MDEV-136 Non-blocking "set read_only".

    Handle the 'set read_only=1' in lighter way, than the FLUSH TABLES READ LOCK;
    For the transactional engines we don't wait for operations on that tables to finish.

per-file comments:
 mysql-test/r/read_only_innodb.result
MDEV-136 Non-blocking "set read_only".
       test result updated.
 mysql-test/t/read_only_innodb.test
MDEV-136 Non-blocking "set read_only".
       test case added.
  sql/mysql_priv.h
MDEV-136 Non-blocking "set read_only".
        The close_cached_tables_set_readonly() declared.
  sql/set_var.cc
MDEV-136 Non-blocking "set read_only".
         Call close_cached_tables_set_readonly() for the read_only::set_var.
   sql/sql_base.cc
 MDEV-136 Non-blocking "set read_only".
         Parameters added to the close_cached_tables implementation,
         close_cached_tables_set_readonly declared.
         Prevent blocking on the transactional tables if the
         set_readonly_mode is on.

1 files changed, 29 insertions, 0 deletions

diff --git a/mysql-test/t/read_only_innodb.test b/mysql-test/t/read_only_innodb.test
index f8c25fdee1d..ec016c54f63 100644
--- a/mysql-test/t/read_only_innodb.test
+++ b/mysql-test/t/read_only_innodb.test
@@ -75,7 +75,36 @@ BEGIN;
 SELECT * FROM t1;
 COMMIT;
 
+#
+# Tests that LOCK TABLE doesn't block the SET READ_ONLY=1 for the InnoDB tables
+#
+
+connection default;
+UNLOCK TABLES;
+FLUSH STATUS;
+--echo # Expected 0 at the beginning of the test
+show status like 'Opened_tables';
+
+--echo connection con1;
+connection con1;
+lock table t1 write;
+
+--echo connection default;
 connection default;
+set global read_only=1;
+--echo # Expected 1 as the slow_log was reopened
+show status like 'Opened_tables';
+
+--echo connection con1;
+connection con1;
+unlock tables;
+
+--echo connection default;
+connection default;
+SET GLOBAL read_only=0;
+--echo # Expected 2 as the slow_log was reopened
+show status like 'Opened_tables';
+
 UNLOCK TABLES;
 DROP TABLE t1;
 DROP USER test@localhost;