after review fix (BUG#4067)

sql/field.cc:
  method getting maximum display length for fields
sql/field.h:
  method getting maximum display length for fields
sql/item.cc:
  code cleanup
  switch replaced with new method
sql/item.h:
  method getting maximum display length for fields

sql/field.cc

@@ -5812,3 +5812,30 @@ void Field::set_warning(const uint level, const uint code)
 			code, ER(code), field_name, thd->row_count);
   }
 }
+
+/*
+  maximum possible display length for blob
+
+  SYNOPSIS
+    Field_blob::max_length()
+
+  RETURN
+    length
+*/
+uint32 Field_blob::max_length()
+{
+  switch (packlength)
+  {
+  case 1:
+    return 255;
+  case 2:
+    return 65535;
+  case 3:
+    return 16777215;
+  case 4:
+    return (uint32)4294967295;
+  default:
+    DBUG_ASSERT(0); // we should never go here
+    return 0;
+  }
+}

sql/field.h

@@ -267,6 +267,8 @@ class Field
   void set_warning(const unsigned int level, const unsigned int code);
   virtual field_cast_enum field_cast_type()= 0;
   bool field_cast_compatible(field_cast_enum type);
+  /* maximum possible display length */
+  virtual uint32 max_length()= 0;
   friend bool reopen_table(THD *,struct st_table *,bool);
   friend int cre_myisam(my_string name, register TABLE *form, uint options,
 			ulonglong auto_increment_value);
@@ -336,6 +338,7 @@ class Field_str :public Field {
   CHARSET_INFO *charset(void) const { return field_charset; }
   void set_charset(CHARSET_INFO *charset) { field_charset=charset; }
   bool binary() const { return field_charset->state & MY_CS_BINSORT ? 1 : 0; }
+  uint32 max_length() { return field_length; }
   friend class create_field;
 };
 
@@ -366,6 +369,7 @@ class Field_decimal :public Field_num {
   void overflow(bool negative);
   bool zero_pack() const { return 0; }
   void sql_type(String &str) const;
+  uint32 max_length() { return field_length; }
   field_cast_enum field_cast_type() { return FIELD_CAST_DECIMAL; }
 };
 
@@ -397,6 +401,7 @@ class Field_tiny :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return 1; }
   void sql_type(String &str) const;
+  uint32 max_length() { return 4; }
   field_cast_enum field_cast_type() { return FIELD_CAST_TINY; }
 };
 
@@ -433,6 +438,7 @@ class Field_short :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return 2; }
   void sql_type(String &str) const;
+  uint32 max_length() { return 6; }
   field_cast_enum field_cast_type() { return FIELD_CAST_SHORT; }
 };
 
@@ -464,6 +470,7 @@ class Field_medium :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return 3; }
   void sql_type(String &str) const;
+  uint32 max_length() { return 8; }
   field_cast_enum field_cast_type() { return FIELD_CAST_MEDIUM; }
 };
 
@@ -500,6 +507,7 @@ class Field_long :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return 4; }
   void sql_type(String &str) const;
+  uint32 max_length() { return 11; }
   field_cast_enum field_cast_type() { return FIELD_CAST_LONG; }
 };
 
@@ -539,6 +547,7 @@ class Field_longlong :public Field_num {
   uint32 pack_length() const { return 8; }
   void sql_type(String &str) const;
   bool store_for_compare() { return 1; }
+  uint32 max_length() { return 20; }
   field_cast_enum field_cast_type() { return FIELD_CAST_LONGLONG; }
 };
 #endif
@@ -573,6 +582,7 @@ class Field_float :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return sizeof(float); }
   void sql_type(String &str) const;
+  uint32 max_length() { return 24; }
   field_cast_enum field_cast_type() { return FIELD_CAST_FLOAT; }
 };
 
