Fix for bug #20695: Charset introducer overrides charset definition for column.

  - if there are two character set definitions in the column declaration,
    we replace the first one with the second one as we store both in the LEX->charset
    slot. Add a separate slot to the LEX structure to store underscore charset.
  - convert default values to the column charset of STRING, VARSTRING fields 
    if necessary as well.

mysql-test/r/ctype_recoding.result

@@ -247,3 +247,14 @@ lpad(c1,3,'
 select rpad(c1,3,''), rpad('',3,c1) from t1;
 rpad(c1,3,'')	rpad('',3,c1)
 	
+drop table t1;
+set names koi8r;
+create table t1(a char character set cp1251 default _koi8r 0xFF);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` char(1) character set cp1251 default ''
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+create table t1(a char character set latin1 default _cp1251 0xFF);
+ERROR 42000: Invalid default value for 'a'

mysql-test/t/ctype_recoding.test

@@ -186,5 +186,17 @@ select rpad(c1,3,'
 # TODO
 #select case c1 when '' then '' when '' then '' else 'c' end from t1;
 #select export_set(5,c1,''), export_set(5,'',c1) from t1;
+drop table t1;
+
+#
+# Bug 20695: problem with field default value's character set
+#
+
+set names koi8r;
+create table t1(a char character set cp1251 default _koi8r 0xFF);
+show create table t1;
+drop table t1;
+--error 1067
+create table t1(a char character set latin1 default _cp1251 0xFF);
 
 # End of 4.1 tests

sql/sql_lex.cc

@@ -643,7 +643,8 @@ int yylex(void *arg, void *yythd)
       */
 
       if ((yylval->lex_str.str[0]=='_') && 
-          (lex->charset=get_charset_by_csname(yylval->lex_str.str+1,
+          (lex->underscore_charset=
+             get_charset_by_csname(yylval->lex_str.str + 1,
                                    MY_CS_PRIMARY,MYF(0))))
         return(UNDERSCORE_CHARSET);
       return(result_state);			// IDENT or IDENT_QUOTED

sql/sql_lex.h

@@ -613,7 +613,7 @@ typedef struct st_lex
   LEX_USER *grant_user;
   gptr yacc_yyss,yacc_yyvs;
   THD *thd;
-  CHARSET_INFO *charset;
+  CHARSET_INFO *charset, *underscore_charset;
 
   List<key_part_spec> col_list;
   List<key_part_spec> ref_list;

sql/sql_table.cc

@@ -516,6 +516,40 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
       DBUG_RETURN(-1);
     }
 
+    /*
+      Convert the default value character
+      set into the column character set if necessary.
+    */
+    if (sql_field->def && 
+        savecs != sql_field->def->collation.collation &&
+        (sql_field->sql_type == FIELD_TYPE_VAR_STRING ||
+         sql_field->sql_type == FIELD_TYPE_STRING ||
+         sql_field->sql_type == FIELD_TYPE_SET ||
+         sql_field->sql_type == FIELD_TYPE_ENUM))
+    {
+      Item_arena backup_arena;
+      bool need_to_change_arena=
+        !thd->current_arena->is_conventional_execution();
+      if (need_to_change_arena)
+      {
+        /* Assert that we don't do that at every PS execute */
+        DBUG_ASSERT(thd->current_arena->is_first_stmt_execute());
+        thd->set_n_backup_item_arena(thd->current_arena, &backup_arena);
+      }
+
+      sql_field->def= sql_field->def->safe_charset_converter(savecs);
+
+      if (need_to_change_arena)
+        thd->restore_backup_item_arena(thd->current_arena, &backup_arena);
+
+      if (sql_field->def == NULL)
+      {
+        /* Could not convert */
+        my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
+        DBUG_RETURN(-1);
+      }
+    }
+
     if (sql_field->sql_type == FIELD_TYPE_SET ||
         sql_field->sql_type == FIELD_TYPE_ENUM)
     {
@@ -580,35 +614,6 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
         sql_field->interval_list.empty(); // Don't need interval_list anymore
       }
 
-      /*
-        Convert the default value from client character
-        set into the column character set if necessary.
-      */
-      if (sql_field->def && cs != sql_field->def->collation.collation)
-      {
-        Item_arena backup_arena;
-        bool need_to_change_arena=
-          !thd->current_arena->is_conventional_execution();
-        if (need_to_change_arena)
-        {
-          /* Asser that we don't do that at every PS execute */
-          DBUG_ASSERT(thd->current_arena->is_first_stmt_execute());
-          thd->set_n_backup_item_arena(thd->current_arena, &backup_arena);
-        }
-
-        sql_field->def= sql_field->def->safe_charset_converter(cs);
-
-        if (need_to_change_arena)
-          thd->restore_backup_item_arena(thd->current_arena, &backup_arena);
-
-        if (sql_field->def == NULL)
-        {
-          /* Could not convert */
-          my_error(ER_INVALID_DEFAULT, MYF(0), sql_field->field_name);
-          DBUG_RETURN(-1);
-        }
-      }
-
       if (sql_field->sql_type == FIELD_TYPE_SET)
       {
         if (sql_field->def != NULL)

sql/sql_yacc.yy

@@ -4896,7 +4896,7 @@ text_literal:
 	| NCHAR_STRING
 	{ $$=  new Item_string($1.str,$1.length,national_charset_info); }
 	| UNDERSCORE_CHARSET TEXT_STRING
-	  { $$ = new Item_string($2.str,$2.length,Lex->charset); }
+	  { $$ = new Item_string($2.str,$2.length,Lex->underscore_charset); }
 	| text_literal TEXT_STRING_literal
 	  { ((Item_string*) $1)->append($2.str,$2.length); }
 	;
@@ -4963,7 +4963,7 @@ literal:
 	      (String*) 0;
 	    $$= new Item_string(str ? str->ptr() : "",
 				str ? str->length() : 0,
-				Lex->charset);
+				Lex->underscore_charset);
 	  }
 	| DATE_SYM text_literal { $$ = $2; }
 	| TIME_SYM text_literal { $$ = $2; }