diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index 8bfb2ad958..4928702aec 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -965,9 +965,6 @@ compute_index_stats(Relation onerel, double totalrows,
 			for (i = 0; i < attr_cnt; i++)
 			{
 				VacAttrStats *stats = thisdata->vacattrstats[i];
-				AttributeOpts *aopt =
-				get_attribute_options(stats->attr->attrelid,
-									  stats->attr->attnum);
 
 				stats->exprvals = exprvals + i;
 				stats->exprnulls = exprnulls + i;
@@ -977,14 +974,6 @@ compute_index_stats(Relation onerel, double totalrows,
 									 numindexrows,
 									 totalindexrows);
 
-				/*
-				 * If the n_distinct option is specified, it overrides the
-				 * above computation.  For indices, we always use just
-				 * n_distinct, not n_distinct_inherited.
-				 */
-				if (aopt != NULL && aopt->n_distinct != 0.0)
-					stats->stadistinct = aopt->n_distinct;
-
 				MemoryContextResetAndDeleteChildren(col_context);
 			}
 		}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 9322829b23..99b70d223d 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -4491,7 +4491,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			break;
 		case AT_SetOptions:		/* ALTER COLUMN SET ( options ) */
 		case AT_ResetOptions:	/* ALTER COLUMN RESET ( options ) */
-			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_INDEX | ATT_FOREIGN_TABLE);
+			ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_FOREIGN_TABLE);
 			/* This command never recurses */
 			pass = AT_PASS_MISC;
 			break;
diff --git a/src/test/regress/expected/btree_index.out b/src/test/regress/expected/btree_index.out
index bc113a70b4..c7328b1dc4 100644
--- a/src/test/regress/expected/btree_index.out
+++ b/src/test/regress/expected/btree_index.out
@@ -329,3 +329,15 @@ INSERT INTO delete_test_table SELECT i, 1, 2, 3 FROM generate_series(1,1000) i;
 -- Test unsupported btree opclass parameters
 create index on btree_tall_tbl (id int4_ops(foo=1));
 ERROR:  operator class int4_ops has no options
+-- Test case of ALTER INDEX with abuse of column names for indexes.
+-- This grammar is not officially supported, but the parser allows it.
+CREATE INDEX btree_tall_idx2 ON btree_tall_tbl (id);
+ALTER INDEX btree_tall_idx2 ALTER COLUMN id SET (n_distinct=100);
+ERROR:  "btree_tall_idx2" is not a table, materialized view, or foreign table
+DROP INDEX btree_tall_idx2;
+-- Partitioned index
+CREATE TABLE btree_part (id int4) PARTITION BY RANGE (id);
+CREATE INDEX btree_part_idx ON btree_part(id);
+ALTER INDEX btree_part_idx ALTER COLUMN id SET (n_distinct=100);
+ERROR:  "btree_part_idx" is not a table, materialized view, or foreign table
+DROP TABLE btree_part;
diff --git a/src/test/regress/sql/btree_index.sql b/src/test/regress/sql/btree_index.sql
index c60312db2d..c34502249f 100644
--- a/src/test/regress/sql/btree_index.sql
+++ b/src/test/regress/sql/btree_index.sql
@@ -172,3 +172,14 @@ INSERT INTO delete_test_table SELECT i, 1, 2, 3 FROM generate_series(1,1000) i;
 
 -- Test unsupported btree opclass parameters
 create index on btree_tall_tbl (id int4_ops(foo=1));
+
+-- Test case of ALTER INDEX with abuse of column names for indexes.
+-- This grammar is not officially supported, but the parser allows it.
+CREATE INDEX btree_tall_idx2 ON btree_tall_tbl (id);
+ALTER INDEX btree_tall_idx2 ALTER COLUMN id SET (n_distinct=100);
+DROP INDEX btree_tall_idx2;
+-- Partitioned index
+CREATE TABLE btree_part (id int4) PARTITION BY RANGE (id);
+CREATE INDEX btree_part_idx ON btree_part(id);
+ALTER INDEX btree_part_idx ALTER COLUMN id SET (n_distinct=100);
+DROP TABLE btree_part;