5 files changed, 60 insertions, 7 deletions
diff --git a/mysql-test/suite/parts/inc/part_alter_values.inc b/mysql-test/suite/parts/inc/part_alter_values.inc
index ac69169a9ca..20f3e063ba1 100644
--- a/mysql-test/suite/parts/inc/part_alter_values.inc
+++ b/mysql-test/suite/parts/inc/part_alter_values.inc
@@ -36,12 +36,20 @@ ALTER TABLE t1 REORGANIZE PARTITION p1 INTO
 );
 DROP TABLE t1;
 
-#
-# MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION
-#
+--echo #
+--echo # MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION
+--echo #
 --eval create table t1 (i int) engine=$engine partition by range(i) (partition p0 values less than (10))
 lock table t1 write;
 --error ER_SAME_NAME_PARTITION
 alter table t1 add partition (partition p0 values less than (20));
 alter table t1 add partition (partition p1 values less than (20)) /* comment */;
 drop table t1;
+
+--echo #
+--echo # MDEV-26127 Assertion `err != DB_DUPLICATE_KEY' failed or InnoDB: Failing assertion: id != 0 on ALTER ... REBUILD PARTITION
+--echo #
+--eval CREATE TABLE t1 (c INT) ENGINE=$engine PARTITION BY KEY(c) PARTITIONS 4;
+LOCK TABLES t1 WRITE, t1 AS a READ;
+ALTER TABLE t1 REBUILD PARTITION p0;
+DROP TABLE t1;
diff --git a/mysql-test/suite/parts/r/partition_alter_innodb.result b/mysql-test/suite/parts/r/partition_alter_innodb.result
index f3921a1db26..5d02ce4c00e 100644
--- a/mysql-test/suite/parts/r/partition_alter_innodb.result
+++ b/mysql-test/suite/parts/r/partition_alter_innodb.result
@@ -42,9 +42,19 @@ PARTITION p3 VALUES IN (4,5,6)
 );
 ERROR HY000: Syntax error: LIST PARTITIONING requires definition of VALUES IN for each partition
 DROP TABLE t1;
+#
+# MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION
+#
 create table t1 (i int) engine=InnoDB partition by range(i) (partition p0 values less than (10));
 lock table t1 write;
 alter table t1 add partition (partition p0 values less than (20));
 ERROR HY000: Duplicate partition name p0
 alter table t1 add partition (partition p1 values less than (20)) /* comment */;
 drop table t1;
+#
+# MDEV-26127 Assertion `err != DB_DUPLICATE_KEY' failed or InnoDB: Failing assertion: id != 0 on ALTER ... REBUILD PARTITION
+#
+CREATE TABLE t1 (c INT) ENGINE=InnoDB PARTITION BY KEY(c) PARTITIONS 4;;
+LOCK TABLES t1 WRITE, t1 AS a READ;
+ALTER TABLE t1 REBUILD PARTITION p0;
+DROP TABLE t1;
diff --git a/mysql-test/suite/parts/r/partition_alter_maria.result b/mysql-test/suite/parts/r/partition_alter_maria.result
index 77f511d9b3b..a49639482c0 100644
--- a/mysql-test/suite/parts/r/partition_alter_maria.result
+++ b/mysql-test/suite/parts/r/partition_alter_maria.result
@@ -69,9 +69,19 @@ PARTITION p3 VALUES IN (4,5,6)
 );
 ERROR HY000: Syntax error: LIST PARTITIONING requires definition of VALUES IN for each partition
 DROP TABLE t1;
+#
+# MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION
+#
 create table t1 (i int) engine=Aria partition by range(i) (partition p0 values less than (10));
 lock table t1 write;
 alter table t1 add partition (partition p0 values less than (20));
 ERROR HY000: Duplicate partition name p0
 alter table t1 add partition (partition p1 values less than (20)) /* comment */;
 drop table t1;
+#
+# MDEV-26127 Assertion `err != DB_DUPLICATE_KEY' failed or InnoDB: Failing assertion: id != 0 on ALTER ... REBUILD PARTITION
+#
+CREATE TABLE t1 (c INT) ENGINE=Aria PARTITION BY KEY(c) PARTITIONS 4;;
+LOCK TABLES t1 WRITE, t1 AS a READ;
+ALTER TABLE t1 REBUILD PARTITION p0;
+DROP TABLE t1;
diff --git a/mysql-test/suite/parts/r/partition_alter_myisam.result b/mysql-test/suite/parts/r/partition_alter_myisam.result
index ce3e04d6c97..afbb4c21353 100644
--- a/mysql-test/suite/parts/r/partition_alter_myisam.result
+++ b/mysql-test/suite/parts/r/partition_alter_myisam.result
@@ -42,12 +42,22 @@ PARTITION p3 VALUES IN (4,5,6)
 );
 ERROR HY000: Syntax error: LIST PARTITIONING requires definition of VALUES IN for each partition
 DROP TABLE t1;
+#
+# MDEV-15456 Server crashes upon adding or dropping a partition in ALTER under LOCK TABLE after ER_SAME_NAME_PARTITION
+#
 create table t1 (i int) engine=MyISAM partition by range(i) (partition p0 values less than (10));
 lock table t1 write;
 alter table t1 add partition (partition p0 values less than (20));
 ERROR HY000: Duplicate partition name p0
 alter table t1 add partition (partition p1 values less than (20)) /* comment */;
 drop table t1;
+#
+# MDEV-26127 Assertion `err != DB_DUPLICATE_KEY' failed or InnoDB: Failing assertion: id != 0 on ALTER ... REBUILD PARTITION
+#
+CREATE TABLE t1 (c INT) ENGINE=MyISAM PARTITION BY KEY(c) PARTITIONS 4;;
+LOCK TABLES t1 WRITE, t1 AS a READ;
+ALTER TABLE t1 REBUILD PARTITION p0;
+DROP TABLE t1;
 create table t1 ( c1 int, c2 int, c3 varchar(100)) delay_key_write=1
 partition by key(c1) (
 partition p01 data directory = 'MYSQL_TMP_DIR'
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index 2334286b039..2453e0da159 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -1,5 +1,5 @@
 /* Copyright (c) 2005, 2017, Oracle and/or its affiliates.
-   Copyright (c) 2009, 2018, MariaDB
+   Copyright (c) 2009, 2022, MariaDB
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -6408,13 +6408,28 @@ static void alter_partition_lock_handling(ALTER_PARTITION_PARAM_TYPE *lpt)
 
 static int alter_close_table(ALTER_PARTITION_PARAM_TYPE *lpt)
 {
+  TABLE_SHARE *share= lpt->table->s;
+  char key[MAX_DBKEY_LENGTH];
+  size_t key_length= share->table_cache_key.length;
+  memcpy(key, share->table_cache_key.str, key_length);
+  int error= 0;
   DBUG_ENTER("alter_close_table");
 
   if (lpt->table->db_stat)
   {
-    mysql_lock_remove(lpt->thd, lpt->thd->lock, lpt->table);
-    lpt->table->file->ha_close();
-    lpt->table->db_stat= 0;                        // Mark file closed
+    for (TABLE *table= lpt->thd->open_tables; table; (table= table->next))
+    {
+      if (table->s->table_cache_key.length == key_length &&
+          !memcmp(table->s->table_cache_key.str, key, key_length))
+      {
+        mysql_lock_remove(lpt->thd, lpt->thd->lock, table);
+        if ((error= table->file->ha_close()))
+        {
+          DBUG_RETURN(error);
+        }
+        table->db_stat= 0; // Mark file closed
+      }
+    }
   }
   DBUG_RETURN(0);
 }