Bug#20575529 PERFORMANCE_SCHEMA.GLOBAL_VARIABLES MYSTERY DEPRECATION

WARNING

The following query
  SELECT * from performance_schema.global_variables;
displays a deprecation warning related to the global variable 'sql_log_bin',
because of special logic implemented for this very variable for backward
compatibility reasons.

See the resolution of
  Bug#67433 Using SET GLOBAL SQL_LOG_BIN should not be allowed
for details.

This fix filters out explicitly variable 'sql_log_bin'
from table performance_schema.global_variables because:
- this variable is not intended to be global,
- there is no need to preserve backward compatibility
for this table since it is new, unlike the existing
table INFORMATION_SCHEMA.global_variables.

(cherry picked from commit 56f6154ed5ae5cb51f658000d4af2725d2129f55)

Author: marcalff

mysql-test/suite/perfschema/r/show_sanity.result

@@ -123,8 +123,6 @@ Warning	1287	'INFORMATION_SCHEMA.SESSION_VARIABLES' is deprecated and will be re
 insert into test.sanity
 select "5.7", "P_S.GLOBAL_VARIABLES", variable_name
 from performance_schema.global_variables;
-Warnings:
-Warning	1287	'@@global.sql_log_bin' is deprecated and will be removed in a future release. Please use the constant 1 (since @@global.sql_log_bin is always equal to 1) instead
 
 # STEP 2-4
 insert into test.sanity
@@ -283,6 +281,7 @@ where show_mode = "5.7"
     and source = "P_S.GLOBAL_VARIABLES")
 order by show_mode, source, variable_name;
 SHOW_MODE	SOURCE	VARIABLE_NAME
+5.6	I_S.GLOBAL_VARIABLES	SQL_LOG_BIN
 
 ================================================================================
 TEST 3

storage/perfschema/pfs_variable.cc

@@ -120,9 +120,40 @@ int PFS_system_variable_cache::do_materialize_global(void)
   for (Show_var_array::iterator show_var= m_show_var_array.begin();
        show_var->value && (show_var != m_show_var_array.end()); show_var++)
   {
+    const char* name= show_var->name;
     sys_var *value= (sys_var *)show_var->value;
     DBUG_ASSERT(value);
 
+    if ((m_query_scope == OPT_GLOBAL) &&
+        (!my_strcasecmp(system_charset_info, name, "sql_log_bin")))
+    {
+      /*
+        PLEASE READ:
+        http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-6.html
+
+        SQL_LOG_BIN is:
+        - declared in sys_vars.cc as both GLOBAL and SESSION in 5.7
+        - impossible to SET with SET GLOBAL (raises an error)
+        - and yet can be read with @@global.sql_log_bin
+
+        When show_compatibility_56 = ON,
+        - SHOW GLOBAL VARIABLES does expose a row for SQL_LOG_BIN
+        - INFORMATION_SCHEMA.GLOBAL_VARIABLES also does expose a row,
+        both are for backward compatibility of existing applications,
+        so that no application logic change is required.
+
+        Now, with show_compatibility_56 = OFF (aka, in this code)
+        - SHOW GLOBAL VARIABLES does -- not -- expose a row for SQL_LOG_BIN
+        - PERFORMANCE_SCHEMA.GLOBAL_VARIABLES also does -- not -- expose a row
+        so that a clean interface is exposed to (upgraded and modified) applications.
+
+        The assert below will fail once SQL_LOG_BIN really is defined
+        as SESSION_ONLY (in 5.8), so that this special case can be removed.
+      */
+      DBUG_ASSERT(value->scope() == sys_var::SESSION);
+      continue;
+    }
+
     /* Match the system variable scope to the target scope. */
     if (match_scope(value->scope()))
     {