pg-fix-inherit-rename-type-review.patch

diff --git a/src/backend/catalog/pg_inherits.c b/src/backend/catalog/pg_inherits.c
index e256f6f..fbde33a 100644
--- a/src/backend/catalog/pg_inherits.c
+++ b/src/backend/catalog/pg_inherits.c
@@ -28,6 +28,7 @@
 #include "parser/parse_type.h"
 #include "storage/lmgr.h"
 #include "utils/fmgroids.h"
+#include "utils/lsyscache.h"
 #include "utils/syscache.h"
 #include "utils/tqual.h"
 
@@ -190,6 +191,67 @@ find_all_inheritors(Oid parentrelId, LOCKMODE lockmode)
 	return rels_list;
 }
 
+/*
+ * find_column_origin
+ *
+ * Returns a list of relation OIDs the given column is inherited from.
+ * In most cases, a column has one origin, unless it (or its parent)
+ * has multiple ancestors.
+ * Note that find_column_origin() returns a unique OID for diamond-type 
+ * inheritance trees, because all relations shares the same origin.
+ */
+List *
+find_column_origin(Oid relOid, const char *colName)
+{
+	Relation	inhRel;
+	SysScanDesc	scan;
+	ScanKeyData	skey[1];
+	HeapTuple	tuple;
+	List	   *results = NIL;
+
+	/*
+	 * This relation does not contain the given column, so its
+	 * parent neither.
+	 */
+	if (get_attnum(relOid, colName) == InvalidAttrNumber)
+		return NIL;
+
+	inhRel = heap_open(InheritsRelationId, AccessShareLock);
+
+	ScanKeyInit(&skey[0],
+				Anum_pg_inherits_inhrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(relOid));
+
+	scan = systable_beginscan(inhRel, InheritsRelidSeqnoIndexId,
+							  true, SnapshotNow, 1, skey);
+
+	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
+	{
+		Form_pg_inherits	inhForm = (Form_pg_inherits) GETSTRUCT(tuple);
+		List	   *temp;
+
+		temp = find_column_origin(inhForm->inhparent, colName);
+		if (temp == NIL)
+			continue;
+
+		/*
+		 * Add to the queue only those children not already seen. This avoids
+		 * making duplicate entries in case of multiple inheritance paths from
+		 * the same parent.  (It'll also keep us from getting into an infinite
+		 * loop, though theoretically there can't be any cycles in the
+		 * inheritance graph anyway.)
+		 */
+		results = list_concat_unique_oid(results, temp);
+	}
+	systable_endscan(scan);
+	heap_close(inhRel, AccessShareLock);
+
+	if (results == NIL)
+		results = list_make1_oid(relOid);
+
+	return results;
+}
 
 /*
  * has_subclass - does this relation have any children?
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 10f0a94..4cd988c 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -2009,6 +2009,17 @@ renameatt(Oid myrelid,
 				 errmsg("cannot rename inherited column \"%s\"",
 						oldattname)));
 
+	/*
+	 * if the attribute is inherited multiple times, forbid the renaming,
+	 * even if we are already inside a recursive rename, because we
+	 * have no reasonable way to keep its integrity.
+	 */
+	if (list_length(find_column_origin(myrelid, oldattname)) > 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+				 (errmsg("cannot rename multiple inherited column \"%s\"",
+						 oldattname))));
+
 	/* new name should not already exist */
 
 	/* this test is deliberately not attisdropped-aware */
@@ -5768,6 +5779,7 @@ ATPrepAlterColumnType(List **wqueue,
 					  bool recurse, bool recursing,
 					  AlterTableCmd *cmd)
 {
+	Oid			relOid = RelationGetRelid(rel);
 	char	   *colName = cmd->name;
 	TypeName   *typeName = (TypeName *) cmd->def;
 	HeapTuple	tuple;
@@ -5803,6 +5815,13 @@ ATPrepAlterColumnType(List **wqueue,
 				 errmsg("cannot alter inherited column \"%s\"",
 						colName)));
 
