the rules associated with the view.
515  */
516  DefineViewRules(viewOid, viewParse, replace);
517 }
#define NameStr(name)
Definition: c.h:746
#define Assert(condition)
Definition: c.h:858
#define OidIsValid(objectId)
Definition: c.h:775
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Definition: elog.c:1319
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Definition: elog.c:859
int errmsg(const char *fmt,...)
Definition: elog.c:1072
#define _(x)
Definition: elog.c:90
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Definition: elog.h:39
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Definition: elog.h:224
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Definition: elog.h:35
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int32 exprTypmod(const Node *expr)
Definition: nodeFuncs.c:298
Oid exprCollation(const Node *expr)
Definition: nodeFuncs.c:816
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#define copyObject(obj)
Definition: nodes.h:224
@ CMD_SELECT
Definition: nodes.h:265
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Definition: nodes.h:155
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Definition: objectaddress.h:40
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@ AT_ReplaceRelOptions
Definition: parsenodes.h:2390
@ AT_AddColumnToView
Definition: parsenodes.h:2354
@ CASCADED_CHECK_OPTION
Definition: parsenodes.h:3747
@ LOCAL_CHECK_OPTION
Definition: parsenodes.h:3746
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FormData_pg_attribute * Form_pg_attribute
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Definition: pg_list.h:176
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#define NIL
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#define InvalidOid
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unsigned int Oid
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char * c
@ ONCOMMIT_NOOP
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#define RelationGetRelationName(relation)
Definition: rel.h:539
ObjectAddress DefineQueryRewrite(const char *rulename, Oid event_relid, Node *event_qual, CmdType event_type, bool is_instead, bool replace, List *action)
const char * view_query_is_auto_updatable(Query *viewquery, bool check_cols)
#define ViewSelectRuleName
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Relation relation_open(Oid relationId, LOCKMODE lockmode)
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AlterTableType subtype
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Oid collOid
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List * options
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List * inhRelations
Definition: parsenodes.h:2658
RangeVar * relation
Definition: parsenodes.h:2656
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char * defname
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ParseLoc stmt_location
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ParseLoc stmt_len
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Node * stmt
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Form_pg_class rd_rel
Definition: rel.h:111
Expr * expr
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Definition: tablecmds.c:4345
ObjectAddress DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId, ObjectAddress *typaddress, const char *queryString)
Definition: tablecmds.c:699
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Definition: tablecmds.c:4461
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Definition: tupdesc.h:92
String * makeString(char *str)
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#define strVal(v)
Definition: value.h:82
static ObjectAddress DefineVirtualRelation(RangeVar *relation, List *tlist, bool replace, List *options, Query *viewParse)
Definition: view.c:45
static void checkViewColumns(TupleDesc newdesc, TupleDesc olddesc)
Definition: view.c:267
static void DefineViewRules(Oid viewOid, Query *viewParse, bool replace)
Definition: view.c:332
ObjectAddress DefineView(ViewStmt *stmt, const char *queryString, int stmt_location, int stmt_len)
Definition: view.c:356
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Definition: view.c:511
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