diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 63cc3e3f40..9602fc5461 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -1001,6 +1001,19 @@ DefineIndex(Oid relationId,
 					bool		found_whole_row;
 					ListCell   *lc;
 
+					/*
+					 * We can't use the same index name for the child index,
+					 * so clear idxname to let the recursive invocation choose
+					 * a new name.  Likewise, the existing target relation
+					 * field is wrong, and if indexOid or oldNode are set,
+					 * they mustn't be applied to the child either.
+					 */
+					childStmt->idxname = NULL;
+					childStmt->relation = NULL;
+					childStmt->relationId = childRelid;
+					childStmt->indexOid = InvalidOid;
+					childStmt->oldNode = InvalidOid;
+
 					/*
 					 * Adjust any Vars (both in expressions and in the index's
 					 * WHERE clause) to match the partition's column numbering
@@ -1032,8 +1045,6 @@ DefineIndex(Oid relationId,
 					if (found_whole_row)
 						elog(ERROR, "cannot convert whole-row table reference");
 
-					childStmt->idxname = NULL;
-					childStmt->relationId = childRelid;
 					DefineIndex(childRelid, childStmt,
 								InvalidOid, /* no predefined OID */
 								indexRelationId,	/* this is our child */
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index cf61cc1ac4..6bba661724 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -10694,7 +10694,9 @@ TryReuseIndex(Oid oldId, IndexStmt *stmt)
 	{
 		Relation	irel = index_open(oldId, NoLock);
 
-		stmt->oldNode = irel->rd_node.relNode;
+		/* If it's a partitioned index, there is no storage to share. */
+		if (irel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
+			stmt->oldNode = irel->rd_node.relNode;
 		index_close(irel, NoLock);
 	}
 }
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index b9aa4f189b..c3a650d4f2 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -2081,6 +2081,94 @@ Indexes:
     "at_part_2_a_idx" btree (a)
     "at_part_2_b_idx" btree (b)
 
