Fix ALTER TABLE / SET TYPE for irregular inheritance

If inherited tables don't have exactly the same schema, the USING clause
in an ALTER TABLE / SET DATA TYPE misbehaves when applied to the
children tables since commit 9550e83.  Starting with that commit,
the attribute numbers in the USING expression are fixed during parse
analysis.  This can lead to bogus errors being reported during
execution, such as:
   ERROR:  attribute 2 has wrong type
   DETAIL:  Table has type smallint, but query expects integer.

Since it wouldn't do to revert to the original coding, we now apply a
transformation to map the attribute numbers to the correct ones for each
child.

Reported by Justin Pryzby
Analysis by Tom Lane; patch by me.
Discussion: https://postgr.es/m/20170102225618.GA10071@telsasoft.com

Author: alvherre

src/backend/access/common/tupconvert.c

@@ -206,55 +206,12 @@ convert_tuples_by_name(TupleDesc indesc,
 {
 	TupleConversionMap *map;
 	AttrNumber *attrMap;
-	int			n;
+	int			n = outdesc->natts;
 	int			i;
 	bool		same;
 
 	/* Verify compatibility and prepare attribute-number map */
-	n = outdesc->natts;
-	attrMap = (AttrNumber *) palloc0(n * sizeof(AttrNumber));
-	for (i = 0; i < n; i++)
-	{
-		Form_pg_attribute att = outdesc->attrs[i];
-		char	   *attname;
-		Oid			atttypid;
-		int32		atttypmod;
-		int			j;
-
-		if (att->attisdropped)
-			continue;			/* attrMap[i] is already 0 */
-		attname = NameStr(att->attname);
-		atttypid = att->atttypid;
-		atttypmod = att->atttypmod;
-		for (j = 0; j < indesc->natts; j++)
-		{
-			att = indesc->attrs[j];
-			if (att->attisdropped)
-				continue;
-			if (strcmp(attname, NameStr(att->attname)) == 0)
-			{
-				/* Found it, check type */
-				if (atttypid != att->atttypid || atttypmod != att->atttypmod)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATATYPE_MISMATCH),
-							 errmsg_internal("%s", _(msg)),
-							 errdetail("Attribute \"%s\" of type %s does not match corresponding attribute of type %s.",
-									   attname,
-									   format_type_be(outdesc->tdtypeid),
-									   format_type_be(indesc->tdtypeid))));
-				attrMap[i] = (AttrNumber) (j + 1);
-				break;
-			}
-		}
-		if (attrMap[i] == 0)
-			ereport(ERROR,
-					(errcode(ERRCODE_DATATYPE_MISMATCH),
-					 errmsg_internal("%s", _(msg)),
-					 errdetail("Attribute \"%s\" of type %s does not exist in type %s.",
-							   attname,
-							   format_type_be(outdesc->tdtypeid),
-							   format_type_be(indesc->tdtypeid))));
-	}
+	attrMap = convert_tuples_by_name_map(indesc, outdesc, msg);
 
 	/*
 	 * Check to see if the map is one-to-one and the tuple types are the same.
@@ -312,6 +269,69 @@ convert_tuples_by_name(TupleDesc indesc,
 	return map;
 }
 
+/*
+ * Return a palloc'd bare attribute map for tuple conversion, matching input
+ * and output columns by name.  (Dropped columns are ignored in both input and
+ * output.)  This is normally a subroutine for convert_tuples_by_name, but can
+ * be used standalone.
+ */
+AttrNumber *
+convert_tuples_by_name_map(TupleDesc indesc,
+						   TupleDesc outdesc,
+						   const char *msg)
+{
+	AttrNumber *attrMap;
+	int			n;
+	int			i;
+
+	n = outdesc->natts;
+	attrMap = (AttrNumber *) palloc0(n * sizeof(AttrNumber));
+	for (i = 0; i < n; i++)
+	{
+		Form_pg_attribute att = outdesc->attrs[i];
+		char	   *attname;
+		Oid			atttypid;
+		int32		atttypmod;
+		int			j;
+
+		if (att->attisdropped)
+			continue;			/* attrMap[i] is already 0 */
+		attname = NameStr(att->attname);
+		atttypid = att->atttypid;
+		atttypmod = att->atttypmod;
+		for (j = 0; j < indesc->natts; j++)
+		{
+			att = indesc->attrs[j];
+			if (att->attisdropped)
+				continue;
+			if (strcmp(attname, NameStr(att->attname)) == 0)
+			{
+				/* Found it, check type */
+				if (atttypid != att->atttypid || atttypmod != att->atttypmod)
+					ereport(ERROR,
+							(errcode(ERRCODE_DATATYPE_MISMATCH),
+							 errmsg_internal("%s", _(msg)),
+							 errdetail("Attribute \"%s\" of type %s does not match corresponding attribute of type %s.",
+									   attname,
+									   format_type_be(outdesc->tdtypeid),
+									   format_type_be(indesc->tdtypeid))));
+				attrMap[i] = (AttrNumber) (j + 1);
+				break;
+			}
+		}
+		if (attrMap[i] == 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg_internal("%s", _(msg)),
+					 errdetail("Attribute \"%s\" of type %s does not exist in type %s.",
+							   attname,
+							   format_type_be(outdesc->tdtypeid),
+							   format_type_be(indesc->tdtypeid))));
+	}
+
+	return attrMap;
+}
+
 /*
  * Perform conversion of a tuple according to the map.
  */

