Fixed bug mdev-473.

With the new code of mysql-5.5 for metadata locking the function
unlock_tables_n_open_system_tables_for_write should not explicitly
unlock tables for which external locks have been set and should not
explicitly reset thd->lock to 0.
 

mysql-test/r/stat_tables.result

@@ -342,4 +342,15 @@ o_orderkey	p_partkey
 set optimizer_switch=@save_optimizer_switch;
 DROP DATABASE dbt3_s001;
 use test;
+#
+# Bug mdev-473: ANALYZE table locked for write
+# 
+set use_stat_tables='complementary';
+create table t1 (i int);
+lock table t1 write;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Table is already up to date
+alter table t1 add column a varchar(8);
+drop table t1;
 set use_stat_tables=@save_use_stat_tables;

mysql-test/r/stat_tables_innodb.result

@@ -369,6 +369,17 @@ o_orderkey	p_partkey
 set optimizer_switch=@save_optimizer_switch;
 DROP DATABASE dbt3_s001;
 use test;
+#
+# Bug mdev-473: ANALYZE table locked for write
+# 
+set use_stat_tables='complementary';
+create table t1 (i int);
+lock table t1 write;
+analyze table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+alter table t1 add column a varchar(8);
+drop table t1;
 set use_stat_tables=@save_use_stat_tables;
 set optimizer_switch=@save_optimizer_switch_for_stat_tables_test;
 SET SESSION STORAGE_ENGINE=DEFAULT;

mysql-test/t/stat_tables.test

@@ -152,4 +152,19 @@ DROP DATABASE dbt3_s001;
 
 use test;
 
+--echo #
+--echo # Bug mdev-473: ANALYZE table locked for write
+--echo # 
+
+set use_stat_tables='complementary';
+
+create table t1 (i int);
+
+lock table t1 write;
+analyze table t1;
+alter table t1 add column a varchar(8);
+
+drop table t1;
+
+
 set use_stat_tables=@save_use_stat_tables;

sql/sql_base.cc

@@ -9669,10 +9669,6 @@ unlock_tables_n_open_system_tables_for_write(THD *thd,
 
   DBUG_ENTER("unlock_tables_n_open_system_tables_for_write");
 
-  if (thd->lock)
-    mysql_unlock_tables(thd, thd->lock);
-  thd->lock= 0;
-
   lex->reset_n_backup_query_tables_list(&query_tables_list_backup);
   thd->reset_n_backup_open_tables_state(backup);