2 files changed, 63 insertions, 0 deletions
diff --git a/mysql-test/suite/innodb/r/innodb-alter-debug.result b/mysql-test/suite/innodb/r/innodb-alter-debug.result
index 4644c124a45..519283536d5 100644
--- a/mysql-test/suite/innodb/r/innodb-alter-debug.result
+++ b/mysql-test/suite/innodb/r/innodb-alter-debug.result
@@ -107,3 +107,29 @@ ALTER TABLE t RENAME INDEX i2 to x, ALGORITHM=INPLACE;
 ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
 SET DEBUG_DBUG = @saved_debug_dbug;
 DROP TABLE t;
+#
+# MDEV-26772 InnoDB DDL fails with DUPLICATE KEY error
+#
+create table t1(f1 int not null primary key,
+f2 int not null, index idx(f2))engine=innodb;
+insert into t1 values(1, 1);
+connect con1,localhost,root,,,;
+SET DEBUG_SYNC='before_delete_table_stats SIGNAL blocked WAIT_FOR go';
+SET innodb_lock_wait_timeout=0;
+ALTER TABLE t1 FORCE, ALGORITHM=COPY;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR blocked';
+BEGIN;
+SELECT * FROM mysql.innodb_table_stats FOR UPDATE;
+database_name	table_name	last_update	n_rows	clustered_index_size	sum_of_other_index_sizes
+SET DEBUG_SYNC='now SIGNAL go';
+connection con1;
+connection default;
+COMMIT;
+SET DEBUG_SYNC=RESET;
+connection con1;
+ALTER TABLE t1 RENAME KEY idx TO idx1, ALGORITHM=COPY;
+disconnect con1;
+connection default;
+DROP TABLE t1;
+# End of 10.6 tests
diff --git a/mysql-test/suite/innodb/t/innodb-alter-debug.test b/mysql-test/suite/innodb/t/innodb-alter-debug.test
index 7fbbb3159ee..7af8e882724 100644
--- a/mysql-test/suite/innodb/t/innodb-alter-debug.test
+++ b/mysql-test/suite/innodb/t/innodb-alter-debug.test
@@ -142,5 +142,42 @@ SET DEBUG_DBUG = @saved_debug_dbug;
 
 DROP TABLE t;
 
+--echo #
+--echo # MDEV-26772 InnoDB DDL fails with DUPLICATE KEY error
+--echo #
+
+create table t1(f1 int not null primary key,
+
+                f2 int not null, index idx(f2))engine=innodb;
+
+insert into t1 values(1, 1);
+
+connect(con1,localhost,root,,,);
+SET DEBUG_SYNC='before_delete_table_stats SIGNAL blocked WAIT_FOR go';
+SET innodb_lock_wait_timeout=0;
+send ALTER TABLE t1 FORCE, ALGORITHM=COPY;
+
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR blocked';
+BEGIN;
+SELECT * FROM mysql.innodb_table_stats FOR UPDATE;
+SET DEBUG_SYNC='now SIGNAL go';
+
+connection con1;
+reap;
+
+connection default;
+COMMIT;
+SET DEBUG_SYNC=RESET;
+
+connection con1;
+ALTER TABLE t1 RENAME KEY idx TO idx1, ALGORITHM=COPY;
+disconnect con1;
+
+connection default;
+DROP TABLE t1;
+
+--echo # End of 10.6 tests
+
 # Wait till all disconnects are completed
 --source include/wait_until_count_sessions.inc