+drop table at_partitioned;
+-- Alter column type when no table rewrite is required
+-- Also check that comments are preserved
+create table at_partitioned(id int, name varchar(64), unique (id, name))
+  partition by hash(id);
+comment on constraint at_partitioned_id_name_key on at_partitioned is 'parent constraint';
+comment on index at_partitioned_id_name_key is 'parent index';
+create table at_partitioned_0 partition of at_partitioned
+  for values with (modulus 2, remainder 0);
+comment on constraint at_partitioned_0_id_name_key on at_partitioned_0 is 'child 0 constraint';
+comment on index at_partitioned_0_id_name_key is 'child 0 index';
+create table at_partitioned_1 partition of at_partitioned
+  for values with (modulus 2, remainder 1);
+comment on constraint at_partitioned_1_id_name_key on at_partitioned_1 is 'child 1 constraint';
+comment on index at_partitioned_1_id_name_key is 'child 1 index';
+insert into at_partitioned values(1, 'foo');
+insert into at_partitioned values(3, 'bar');
+create temp table old_oids as
+  select relname, oid as oldoid, relfilenode as oldfilenode
+  from pg_class where relname like 'at_partitioned%';
+select relname,
+  c.oid = oldoid as orig_oid,
+  case relfilenode
+    when 0 then 'none'
+    when c.oid then 'own'
+    when oldfilenode then 'orig'
+    else 'OTHER'
+    end as storage,
+  obj_description(c.oid, 'pg_class') as desc
+  from pg_class c left join old_oids using (relname)
+  where relname like 'at_partitioned%'
+  order by relname;
+           relname            | orig_oid | storage |     desc      
+------------------------------+----------+---------+---------------
+ at_partitioned               | t        | own     | 
+ at_partitioned_0             | t        | own     | 
+ at_partitioned_0_id_name_key | t        | own     | child 0 index
+ at_partitioned_1             | t        | own     | 
+ at_partitioned_1_id_name_key | t        | own     | child 1 index
+ at_partitioned_id_name_key   | t        | own     | parent index
+(6 rows)
+
+select conname, obj_description(oid, 'pg_constraint') as desc
+  from pg_constraint where conname like 'at_partitioned%'
+  order by conname;
+           conname            |        desc        
+------------------------------+--------------------
+ at_partitioned_0_id_name_key | child 0 constraint
+ at_partitioned_1_id_name_key | child 1 constraint
+ at_partitioned_id_name_key   | parent constraint
+(3 rows)
+
+alter table at_partitioned alter column name type varchar(127);
+-- Note: these tests currently show the wrong behavior for comments :-(
+select relname,
+  c.oid = oldoid as orig_oid,
+  case relfilenode
+    when 0 then 'none'
+    when c.oid then 'own'
+    when oldfilenode then 'orig'
+    else 'OTHER'
+    end as storage,
+  obj_description(c.oid, 'pg_class') as desc
+  from pg_class c left join old_oids using (relname)
+  where relname like 'at_partitioned%'
+  order by relname;
+           relname            | orig_oid | storage |     desc     
+------------------------------+----------+---------+--------------
+ at_partitioned               | t        | own     | 
+ at_partitioned_0             | t        | own     | 
+ at_partitioned_0_id_name_key | f        | own     | parent index
+ at_partitioned_1             | t        | own     | 
+ at_partitioned_1_id_name_key | f        | own     | parent index
+ at_partitioned_id_name_key   | f        | own     | parent index
+(6 rows)
+
+select conname, obj_description(oid, 'pg_constraint') as desc
+  from pg_constraint where conname like 'at_partitioned%'
+  order by conname;
+           conname            |       desc        
+------------------------------+-------------------
+ at_partitioned_0_id_name_key | 
+ at_partitioned_1_id_name_key | 
+ at_partitioned_id_name_key   | parent constraint
+(3 rows)
+
+-- Don't remove this DROP, it exposes bug #15672
+drop table at_partitioned;
 -- disallow recursive containment of row types
 create temp table recur1 (f1 int);
 alter table recur1 add column f2 recur1; -- fails
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index d675579977..abb3a6aa13 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -1393,6 +1393,69 @@ alter table at_partitioned attach partition at_part_2 for values from (1000) to
 alter table at_partitioned alter column b type numeric using b::numeric;
 \d at_part_1
 \d at_part_2
+drop table at_partitioned;
+
+-- Alter column type when no table rewrite is required
+-- Also check that comments are preserved
+create table at_partitioned(id int, name varchar(64), unique (id, name))
+  partition by hash(id);
+comment on constraint at_partitioned_id_name_key on at_partitioned is 'parent constraint';
+comment on index at_partitioned_id_name_key is 'parent index';
+create table at_partitioned_0 partition of at_partitioned
+  for values with (modulus 2, remainder 0);
+comment on constraint at_partitioned_0_id_name_key on at_partitioned_0 is 'child 0 constraint';
+comment on index at_partitioned_0_id_name_key is 'child 0 index';
+create table at_partitioned_1 partition of at_partitioned
+  for values with (modulus 2, remainder 1);
+comment on constraint at_partitioned_1_id_name_key on at_partitioned_1 is 'child 1 constraint';
+comment on index at_partitioned_1_id_name_key is 'child 1 index';
+insert into at_partitioned values(1, 'foo');
+insert into at_partitioned values(3, 'bar');
+
+create temp table old_oids as
+  select relname, oid as oldoid, relfilenode as oldfilenode
+  from pg_class where relname like 'at_partitioned%';
+
+select relname,
+  c.oid = oldoid as orig_oid,
+  case relfilenode
+    when 0 then 'none'
+    when c.oid then 'own'
+    when oldfilenode then 'orig'
+    else 'OTHER'
+    end as storage,
+  obj_description(c.oid, 'pg_class') as desc
+  from pg_class c left join old_oids using (relname)
+  where relname like 'at_partitioned%'
+  order by relname;
+
+select conname, obj_description(oid, 'pg_constraint') as desc
+  from pg_constraint where conname like 'at_partitioned%'
+  order by conname;
+
+alter table at_partitioned alter column name type varchar(127);
+
+-- Note: these tests currently show the wrong behavior for comments :-(
+
+select relname,
+  c.oid = oldoid as orig_oid,
+  case relfilenode
+    when 0 then 'none'
+    when c.oid then 'own'
+    when oldfilenode then 'orig'
+    else 'OTHER'
+    end as storage,
+  obj_description(c.oid, 'pg_class') as desc
+  from pg_class c left join old_oids using (relname)
+  where relname like 'at_partitioned%'
+  order by relname;
+
+select conname, obj_description(oid, 'pg_constraint') as desc
+  from pg_constraint where conname like 'at_partitioned%'
+  order by conname;
+
+-- Don't remove this DROP, it exposes bug #15672
+drop table at_partitioned;
 
 -- disallow recursive containment of row types
 create temp table recur1 (f1 int);