Allow RECORD and RECORD[] to be specified in function coldeflists.

We can't allow these pseudo-types to be used as table column types,
because storing an anonymous record value in a table would result
in data that couldn't be understood by other sessions.  However,
it seems like there's no harm in allowing the case in a column
definition list that's specifying what a function-returning-record
returns.  The data involved is all local to the current session,
so we should be just as able to resolve its actual tuple type as
we are for the function-returning-record's top-level tuple output.

Elvis Pranskevichus, with cosmetic changes by me

Discussion: https://postgr.es/m/11038447.kQ5A9Uj5xi@hammer.magicstack.net

Author: tglsfdc

src/backend/catalog/heap.c

@@ -445,11 +445,14 @@ heap_create(const char *relname,
  *		this is used to make certain the tuple descriptor contains a
  *		valid set of attribute names and datatypes.  a problem simply
  *		generates ereport(ERROR) which aborts the current transaction.
+ *
+ *		relkind is the relkind of the relation to be created.
+ *		flags controls which datatypes are allowed, cf CheckAttributeType.
  * --------------------------------
  */
 void
 CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind,
-						 bool allow_system_table_mods)
+						 int flags)
 {
 	int			i;
 	int			j;
@@ -507,7 +510,7 @@ CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind,
 						   TupleDescAttr(tupdesc, i)->atttypid,
 						   TupleDescAttr(tupdesc, i)->attcollation,
 						   NIL, /* assume we're creating a new rowtype */
-						   allow_system_table_mods);
+						   flags);
 	}
 }
 
@@ -524,26 +527,41 @@ CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind,
  * containing_rowtypes.  When checking a to-be-created rowtype, it's
  * sufficient to pass NIL, because there could not be any recursive reference
  * to a not-yet-existing rowtype.
+ *
+ * flags is a bitmask controlling which datatypes we allow.  For the most
+ * part, pseudo-types are disallowed as attribute types, but there are some
+ * exceptions: ANYARRAYOID, RECORDOID, and RECORDARRAYOID can be allowed
+ * in some cases.  (This works because values of those type classes are
+ * self-identifying to some extent.  However, RECORDOID and RECORDARRAYOID
+ * are reliably identifiable only within a session, since the identity info
+ * may use a typmod that is only locally assigned.  The caller is expected
+ * to know whether these cases are safe.)
  * --------------------------------
  */
 void
 CheckAttributeType(const char *attname,
 				   Oid atttypid, Oid attcollation,
 				   List *containing_rowtypes,
-				   bool allow_system_table_mods)
+				   int flags)
 {
 	char		att_typtype = get_typtype(atttypid);
 	Oid			att_typelem;
 
 	if (att_typtype == TYPTYPE_PSEUDO)
 	{
 		/*
-		 * Refuse any attempt to create a pseudo-type column, except for a
-		 * special hack for pg_statistic: allow ANYARRAY when modifying system
-		 * catalogs (this allows creating pg_statistic and cloning it during
-		 * VACUUM FULL)
+		 * We disallow pseudo-type columns, with the exception of ANYARRAY,
+		 * RECORD, and RECORD[] when the caller says that those are OK.
+		 *
+		 * We don't need to worry about recursive containment for RECORD and
+		 * RECORD[] because (a) no named composite type should be allowed to
+		 * contain those, and (b) two "anonymous" record types couldn't be
+		 * considered to be the same type, so infinite recursion isn't
+		 * possible.
 		 */
-		if (atttypid != ANYARRAYOID || !allow_system_table_mods)
+		if (!((atttypid == ANYARRAYOID && (flags & CHKATYPE_ANYARRAY)) ||
+			  (atttypid == RECORDOID && (flags & CHKATYPE_ANYRECORD)) ||
+			  (atttypid == RECORDARRAYOID && (flags & CHKATYPE_ANYRECORD))))
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 					 errmsg("column \"%s\" has pseudo-type %s",
@@ -556,7 +574,7 @@ CheckAttributeType(const char *attname,
 		 */
 		CheckAttributeType(attname, getBaseType(atttypid), attcollation,
 						   containing_rowtypes,
-						   allow_system_table_mods);
+						   flags);
 	}
 	else if (att_typtype == TYPTYPE_COMPOSITE)
 	{
@@ -594,7 +612,7 @@ CheckAttributeType(const char *attname,
 			CheckAttributeType(NameStr(attr->attname),
 							   attr->atttypid, attr->attcollation,
 							   containing_rowtypes,
-							   allow_system_table_mods);
+							   flags);
 		}
 
 		relation_close(relation, AccessShareLock);
@@ -608,7 +626,7 @@ CheckAttributeType(const char *attname,
 		 */
 		CheckAttributeType(attname, att_typelem, attcollation,
 						   containing_rowtypes,
-						   allow_system_table_mods);
+						   flags);
 	}
 
 	/*
@@ -1074,7 +1092,13 @@ heap_create_with_catalog(const char *relname,
 	 */
 	Assert(IsNormalProcessingMode() || IsBootstrapProcessingMode());
 
