Fix for bug #29131: SHOW VARIABLES reports variable 'log' but SET

doesn't recognize it

This is a 5.0 version of the patch, it will be null-merged to 5.1

Problem:

'log' and 'log_slow_queries' were "fixed" variables, i.e. they showed up
in SHOW VARIABLES, but could not be used in expressions like 
"select @@log". Also, using them in the SET statement produced an 
incorrect "unknown system variable" error.

Solution:

Make 'log' and 'log_slow_queries' read-only dynamic variables to make 
them available for use in expressions, and produce a correct error 
about the variable being read-only when used in the SET statement.


mysql-test/r/variables.result:
  Added a test case for bug #29131.
mysql-test/t/variables.test:
  Added a test case for bug #29131.
sql/mysql_priv.h:
  Changed the type of opt_log and opt_slow_log to my_bool to 
  align with the interfaces in set_var.cc
sql/mysqld.cc:
  Changed the type of opt_log and opt_slow_log to my_bool to 
  align with the interfaces in set_var.cc
sql/set_var.cc:
  Made 'log' and 'log_slow_queries' to be read-only dynamic system 
  variable, i.e. available for use in expressions with the @@var syntax.
sql/set_var.h:
  Added a new system variable class representing a read-only boolean
  variable.

1 files changed, 16 insertions, 0 deletions

diff --git a/mysql-test/r/variables.result b/mysql-test/r/variables.result
index 3d76f8e4a90..217be9400e6 100644
--- a/mysql-test/r/variables.result
+++ b/mysql-test/r/variables.result
@@ -791,6 +791,22 @@ ERROR HY000: Variable 'hostname' is a read only variable
 show variables like 'hostname';
 Variable_name	Value
 hostname	#
+SHOW VARIABLES LIKE 'log';
+Variable_name	Value
+log	ON
+SELECT @@log;
+@@log
+1
+SET GLOBAL log=0;
+ERROR HY000: Variable 'log' is a read only variable
+SHOW VARIABLES LIKE 'log_slow_queries';
+Variable_name	Value
+log_slow_queries	ON
+SELECT @@log_slow_queries;
+@@log_slow_queries
+1
+SET GLOBAL log_slow_queries=0;
+ERROR HY000: Variable 'log_slow_queries' is a read only variable
 End of 5.0 tests
 set global binlog_cache_size         =@my_binlog_cache_size;
 set global connect_timeout           =@my_connect_timeout;