MDEV-31957 Concurrent ALTER and ANALYZE collecting statistics can result in stale statistical data

Fixed hang when renaming index to original name

mysql-test/main/analyze.result

@@ -382,5 +382,40 @@ ALTER TABLE t1 DROP KEY idx;
 ERROR HY000: Cannot drop index 'idx': needed in a foreign key constraint
 DROP TABLE t1;
 #
+# Check index rename where name is not changed
+#
+create or replace table t1 (a int primary key, b int, c int, key b (b,c));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) NOT NULL,
+  `b` int(11) DEFAULT NULL,
+  `c` int(11) DEFAULT NULL,
+  PRIMARY KEY (`a`),
+  KEY `b` (`b`,`c`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+analyze table t1 persistent for all;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	Table is already up to date
+select * from mysql.index_stats where table_name= "t1";
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	t1	PRIMARY	1	1.0000
+test	t1	b	1	NULL
+test	t1	b	2	NULL
+alter ignore table t1 rename key `b` to b, LOCK=shared;
+select * from mysql.index_stats where table_name= "t1";
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	t1	PRIMARY	1	1.0000
+test	t1	b	1	NULL
+test	t1	b	2	NULL
+alter ignore table t1 rename key `b` to `B`, LOCK=shared;
+select * from mysql.index_stats where table_name= "t1";
+db_name	table_name	index_name	prefix_arity	avg_frequency
+test	t1	PRIMARY	1	1.0000
+test	t1	B	1	NULL
+test	t1	B	2	NULL
+drop table t1;
+#
 # End of 10.6 tests
 #

mysql-test/main/analyze.test

@@ -254,6 +254,21 @@ SELECT index_name FROM mysql.index_stats WHERE table_name = 't1' order by index_
 --error ER_DROP_INDEX_FK
 ALTER TABLE t1 DROP KEY idx;
 DROP TABLE t1;
+
+--echo #
+--echo # Check index rename where name is not changed
+--echo #
+
+create or replace table t1 (a int primary key, b int, c int, key b (b,c));
+show create table t1;
+analyze table t1 persistent for all;
+select * from mysql.index_stats where table_name= "t1";
+alter ignore table t1 rename key `b` to b, LOCK=shared;
+select * from mysql.index_stats where table_name= "t1";
+alter ignore table t1 rename key `b` to `B`, LOCK=shared;
+select * from mysql.index_stats where table_name= "t1";
+drop table t1;
+
 --echo #
 --echo # End of 10.6 tests
 --echo #

sql/sql_table.cc

@@ -8298,9 +8298,13 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
         }
 
         key_name= rename_key->new_name.str;     // New name of current key_info
-        rename_key_it.remove();
+        if (cmp(&rename_key->old_name, &rename_key->new_name))
+        {
+          /* Key was renamed */
           alter_info->add_stat_rename_index(key_info, &rename_key->new_name,
                                             thd->mem_root);
+        }
+        rename_key_it.remove();
 
         /*
           If the user has explicitly renamed the key, we should no longer