MDEV-15971 Split the code for CHARACTER_OCTET_LENGTH and CHARACTER_MAXIMUM_LENGTH into methods in Field

sql/field.cc

@@ -10997,6 +10997,12 @@ Column_definition::redefine_stage1_common(const Column_definition *dup_field,
 */
 
 uint32 Field_blob::char_length() const
+{
+  return Field_blob::octet_length();
+}
+
+
+uint32 Field_blob::octet_length() const
 {
   switch (packlength)
   {

sql/field.h

@@ -1121,6 +1121,11 @@ public:
   {
     return Information_schema_numeric_attributes();
   }
+  virtual Information_schema_character_attributes
+            information_schema_character_attributes() const
+  {
+    return Information_schema_character_attributes();
+  }
   /*
     Caller beware: sql_type can change str.Ptr, so check
     ptr() to see if it changed if you are using your own buffer
@@ -1731,6 +1736,13 @@ public:
   enum Derivation derivation(void) const { return field_derivation; }
   bool binary() const { return field_charset == &my_charset_bin; }
   uint32 max_display_length() const { return field_length; }
+  uint32 char_length() const { return field_length / field_charset->mbmaxlen; }
+  Information_schema_character_attributes
+    information_schema_character_attributes() const
+  {
+    return Information_schema_character_attributes(field_length,
+                                                   char_length());
+  }
   friend class Create_field;
   my_decimal *val_decimal(my_decimal *);
   bool val_bool() { return val_real() != 0e0; }
@@ -2424,6 +2436,11 @@ public:
 	       unireg_check_arg, field_name_arg, collation)
     {}
   const Type_handler *type_handler() const { return &type_handler_null; }
+  Information_schema_character_attributes
+    information_schema_character_attributes() const
+  {
+    return Information_schema_character_attributes();
+  }
   Copy_func *get_copy_func(const Field *from) const
   {
     return do_field_string;
@@ -3564,6 +3581,13 @@ public:
   }
   enum ha_base_keytype key_type() const
     { return binary() ? HA_KEYTYPE_VARBINARY2 : HA_KEYTYPE_VARTEXT2; }
+  Information_schema_character_attributes
+    information_schema_character_attributes() const
+  {
+    uint32 octets= Field_blob::octet_length();
+    uint32 chars= octets / field_charset->mbminlen;
+    return Information_schema_character_attributes(octets, chars);
+  }
   Copy_func *get_copy_func(const Field *from) const
   {
     /*
@@ -3726,6 +3750,7 @@ public:
   { return charset() == &my_charset_bin ? FALSE : TRUE; }
   uint32 max_display_length() const;
   uint32 char_length() const;
+  uint32 octet_length() const;
   uint is_equal(Create_field *new_field);
 private:
   int save_field_metadata(uchar *first_byte);
@@ -3808,6 +3833,11 @@ public:
   {
     return MYSQL_TYPE_GEOMETRY;
   }
+  Information_schema_character_attributes
+    information_schema_character_attributes() const
+  {
+    return Information_schema_character_attributes();
+  }
   bool can_optimize_range(const Item_bool_func *cond,
                                   const Item *item,
                                   bool is_eq_func) const;

sql/sql_show.cc

@@ -5635,7 +5635,6 @@ err:
 static void store_column_type(TABLE *table, Field *field, CHARSET_INFO *cs,
                               uint offset)
 {
-  bool is_blob;
   const char *tmp_buff;
   char column_type_buff[MAX_FIELD_WIDTH];
   String column_type(column_type_buff, sizeof(column_type_buff), cs);
@@ -5661,22 +5660,18 @@ static void store_column_type(TABLE *table, Field *field, CHARSET_INFO *cs,
                               (tmp_buff ? (uint)(tmp_buff - column_type.ptr()) :
                                column_type.length()), cs);
 
-  is_blob= (field->type() == MYSQL_TYPE_BLOB);
-  if (field->has_charset() || is_blob ||
-      field->real_type() == MYSQL_TYPE_VARCHAR ||  // For varbinary type
-      field->real_type() == MYSQL_TYPE_STRING)     // For binary type
+  Information_schema_character_attributes cattr=
+    field->information_schema_character_attributes();
+  if (cattr.has_char_length())
   {
-    uint32 octet_max_length= field->max_display_length();
-    if (is_blob && octet_max_length != (uint32) UINT_MAX32)
-      octet_max_length /= field->charset()->mbmaxlen;
-    longlong char_max_len= is_blob ? 
-      (longlong) octet_max_length / field->charset()->mbminlen :
-      (longlong) octet_max_length / field->charset()->mbmaxlen;
     /* CHARACTER_MAXIMUM_LENGTH column*/
-    table->field[offset + 1]->store(char_max_len, TRUE);
+    table->field[offset + 1]->store((longlong) cattr.char_length(), true);
     table->field[offset + 1]->set_notnull();
+  }
+  if (cattr.has_octet_length())
+  {
     /* CHARACTER_OCTET_LENGTH column */
-    table->field[offset + 2]->store((longlong) octet_max_length, TRUE);
+    table->field[offset + 2]->store((longlong) cattr.octet_length(), true);
     table->field[offset + 2]->set_notnull();
   }
 

sql/sql_type.h

@@ -951,6 +951,34 @@ public:
 };
 
 
+class Information_schema_character_attributes
+{
+  uint32 m_octet_length;
+  uint32 m_char_length;
+  bool m_is_set;
+public:
+  Information_schema_character_attributes()
+   :m_octet_length(0), m_char_length(0), m_is_set(false)
+  { }
+  Information_schema_character_attributes(uint32 octet_length,
+                                          uint32 char_length)
+   :m_octet_length(octet_length), m_char_length(char_length), m_is_set(true)
+  { }
+  bool has_octet_length() const { return m_is_set; }
+  bool has_char_length() const { return m_is_set; }
+  uint32 octet_length() const
+  {
+    DBUG_ASSERT(has_octet_length());
+    return m_octet_length;
+  }
+  uint char_length() const
+  {
+    DBUG_ASSERT(has_char_length());
+    return m_char_length;
+  }
+};
+
+
 class Type_handler
 {
 protected: