A fix for Bug#22891 "session level max_allowed_packet can be

set but is ignored".
                                  
This patch makes @@session.max_allowed_packed and
@@session.net_buffer_length read-only as suggested in the bug
report. The user will have to use SET GLOBAL (and reconnect)
to alter the session values of these variables.
                            
The error string ER_VARIABLE_IS_READONLY is introduced.
                            
Tests are modified accordingly.


sql/set_var.cc:
  The class sys_var_thd_ulong_session_readonly is introduced as
  a specialization of sys_var_thd_ulong implementing a read-only
  session variable. The class overrides check() and
  check_default() to achieve the read-only property for the
  session part of the variable.
sql/set_var.h:
  The class sys_var_thd_ulong_session_readonly is introduced as
  a specialization of sys_var_thd_ulong implementing a read-only
  session variable. The class overrides check() and
  check_default() to achieve the read-only property for the
  session part of the variable.
sql/share/errmsg.txt:
  New error ER_VARIABLE_IS_READONLY.

1 files changed, 4 insertions, 1 deletions

diff --git a/mysql-test/t/func_compress.test b/mysql-test/t/func_compress.test
index 68f07f258bf..7f17fd2180f 100644
--- a/mysql-test/t/func_compress.test
+++ b/mysql-test/t/func_compress.test
@@ -43,8 +43,11 @@ drop table t1;
 # note that when LOW_MEMORY is set the "test" below is meaningless
 #
 
-set @@max_allowed_packet=1048576*100;
+set @@global.max_allowed_packet=1048576*100;
 --replace_result "''" XXX "'1'" XXX
+
+# reconnect to make the new max packet size take effect
+--connect (newconn, localhost, root,,)
 eval select compress(repeat('aaaaaaaaaa', IF('$LOW_MEMORY', 10, 10000000))) is null;
 
 #