MDEV-8095 Split Create_field

Part2: moving a few other fields from Column_definition to Create_field.
sizeof(sp_variable) is now 200 bytes (vs 248 bytes in 10.1)

sql/field.cc

@@ -9757,7 +9757,6 @@ void Column_definition::init_for_tmp_table(enum_field_types sql_type_arg,
                        FLAGSTR(pack_flag, FIELDFLAG_DECIMAL),
                        f_packtype(pack_flag)));
   vcol_info= 0;
-  create_if_not_exists= FALSE;
 
   DBUG_VOID_RETURN;
 }
@@ -10429,7 +10428,6 @@ Field *make_field(TABLE_SHARE *share,
 Column_definition::Column_definition(THD *thd, Field *old_field,
                                                Field *orig_field)
 {
-  field=      old_field;
   field_name= old_field->field_name;
   length=     old_field->field_length;
   flags=      old_field->flags;
@@ -10441,7 +10439,6 @@ Column_definition::Column_definition(THD *thd, Field *old_field,
   comment=    old_field->comment;
   decimals=   old_field->decimals();
   vcol_info=  old_field->vcol_info;
-  create_if_not_exists= FALSE;
   option_list= old_field->option_list;
   option_struct= old_field->option_struct;
 

sql/field.h

@@ -3440,20 +3440,15 @@ class Column_definition: public Sql_alloc
   uint  decimals, flags, pack_length, key_length;
   Field::utype unireg_check;
   TYPELIB *interval;			// Which interval to use
-  TYPELIB *save_interval;               // Temporary copy for the above
-                                        // Used only for UCS2 intervals
   List<String> interval_list;
   CHARSET_INFO *charset;
   uint32 srid;
   Field::geometry_type geom_type;
-  Field *field;				// For alter table
   engine_option_value *option_list;
   /** structure with parsed options (for comparing fields in ALTER TABLE) */
   ha_field_option_struct *option_struct;
 
-  uint8 interval_id;                    // For rea_create_table
-  uint	offset,pack_flag;
-  bool create_if_not_exists;            // Used in ALTER TABLE IF NOT EXISTS
+  uint pack_flag;
 
   /* 
     This is additinal data provided for any computed(virtual) field.
@@ -3467,8 +3462,8 @@ class Column_definition: public Sql_alloc
     def(0), on_update(0), sql_type(MYSQL_TYPE_NULL),
     flags(0), pack_length(0), key_length(0), interval(0),
     srid(0), geom_type(Field::GEOM_GEOMETRY),
-    field(0), option_list(NULL), option_struct(NULL),
-    create_if_not_exists(false), vcol_info(0)
+    option_list(NULL), option_struct(NULL),
+    vcol_info(0)
   {
     interval_list.empty();
   }
@@ -3518,12 +3513,21 @@ class Create_field :public Column_definition
 public:
   const char *change;			// If done with alter table
   const char *after;			// Put column after this one
+  Field *field;				// For alter table
+  TYPELIB *save_interval;               // Temporary copy for the above
+                                        // Used only for UCS2 intervals
+  uint	offset;
+  uint8 interval_id;                    // For rea_create_table
+  bool create_if_not_exists;            // Used in ALTER TABLE IF NOT EXISTS
+
   Create_field():
-    Column_definition(), change(0), after(0)
+    Column_definition(), change(0), after(0),
+    field(0), create_if_not_exists(false)
   { }
   Create_field(THD *thd, Field *old_field, Field *orig_field):
     Column_definition(thd, old_field, orig_field),
-    change(old_field->field_name), after(0)
+    change(old_field->field_name), after(0),
+    field(old_field), create_if_not_exists(false)
   { }
   /* Used to make a clone of this object for ALTER/CREATE TABLE */
   Create_field *clone(MEM_ROOT *mem_root) const;

sql/sql_yacc.yy

@@ -867,7 +867,6 @@ void LEX::init_last_field(Column_definition *field, const char *field_name,
 void LEX::set_last_field_type(const Lex_field_type_st &type)
 {
   last_field->sql_type= type.field_type();
-  last_field->create_if_not_exists= check_exists;
   last_field->charset= charset;
 
   if (type.length())
@@ -6150,6 +6149,7 @@ field_spec:
 
             lex->alter_info.create_list.push_back($$, thd->mem_root);
 
+            $$->create_if_not_exists= Lex->check_exists;
             if ($$->flags & PRI_KEY_FLAG)
               add_key_to_list(lex, &$1, Key::PRIMARY, Lex->check_exists);
             else if ($$->flags & UNIQUE_KEY_FLAG)