src/backend/commands/tablecmds.c

@@ -20,6 +20,7 @@
 #include "access/reloptions.h"
 #include "access/relscan.h"
 #include "access/sysattr.h"
+#include "access/tupconvert.h"
 #include "access/xact.h"
 #include "access/xlog.h"
 #include "catalog/catalog.h"
@@ -8540,12 +8541,69 @@ ATPrepAlterColumnType(List **wqueue,
 	ReleaseSysCache(tuple);
 
 	/*
-	 * The recursion case is handled by ATSimpleRecursion.  However, if we are
-	 * told not to recurse, there had better not be any child tables; else the
-	 * alter would put them out of step.
+	 * Recurse manually by queueing a new command for each child, if
+	 * necessary. We cannot apply ATSimpleRecursion here because we need to
+	 * remap attribute numbers in the USING expression, if any.
+	 *
+	 * If we are told not to recurse, there had better not be any child
+	 * tables; else the alter would put them out of step.
 	 */
 	if (recurse)
-		ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
+	{
+		Oid			relid = RelationGetRelid(rel);
+		ListCell   *child;
+		List	   *children;
+
+		children = find_all_inheritors(relid, lockmode, NULL);
+
+		/*
+		 * find_all_inheritors does the recursive search of the inheritance
+		 * hierarchy, so all we have to do is process all of the relids in the
+		 * list that it returns.
+		 */
+		foreach(child, children)
+		{
+			Oid			childrelid = lfirst_oid(child);
+			Relation	childrel;
+
+			if (childrelid == relid)
+				continue;
+
+			/* find_all_inheritors already got lock */
+			childrel = relation_open(childrelid, NoLock);
+			CheckTableNotInUse(childrel, "ALTER TABLE");
+
+			/*
+			 * Remap the attribute numbers.  If no USING expression was
+			 * specified, there is no need for this step.
+			 */
+			if (def->cooked_default)
+			{
+				AttrNumber *attmap;
+				bool		found_whole_row;
+
+				/* create a copy to scribble on */
+				cmd = copyObject(cmd);
+
+				attmap = convert_tuples_by_name_map(RelationGetDescr(childrel),
+													RelationGetDescr(rel),
+								 gettext_noop("could not convert row type"));
+				((ColumnDef *) cmd->def)->cooked_default =
+					map_variable_attnos(def->cooked_default,
+										1, 0,
+										attmap, RelationGetDescr(rel)->natts,
+										&found_whole_row);
+				if (found_whole_row)
+					ereport(ERROR,
+							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						  errmsg("cannot convert whole-row table reference"),
+							 errdetail("USING expression contains a whole-row table reference.")));
+				pfree(attmap);
+			}
+			ATPrepCmd(wqueue, childrel, cmd, false, true, lockmode);
+			relation_close(childrel, NoLock);
+		}
+	}
 	else if (!recursing &&
 			 find_inheritance_children(RelationGetRelid(rel), NoLock) != NIL)
 		ereport(ERROR,

src/include/access/tupconvert.h

@@ -38,6 +38,10 @@ extern TupleConversionMap *convert_tuples_by_name(TupleDesc indesc,
 					   TupleDesc outdesc,
 					   const char *msg);
 
+extern AttrNumber *convert_tuples_by_name_map(TupleDesc indesc,
+						   TupleDesc outdesc,
+						   const char *msg);
+
 extern HeapTuple do_convert_tuple(HeapTuple tuple, TupleConversionMap *map);
 
 extern void free_conversion_map(TupleConversionMap *map);

src/test/regress/expected/alter_table.out

@@ -2048,6 +2048,28 @@ select relname, conname, coninhcount, conislocal, connoinherit
  test_inh_check_child | test_inh_check_a_check |           1 | f          | f
 (6 rows)
 
