Bug#21505 Create view - illegal mix of collation for operation 'UNION'

The problem was that any VIEW columns had always implicit derivation.
  Fix: derivation is now copied from the original expression
  given in VIEW definition.
  For example:
  - a VIEW column which comes from a string constant
    in CREATE VIEW definition have now coercible derivation.
  - a VIEW column having COLLATE clause
    in CREATE VIEW definition have now explicit derivation.

mysql-test/r/ctype_utf8.result

@@ -1536,6 +1536,32 @@ set @a:=null;
 execute my_stmt using @a;
 a	b
 drop table if exists t1;
+drop table if exists t1;
+drop view if exists v1, v2;
+set names utf8;
+create table t1(col1 varchar(12) character set utf8 collate utf8_unicode_ci);
+insert into t1 values('t1_val');
+create view v1 as select 'v1_val' as col1;
+select coercibility(col1), collation(col1) from v1;
+coercibility(col1)	collation(col1)
+4	utf8_general_ci
+create view v2 as select col1 from v1 union select col1 from t1;
+select coercibility(col1), collation(col1)from v2;
+coercibility(col1)	collation(col1)
+2	utf8_unicode_ci
+2	utf8_unicode_ci
+drop view v1, v2;
+create view v1 as select 'v1_val' collate utf8_swedish_ci as col1;
+select coercibility(col1), collation(col1) from v1;
+coercibility(col1)	collation(col1)
+0	utf8_swedish_ci
+create view v2 as select col1 from v1 union select col1 from t1;
+select coercibility(col1), collation(col1) from v2;
+coercibility(col1)	collation(col1)
+0	utf8_swedish_ci
+0	utf8_swedish_ci
+drop view v1, v2;
+drop table t1;
 CREATE TABLE t1 (
 colA int(11) NOT NULL,
 colB varchar(255) character set utf8 NOT NULL,

mysql-test/t/ctype_utf8.test

@@ -1228,6 +1228,30 @@ set @a:=null;
 execute my_stmt using @a;
 drop table if exists t1;
 
+
+#
+# Bug#21505 Create view - illegal mix of collation for operation 'UNION'
+#
+--disable_warnings
+drop table if exists t1;
+drop view if exists v1, v2;
+--enable_warnings
+set names utf8;
+create table t1(col1 varchar(12) character set utf8 collate utf8_unicode_ci);
+insert into t1 values('t1_val');
+create view v1 as select 'v1_val' as col1;
+select coercibility(col1), collation(col1) from v1;
+create view v2 as select col1 from v1 union select col1 from t1;
+select coercibility(col1), collation(col1)from v2;
+drop view v1, v2;
+create view v1 as select 'v1_val' collate utf8_swedish_ci as col1;
+select coercibility(col1), collation(col1) from v1;
+create view v2 as select col1 from v1 union select col1 from t1;
+select coercibility(col1), collation(col1) from v2;
+drop view v1, v2;
+drop table t1;
+
+
 #
 # Bug#19960: Inconsistent results when joining
 # InnoDB tables using partial UTF8 indexes

sql/field.cc

@@ -1399,6 +1399,7 @@ Field_str::Field_str(char *ptr_arg,uint32 len_arg, uchar *null_ptr_arg,
   field_charset=charset;
   if (charset->state & MY_CS_BINSORT)
     flags|=BINARY_FLAG;
+  field_derivation= DERIVATION_IMPLICIT;
 }
 
 

sql/field.h

@@ -302,6 +302,9 @@ public:
   virtual CHARSET_INFO *sort_charset(void) const { return charset(); }
   virtual bool has_charset(void) const { return FALSE; }
   virtual void set_charset(CHARSET_INFO *charset) { }
+  virtual enum Derivation derivation(void) const
+  { return DERIVATION_IMPLICIT; }
+  virtual void set_derivation(enum Derivation derivation) { }
   bool set_warning(MYSQL_ERROR::enum_warning_level, unsigned int code,
                    int cuted_increment);
   bool check_int(const char *str, int length, const char *int_end,
@@ -373,6 +376,7 @@ public:
 class Field_str :public Field {
 protected:
   CHARSET_INFO *field_charset;
+  enum Derivation field_derivation;
 public:
   Field_str(char *ptr_arg,uint32 len_arg, uchar *null_ptr_arg,
 	    uchar null_bit_arg, utype unireg_check_arg,
@@ -387,6 +391,9 @@ public:
   uint size_of() const { return sizeof(*this); }
   CHARSET_INFO *charset(void) const { return field_charset; }
   void set_charset(CHARSET_INFO *charset) { field_charset=charset; }
+  enum Derivation derivation(void) const { return field_derivation; }
+  virtual void set_derivation(enum Derivation derivation_arg)
+  { field_derivation= derivation_arg; }
   bool binary() const { return field_charset == &my_charset_bin; }
   uint32 max_length() { return field_length; }
   friend class create_field;

sql/item.cc

@@ -1622,7 +1622,7 @@ void Item_field::set_field(Field *field_par)
   db_name= field_par->table->s->db;
   alias_name_used= field_par->table->alias_name_used;
   unsigned_flag=test(field_par->flags & UNSIGNED_FLAG);
-  collation.set(field_par->charset(), DERIVATION_IMPLICIT);
+  collation.set(field_par->charset(), field_par->derivation());
   fixed= 1;
 }
 

sql/item.h

@@ -27,19 +27,7 @@ class Item_field;
 /*
    "Declared Type Collation"
    A combination of collation and its derivation.
-*/
 
-enum Derivation
-{
-  DERIVATION_IGNORABLE= 5,
-  DERIVATION_COERCIBLE= 4,
-  DERIVATION_SYSCONST= 3,
-  DERIVATION_IMPLICIT= 2,
-  DERIVATION_NONE= 1,
-  DERIVATION_EXPLICIT= 0
-};
-
-/*
   Flags for collation aggregation modes:
   MY_COLL_ALLOW_SUPERSET_CONV  - allow conversion to a superset
   MY_COLL_ALLOW_COERCIBLE_CONV - allow conversion of a coercible value

sql/mysql_priv.h

@@ -96,6 +96,17 @@ extern CHARSET_INFO *system_charset_info, *files_charset_info ;
 extern CHARSET_INFO *national_charset_info, *table_alias_charset;
 
 
+enum Derivation
+{
+  DERIVATION_IGNORABLE= 5,
+  DERIVATION_COERCIBLE= 4,
+  DERIVATION_SYSCONST= 3,
+  DERIVATION_IMPLICIT= 2,
+  DERIVATION_NONE= 1,
+  DERIVATION_EXPLICIT= 0
+};
+
+
 typedef struct my_locale_st
 {
   const char *name;

sql/sql_select.cc

@@ -8560,6 +8560,7 @@ static Field *create_tmp_field_from_item(THD *thd, Item *item, TABLE *table,
                                      item->collation.collation);
     else
       new_field= item->make_string_field(table);
+    new_field->set_derivation(item->collation.derivation);
     break;
   case DECIMAL_RESULT:
     new_field= new Field_new_decimal(item->max_length, maybe_null, item->name,
@@ -8735,7 +8736,9 @@ Field *create_tmp_field(THD *thd, TABLE *table,Item *item, Item::Type type,
                                       (make_copy_field ? 0 : copy_func),
                                        modify_item, convert_blob_length);
   case Item::TYPE_HOLDER:  
-    return ((Item_type_holder *)item)->make_field_by_type(table);
+    result= ((Item_type_holder *)item)->make_field_by_type(table);
+    result->set_derivation(item->collation.derivation);
+    return result;
   default:					// Dosen't have to be stored
     return 0;
   }