@@ -607,6 +617,7 @@ class Field_double :public Field_num {
   void sort_string(char *buff,uint length);
   uint32 pack_length() const { return sizeof(double); }
   void sql_type(String &str) const;
+  uint32 max_length() { return 53; }
   field_cast_enum field_cast_type() { return FIELD_CAST_DOUBLE; }
 };
 
@@ -637,6 +648,7 @@ class Field_null :public Field_str {
   uint32 pack_length() const { return 0; }
   void sql_type(String &str) const;
   uint size_of() const { return sizeof(*this); }
+  uint32 max_length() { return 4; }
   field_cast_enum field_cast_type() { return FIELD_CAST_NULL; }
 };
 
@@ -1034,6 +1046,7 @@ class Field_blob :public Field_str {
   bool has_charset(void) const
   { return charset() == &my_charset_bin ? FALSE : TRUE; }
   field_cast_enum field_cast_type() { return FIELD_CAST_BLOB; }
+  uint32 max_length();
 };
 
 #ifdef HAVE_SPATIAL
@@ -1062,6 +1075,7 @@ class Field_geom :public Field_blob {
 
   void get_key_image(char *buff,uint length, CHARSET_INFO *cs,imagetype type);
   void set_key_image(char *buff,uint length, CHARSET_INFO *cs);
+  uint32 max_length() { return field_length; }
   field_cast_enum field_cast_type() { return FIELD_CAST_GEOM; }
 };
 #endif /*HAVE_SPATIAL*/

sql/item.cc

@@ -2514,53 +2514,9 @@ bool Item_type_holder::join_types(THD *thd, Item *item)
 
 uint32 Item_type_holder::real_length(Item *item)
 {
-  if (item->result_type() == STRING_RESULT)
-    return item->max_length;
   if (item->type() == Item::FIELD_ITEM)
   {
-    switch (((Item_field *)item)->field_type())
-    {
-      case MYSQL_TYPE_TINY:
-        return 4;
-      case MYSQL_TYPE_SHORT:
-        return 6;
-      case MYSQL_TYPE_LONG:
-        return 11;
-      case MYSQL_TYPE_FLOAT:
-        return 24;
-      case MYSQL_TYPE_DOUBLE:
-        return 53;
-      case MYSQL_TYPE_NULL:
-        return 4;
-      case MYSQL_TYPE_LONGLONG:
-        return 20;
-      case MYSQL_TYPE_INT24:
-        return 8;
-      case MYSQL_TYPE_TINY_BLOB:
-        return 256;
-      case MYSQL_TYPE_MEDIUM_BLOB:
-        return 65535;
-      case MYSQL_TYPE_LONG_BLOB:
-        return (uint32)4294967295;
-      case MYSQL_TYPE_BLOB:
-        return 16777215;
-      case MYSQL_TYPE_SET:
-      case MYSQL_TYPE_ENUM:
-      case MYSQL_TYPE_NEWDATE:
-      case MYSQL_TYPE_YEAR:
-      case MYSQL_TYPE_DATETIME:
-      case MYSQL_TYPE_TIME:
-      case MYSQL_TYPE_DATE:
-      case MYSQL_TYPE_TIMESTAMP:
-      case MYSQL_TYPE_DECIMAL:
-      case MYSQL_TYPE_VAR_STRING:
-      case MYSQL_TYPE_STRING:
-      case MYSQL_TYPE_GEOMETRY:
-        return item->max_length;
-      default:
-        DBUG_ASSERT(0); // we should never go there
-        return 0;
-    }
+    return ((Item_field *)item)->max_disp_length();
   }
   switch (item->result_type())
   {

sql/item.h

@@ -382,6 +382,7 @@ class Item_field :public Item_ident
   bool is_null() { return field->is_null(); }
   Item *get_tmp_table_item(THD *thd);
   void cleanup();
+  inline uint32 max_disp_length() { return field->max_length(); }
   friend class Item_default_value;
   friend class Item_insert_value;
   friend class st_select_lex_unit;