1. sys_variables[] array is removed.

2. All have_xxx variables are now selectable.


sql/set_var.cc:
  1. sys_have_xxx variables added.
  2. Removed sys_var *sys_variables[] array as we don't need it any more.
  3. void set_var_init() changed to use sys_var_xxx chain insted of sys_variables[] array.
sql/set_var.h:
  1. add_sys_var() method added to the sys_var class. It's called from constructors
  to chain all successor objects. The first one is stored in the 'static sys_var *first'.
  The total number of variables is in the 'static uint sys_vars'. Each sys_var successor object
  has the 'sys_var *next' pointer to the next one in the chain. 
  2. sys_var_have_variable class introduced to make all have_xxx variables selectable.
sql/sql_lex.cc:
  trg_new_row_fake_var(0, 0) replaced with '(sys_var*) 0x01' as we don't want to have such fake variables in the sys_var_xxx chain.
sql/sql_lex.h:
  Proper use of the changed trg_new_row_fake_var.
sql/sql_yacc.yy:
  Proper use of the changed trg_new_row_fake_var.

sql/set_var.h

@@ -39,6 +39,9 @@ typedef byte *(*sys_value_ptr_func)(THD *thd);
 class sys_var
 {
 public:
+  static sys_var *first;
+  static uint sys_vars;
+  sys_var *next;
   struct my_option *option_limits;	/* Updated by by set_var_init() */
   uint name_length;			/* Updated by by set_var_init() */
   const char *name;
@@ -48,12 +51,18 @@ class sys_var
   sys_var(const char *name_arg)
     :name(name_arg), after_update(0)
     , no_support_one_shot(1)
-    {}
+  { add_sys_var(); }
   sys_var(const char *name_arg,sys_after_update_func func)
     :name(name_arg), after_update(func)
     , no_support_one_shot(1)
-  {}
+  { add_sys_var(); }
   virtual ~sys_var() {}
+  void add_sys_var()
+  {
+    next= first;
+    first= this;
+    sys_vars++;
+  }
   virtual bool check(THD *thd, set_var *var);
   bool check_enum(THD *thd, set_var *var, TYPELIB *enum_names);
   bool check_set(THD *thd, set_var *var, TYPELIB *enum_names);
@@ -701,6 +710,30 @@ class sys_var_readonly: public sys_var
   bool is_readonly() const { return 1; }
 };
 
+
+class sys_var_have_variable: public sys_var
+{
+  SHOW_COMP_OPTION *have_variable;
+
+public:
+  sys_var_have_variable(const char *variable_name,
+                        SHOW_COMP_OPTION *have_variable_arg):
+    sys_var(variable_name),
+    have_variable(have_variable_arg)
+  { }
+  byte *value_ptr(THD *thd, enum_var_type type, LEX_STRING *base)
+  {
+    return (byte*) show_comp_option_name[*have_variable];
+  }
+  bool update(THD *thd, set_var *var) { return 1; }
+  bool check_default(enum_var_type type) { return 1; }
+  bool check_type(enum_var_type type) { return type != OPT_GLOBAL; }
+  bool check_update_type(Item_result type) { return 1; }
+  SHOW_TYPE type() { return SHOW_CHAR; }
+  bool is_readonly() const { return 1; }
+};
+
+
 class sys_var_thd_time_zone :public sys_var_thd
 {
 public:

sql/sql_lex.cc

@@ -28,7 +28,8 @@
   We are using pointer to this variable for distinguishing between assignment
   to NEW row field (when parsing trigger definition) and structured variable.
 */
-sys_var_long_ptr trg_new_row_fake_var(0, 0);
+
+sys_var *trg_new_row_fake_var= (sys_var*) 0x01;
 
 /* Macros to look like lex */
 

sql/sql_lex.h

@@ -702,7 +702,7 @@ struct st_trg_chistics
   enum trg_event_type event;
 };
 
-extern sys_var_long_ptr trg_new_row_fake_var;
+extern sys_var *trg_new_row_fake_var;
 
 enum xa_option_words {XA_NONE, XA_JOIN, XA_RESUME, XA_ONE_PHASE,
                       XA_SUSPEND, XA_FOR_MIGRATE};

sql/sql_yacc.yy

@@ -8529,7 +8529,7 @@ sys_option_value:
         {
           LEX *lex=Lex;
 
-          if ($2.var == &trg_new_row_fake_var)
+          if ($2.var == trg_new_row_fake_var)
           {
             /* We are in trigger and assigning value to field of new row */
             Item *it;
@@ -8750,7 +8750,7 @@ internal_variable_name:
                 YYABORT;
               }
               /* This special combination will denote field of NEW row */
-              $$.var= &trg_new_row_fake_var;
+              $$.var= trg_new_row_fake_var;
               $$.base_name= $3;
             }
             else