ctype_utf8.result, ctype_utf8.test, mi_key.c:

  bug 4521: unique key prefix interacts poorly with utf8: fixed length key fix.


myisam/mi_key.c:
  bug 4521: unique key prefix interacts poorly with utf8: fixed length key fix.
mysql-test/t/ctype_utf8.test:
  bug 4521: unique key prefix interacts poorly with utf8: fixed length key fix.
mysql-test/r/ctype_utf8.result:
  bug 4521: unique key prefix interacts poorly with utf8: fixed length key fix.

myisam/mi_key.c

@@ -168,13 +168,18 @@ uint _mi_make_key(register MI_INFO *info, uint keynr, uchar *key,
       }
       continue;
     }
-#ifdef NOT_YET_FIXED_LENGTH_KEY
     if (char_length && length > char_length)
     {
       char_length= my_charpos(cs, pos, pos+length, char_length);
-      set_if_smaller(length, char_length);
+      if (char_length < length)
+      {
+        uint diff= length - char_length;
+        memcpy((byte*) key, pos, char_length);
+        cs->cset->fill(cs, key + char_length, diff, ' ');
+        key+= length;
+        continue;
+      }
     }
-#endif
     memcpy((byte*) key, pos, length);
     key+= length;
   }

mysql-test/r/ctype_utf8.result

@@ -276,3 +276,26 @@ select c cb20 from t1 where c=repeat('b',20);
 cb20
 bbbbbbbbbbbbbbbbbbbb
 drop table t1;
+create table t1 (c char(3) character set utf8, unique (c(2)));
+insert into t1 values ('1'),('2'),('3'),('4'),('x'),('y'),('z');
+insert into t1 values ('a');
+insert into t1 values ('aa');
+insert into t1 values ('aaa');
+ERROR 23000: Duplicate entry 'aaa' for key 1
+insert into t1 values ('b');
+insert into t1 values ('bb');
+insert into t1 values ('bbb');
+ERROR 23000: Duplicate entry 'bbb' for key 1
+insert into t1 values ('а');
+insert into t1 values ('аа');
+insert into t1 values ('ааа');
+ERROR 23000: Duplicate entry 'ааа' for key 1
+insert into t1 values ('б');
+insert into t1 values ('бб');
+insert into t1 values ('ббб');
+ERROR 23000: Duplicate entry 'ббб' for key 1
+insert into t1 values ('ꪪ');
+insert into t1 values ('ꪪꪪ');
+insert into t1 values ('ꪪꪪꪪ');
+ERROR 23000: Duplicate entry 'ꪪꪪ' for key 1
+drop table t1;

mysql-test/t/ctype_utf8.test

@@ -187,3 +187,30 @@ select c cz from t1 where c='z';
 select c ca10 from t1 where c='aaaaaaaaaa';
 select c cb20 from t1 where c=repeat('b',20);
 drop table t1;
+
+#
+# Bug 4521: unique key prefix interacts poorly with utf8
+# Check fixed length keys
+create table t1 (c char(3) character set utf8, unique (c(2)));
+insert into t1 values ('1'),('2'),('3'),('4'),('x'),('y'),('z');
+insert into t1 values ('a');
+insert into t1 values ('aa');
+--error 1062
+insert into t1 values ('aaa');
+insert into t1 values ('b');
+insert into t1 values ('bb');
+--error 1062
+insert into t1 values ('bbb');
+insert into t1 values ('а');
+insert into t1 values ('аа');
+--error 1062
+insert into t1 values ('ааа');
+insert into t1 values ('б');
+insert into t1 values ('бб');
+--error 1062
+insert into t1 values ('ббб');
+insert into t1 values ('ꪪ');
+insert into t1 values ('ꪪꪪ');
+--error 1062
+insert into t1 values ('ꪪꪪꪪ');
+drop table t1;