+-- ALTER COLUMN TYPE with different schema in children
+-- Bug at https://postgr.es/m/20170102225618.GA10071@telsasoft.com
+CREATE TABLE test_type_diff (f1 int);
+CREATE TABLE test_type_diff_c (extra smallint) INHERITS (test_type_diff);
+ALTER TABLE test_type_diff ADD COLUMN f2 int;
+INSERT INTO test_type_diff_c VALUES (1, 2, 3);
+ALTER TABLE test_type_diff ALTER COLUMN f2 TYPE bigint USING f2::bigint;
+CREATE TABLE test_type_diff2 (int_two int2, int_four int4, int_eight int8);
+CREATE TABLE test_type_diff2_c1 (int_four int4, int_eight int8, int_two int2);
+CREATE TABLE test_type_diff2_c2 (int_eight int8, int_two int2, int_four int4);
+CREATE TABLE test_type_diff2_c3 (int_two int2, int_four int4, int_eight int8);
+ALTER TABLE test_type_diff2_c1 INHERIT test_type_diff2;
+ALTER TABLE test_type_diff2_c2 INHERIT test_type_diff2;
+ALTER TABLE test_type_diff2_c3 INHERIT test_type_diff2;
+INSERT INTO test_type_diff2_c1 VALUES (1, 2, 3);
+INSERT INTO test_type_diff2_c2 VALUES (4, 5, 6);
+INSERT INTO test_type_diff2_c3 VALUES (7, 8, 9);
+ALTER TABLE test_type_diff2 ALTER COLUMN int_four TYPE int8 USING int_four::int8;
+-- whole-row references are disallowed
+ALTER TABLE test_type_diff2 ALTER COLUMN int_four TYPE int4 USING (pg_column_size(test_type_diff2));
+ERROR:  cannot convert whole-row table reference
+DETAIL:  USING expression contains a whole-row table reference.
 -- check for rollback of ANALYZE corrupting table property flags (bug #11638)
 CREATE TABLE check_fk_presence_1 (id int PRIMARY KEY, t text);
 CREATE TABLE check_fk_presence_2 (id int REFERENCES check_fk_presence_1, t text);

src/test/regress/sql/alter_table.sql

@@ -1335,6 +1335,28 @@ select relname, conname, coninhcount, conislocal, connoinherit
   where relname like 'test_inh_check%' and c.conrelid = r.oid
   order by 1, 2;
 
+-- ALTER COLUMN TYPE with different schema in children
+-- Bug at https://postgr.es/m/20170102225618.GA10071@telsasoft.com
+CREATE TABLE test_type_diff (f1 int);
+CREATE TABLE test_type_diff_c (extra smallint) INHERITS (test_type_diff);
+ALTER TABLE test_type_diff ADD COLUMN f2 int;
+INSERT INTO test_type_diff_c VALUES (1, 2, 3);
+ALTER TABLE test_type_diff ALTER COLUMN f2 TYPE bigint USING f2::bigint;
+
+CREATE TABLE test_type_diff2 (int_two int2, int_four int4, int_eight int8);
+CREATE TABLE test_type_diff2_c1 (int_four int4, int_eight int8, int_two int2);
+CREATE TABLE test_type_diff2_c2 (int_eight int8, int_two int2, int_four int4);
+CREATE TABLE test_type_diff2_c3 (int_two int2, int_four int4, int_eight int8);
+ALTER TABLE test_type_diff2_c1 INHERIT test_type_diff2;
+ALTER TABLE test_type_diff2_c2 INHERIT test_type_diff2;
+ALTER TABLE test_type_diff2_c3 INHERIT test_type_diff2;
+INSERT INTO test_type_diff2_c1 VALUES (1, 2, 3);
+INSERT INTO test_type_diff2_c2 VALUES (4, 5, 6);
+INSERT INTO test_type_diff2_c3 VALUES (7, 8, 9);
+ALTER TABLE test_type_diff2 ALTER COLUMN int_four TYPE int8 USING int_four::int8;
+-- whole-row references are disallowed
+ALTER TABLE test_type_diff2 ALTER COLUMN int_four TYPE int4 USING (pg_column_size(test_type_diff2));
+
 -- check for rollback of ANALYZE corrupting table property flags (bug #11638)
 CREATE TABLE check_fk_presence_1 (id int PRIMARY KEY, t text);
 CREATE TABLE check_fk_presence_2 (id int REFERENCES check_fk_presence_1, t text);