+	/* Don't alter multiple inherited columns */
+	if (list_length(find_column_origin(relOid, colName)) > 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+				 (errmsg("cannot alter multiple inherited column \"%s\"",
+						 colName))));
+
 	/* Look up the target type */
 	targettype = typenameTypeId(NULL, typeName, &targettypmod);
 
diff --git a/src/include/catalog/pg_inherits_fn.h b/src/include/catalog/pg_inherits_fn.h
index 91baec3..a23f62b 100644
--- a/src/include/catalog/pg_inherits_fn.h
+++ b/src/include/catalog/pg_inherits_fn.h
@@ -19,6 +19,7 @@
 
 extern List *find_inheritance_children(Oid parentrelId, LOCKMODE lockmode);
 extern List *find_all_inheritors(Oid parentrelId, LOCKMODE lockmode);
+extern List *find_column_origin(Oid relOid, const char *colName);
 extern bool has_subclass(Oid relationId);
 extern bool typeInheritsFrom(Oid subclassTypeId, Oid superclassTypeId);
 
diff --git a/src/test/regress/expected/inherit.out b/src/test/regress/expected/inherit.out
index 9c83a32..3a049cc 100644
--- a/src/test/regress/expected/inherit.out
+++ b/src/test/regress/expected/inherit.out
@@ -1053,3 +1053,81 @@ NOTICE:  merging column "a" with inherited definition
 ERROR:  column "a" has a storage parameter conflict
 DETAIL:  MAIN versus EXTENDED
 DROP TABLE t1, t2, t3, t4, t12_storage, t12_comments, t1_inh, t13_inh, t13_like, t_all;
+-- Test for renaming and type changes (simple multiple inheritance)
+CREATE TABLE t1 (a int, b int);
+CREATE TABLE s1 (b int, c int);
+CREATE TABLE ts (d int) INHERITS (t1, s1);
+NOTICE:  merging multiple inherited definitions of column "b"
+ALTER TABLE s1 ALTER b TYPE float;	-- to be failed
+ERROR:  cannot alter multiple inherited column "b"
+ALTER TABLE s1 ALTER c TYPE float;
+ALTER TABLE ts ALTER c TYPE text;	-- to be failed
+ERROR:  cannot alter inherited column "c"
+ALTER TABLE ts ALTER d TYPE text;
+ALTER TABLE t1 RENAME a TO aa;
+ALTER TABLE t1 RENAME b TO bb;		-- to be failed
+ERROR:  cannot rename multiple inherited column "b"
+ALTER TABLE ts RENAME aa TO aaa;	-- to be failed
+ERROR:  cannot rename inherited column "aa"
+ALTER TABLE ts RENAME d TO dd;
+\d+ ts
+                       Table "public.ts"
+ Column |       Type       | Modifiers | Storage  | Description 
+--------+------------------+-----------+----------+-------------
+ aa     | integer          |           | plain    | 
+ b      | integer          |           | plain    | 
+ c      | double precision |           | plain    | 
+ dd     | text             |           | extended | 
+Inherits: t1,
+          s1
+Has OIDs: no
+
+DROP TABLE ts;
+-- Test for renaming and type changes (diamond inheritance)
+CREATE TABLE t2 (x int) INHERITS (t1);
+CREATE TABLE t3 (y int) INHERITS (t1);
+CREATE TABLE t4 (z int) INHERITS (t2, t3);
+NOTICE:  merging multiple inherited definitions of column "aa"
+NOTICE:  merging multiple inherited definitions of column "b"
+ALTER TABLE t1 ALTER aa TYPE float;
+ALTER TABLE t1 RENAME aa TO aaa;
+\d+ t4
+                       Table "public.t4"
+ Column |       Type       | Modifiers | Storage | Description 
+--------+------------------+-----------+---------+-------------
+ aaa    | double precision |           | plain   | 
+ b      | integer          |           | plain   | 
+ x      | integer          |           | plain   | 
+ y      | integer          |           | plain   | 
+ z      | integer          |           | plain   | 
+Inherits: t2,
+          t3
+Has OIDs: no
+
+CREATE TABLE ts (d int) INHERITS (t2, s1);
+NOTICE:  merging multiple inherited definitions of column "b"
+ALTER TABLE t1 ALTER aaa TYPE text;
+ALTER TABLE t1 ALTER b TYPE text;	-- to be failed
+ERROR:  cannot alter multiple inherited column "b"
+ALTER TABLE t1 RENAME aaa TO aaaa;
+ALTER TABLE t1 RENAME b TO bb;		-- to be failed
+ERROR:  cannot rename multiple inherited column "b"
+\d+ ts
+                       Table "public.ts"
+ Column |       Type       | Modifiers | Storage  | Description 
+--------+------------------+-----------+----------+-------------
+ aaaa   | text             |           | extended | 
+ b      | integer          |           | plain    | 
+ x      | integer          |           | plain    | 
+ c      | double precision |           | plain    | 
+ d      | integer          |           | plain    | 
+Inherits: t2,
+          s1
+Has OIDs: no
+
+DROP TABLE t1, s1 CASCADE;
+NOTICE:  drop cascades to 4 other objects
+DETAIL:  drop cascades to table t2
+drop cascades to table ts
+drop cascades to table t3
+drop cascades to table t4
diff --git a/src/test/regress/sql/inherit.sql b/src/test/regress/sql/inherit.sql
index 192e860..82ee7d3 100644
--- a/src/test/regress/sql/inherit.sql
+++ b/src/test/regress/sql/inherit.sql
@@ -334,3 +334,39 @@ CREATE TABLE inh_error1 () INHERITS (t1, t4);
 CREATE TABLE inh_error2 (LIKE t4 INCLUDING STORAGE) INHERITS (t1);
 