-	CheckAttributeNamesTypes(tupdesc, relkind, allow_system_table_mods);
+	/*
+	 * Validate proposed tupdesc for the desired relkind.  If
+	 * allow_system_table_mods is on, allow ANYARRAY to be used; this is a
+	 * hack to allow creating pg_statistic and cloning it during VACUUM FULL.
+	 */
+	CheckAttributeNamesTypes(tupdesc, relkind,
+							 allow_system_table_mods ? CHKATYPE_ANYARRAY : 0);
 
 	/*
 	 * This would fail later on anyway, if the relation already exists.  But

src/backend/catalog/index.c

@@ -410,7 +410,7 @@ ConstructTupleDescriptor(Relation heapRelation,
 			 */
 			CheckAttributeType(NameStr(to->attname),
 							   to->atttypid, to->attcollation,
-							   NIL, false);
+							   NIL, 0);
 		}
 
 		/*

src/backend/commands/tablecmds.c

@@ -5505,7 +5505,7 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	/* make sure datatype is legal for a column */
 	CheckAttributeType(colDef->colname, typeOid, collOid,
 					   list_make1_oid(rel->rd_rel->reltype),
-					   false);
+					   0);
 
 	/* construct new attribute's pg_attribute entry */
 	attribute.attrelid = myrelid;
@@ -9445,7 +9445,7 @@ ATPrepAlterColumnType(List **wqueue,
 	/* make sure datatype is legal for a column */
 	CheckAttributeType(colName, targettype, targetcollid,
 					   list_make1_oid(rel->rd_rel->reltype),
-					   false);
+					   0);
 
 	if (tab->relkind == RELKIND_RELATION ||
 		tab->relkind == RELKIND_PARTITIONED_TABLE)

src/backend/parser/parse_relation.c

@@ -1590,9 +1590,15 @@ addRangeTableEntryForFunction(ParseState *pstate,
 
 			/*
 			 * Ensure that the coldeflist defines a legal set of names (no
-			 * duplicates) and datatypes (no pseudo-types, for instance).
+			 * duplicates, but we needn't worry about system column names) and
+			 * datatypes.  Although we mostly can't allow pseudo-types, it
+			 * seems safe to allow RECORD and RECORD[], since values within
+			 * those type classes are self-identifying at runtime, and the
+			 * coldeflist doesn't represent anything that will be visible to
+			 * other sessions.
 			 */
-			CheckAttributeNamesTypes(tupdesc, RELKIND_COMPOSITE_TYPE, false);
+			CheckAttributeNamesTypes(tupdesc, RELKIND_COMPOSITE_TYPE,
+									 CHKATYPE_ANYRECORD);
 		}
 		else
 			ereport(ERROR,

src/include/catalog/heap.h

@@ -19,6 +19,10 @@
 #include "parser/parse_node.h"
 
 
+/* flag bits for CheckAttributeType/CheckAttributeNamesTypes */
+#define CHKATYPE_ANYARRAY		0x01	/* allow ANYARRAY */
+#define CHKATYPE_ANYRECORD		0x02	/* allow RECORD and RECORD[] */
+
 typedef struct RawColumnDefault
 {
 	AttrNumber	attnum;			/* attribute to attach default to */
@@ -130,12 +134,12 @@ extern const FormData_pg_attribute *SystemAttributeDefinition(AttrNumber attno);
 extern const FormData_pg_attribute *SystemAttributeByName(const char *attname);
 
 extern void CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind,
-						 bool allow_system_table_mods);
+						 int flags);
 
 extern void CheckAttributeType(const char *attname,
 				   Oid atttypid, Oid attcollation,
 				   List *containing_rowtypes,
-				   bool allow_system_table_mods);
+				   int flags);
 
 /* pg_partitioned_table catalog manipulation functions */
 extern void StorePartitionKey(Relation rel,

src/test/regress/expected/rowtypes.out

@@ -667,6 +667,17 @@ select row(1, '(1,2)')::testtype6 *<> row(1, '(1,3)')::testtype6;
  t
 (1 row)
 
+-- anonymous rowtypes in coldeflists
+select q.a, q.b = row(2), q.c = array[row(3)], q.d = row(row(4)) from
+    unnest(array[row(1, row(2), array[row(3)], row(row(4))),
+                 row(2, row(3), array[row(4)], row(row(5)))])
+      as q(a int, b record, c record[], d record);
+ a | ?column? | ?column? | ?column? 
+---+----------+----------+----------
+ 1 | t        | t        | t
+ 2 | f        | f        | f
+(2 rows)
+
 drop type testtype1, testtype2, testtype3, testtype4, testtype5, testtype6;
 --
 -- Test case derived from bug #5716: check multiple uses of a rowtype result

src/test/regress/sql/rowtypes.sql

@@ -259,6 +259,12 @@ select row(1, '(1,2)')::testtype6 *< row(1, '(1,3)')::testtype6;
 select row(1, '(1,2)')::testtype6 *>= row(1, '(1,3)')::testtype6;
 select row(1, '(1,2)')::testtype6 *<> row(1, '(1,3)')::testtype6;
 
+-- anonymous rowtypes in coldeflists
+select q.a, q.b = row(2), q.c = array[row(3)], q.d = row(row(4)) from
+    unnest(array[row(1, row(2), array[row(3)], row(row(4))),
+                 row(2, row(3), array[row(4)], row(row(5)))])
+      as q(a int, b record, c record[], d record);
+
 drop type testtype1, testtype2, testtype3, testtype4, testtype5, testtype6;