Bug#46922: crash when adding partitions and open_files_limit

is reached

Problem was bad error handling, leaving some new temporary
partitions locked and initialized and some not yet initialized
and locked, leading to a crash when trying to unlock the not
yet initialized and locked partitions

Solution was to unlock the already locked partitions, and not
include any of the new temporary partitions in later unlocks

mysql-test/r/partition_open_files_limit.result

+DROP TABLE IF EXISTS `t1`;
+# Bug#46922: crash when adding partitions and open_files_limit is reached
+CREATE TABLE t1 (a INT PRIMARY KEY) 
+ENGINE=MyISAM PARTITION BY KEY () PARTITIONS 1;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11);
+# if the bug exists, then crash will happen here
+ALTER TABLE t1 ADD PARTITION PARTITIONS 511;
+ERROR HY000: Out of resources when opening file '<partition file>' (Errcode: 24)
+SELECT * FROM t1;
+a
+1
+10
+11
+2
+3
+4
+5
+6
+7
+8
+9
+DROP TABLE t1;

mysql-test/t/partition_open_files_limit-master.opt

+--open-files-limit=5 --max_connections=2 --table_open_cache=1

mysql-test/t/partition_open_files_limit.test

+--source include/have_partition.inc
+
+--disable_warnings
+DROP TABLE IF EXISTS `t1`;
+--enable_warnings
+
+#
+--echo # Bug#46922: crash when adding partitions and open_files_limit is reached
+#
+CREATE TABLE t1 (a INT PRIMARY KEY) 
+ENGINE=MyISAM PARTITION BY KEY () PARTITIONS 1;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11);
+--echo # if the bug exists, then crash will happen here
+--replace_regex /file '.*'/file '<partition file>'/
+--error 23
+ALTER TABLE t1 ADD PARTITION PARTITIONS 511;
+--sorted_result
+SELECT * FROM t1;
+DROP TABLE t1;

sql/ha_partition.cc

@@ -1280,10 +1280,10 @@ void ha_partition::cleanup_new_partition(uint part_count)
     m_file= m_added_file;
     m_added_file= NULL;
 
+    external_lock(ha_thd(), F_UNLCK);
     /* delete_table also needed, a bit more complex */
     close();
 
-    m_added_file= m_file;
     m_file= save_m_file;
   }
   DBUG_VOID_RETURN;