 DROP TABLE t1, t2, t3, t4, t12_storage, t12_comments, t1_inh, t13_inh, t13_like, t_all;
+
+-- Test for renaming and type changes (simple multiple inheritance)
+CREATE TABLE t1 (a int, b int);
+CREATE TABLE s1 (b int, c int);
+CREATE TABLE ts (d int) INHERITS (t1, s1);
+
+ALTER TABLE s1 ALTER b TYPE float;	-- to be failed
+ALTER TABLE s1 ALTER c TYPE float;
+ALTER TABLE ts ALTER c TYPE text;	-- to be failed
+ALTER TABLE ts ALTER d TYPE text;
+
+ALTER TABLE t1 RENAME a TO aa;
+ALTER TABLE t1 RENAME b TO bb;		-- to be failed
+ALTER TABLE ts RENAME aa TO aaa;	-- to be failed
+ALTER TABLE ts RENAME d TO dd;
+\d+ ts
+
+DROP TABLE ts;
+
+-- Test for renaming and type changes (diamond inheritance)
+CREATE TABLE t2 (x int) INHERITS (t1);
+CREATE TABLE t3 (y int) INHERITS (t1);
+CREATE TABLE t4 (z int) INHERITS (t2, t3);
+
+ALTER TABLE t1 ALTER aa TYPE float;
+ALTER TABLE t1 RENAME aa TO aaa;
+\d+ t4
+
+CREATE TABLE ts (d int) INHERITS (t2, s1);
+ALTER TABLE t1 ALTER aaa TYPE text;
+ALTER TABLE t1 ALTER b TYPE text;	-- to be failed
+ALTER TABLE t1 RENAME aaa TO aaaa;
+ALTER TABLE t1 RENAME b TO bb;		-- to be failed
+\d+ ts
+
+DROP TABLE t1, s1 CASCADE;