Fixed bug#17530: Incorrect key truncation on table creation caused server crash.

When a too long field is used for a key, only a prefix part of the field is 
used. Length is reduced to the max key length allowed for storage. But if the
field have a multibyte charset it is possible to break multibyte char
sequence. This leads to the failed assertion in the innodb code and 
server crash when a record is inserted.

The make_prepare_table() now aligns truncated key length to the boundary of
multibyte char.


mysql-test/t/create.test:
  Added test case for bug#17530: Incorrect key truncation on table creation caused server crash.
mysql-test/r/create.result:
  Added test case for bug#17530: Incorrect key truncation on table creation caused server crash.
sql/sql_table.cc:
  Fixed bug#17530: Incorrect key truncation on table creation caused server crash.
  The make_prepare_table() now aligns truncated key length to the boundary of
  multibyte char.

mysql-test/r/create.result

@@ -765,3 +765,9 @@ t1	CREATE TABLE `t1` (
   `i` int(11) default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1 MAX_ROWS=4294967295
 drop table t1;
+create table t1(f1 varchar(800) binary not null, key(f1)) engine = innodb 
+character set utf8 collate utf8_general_ci;
+Warnings:
+Warning	1071	Specified key was too long; max key length is 765 bytes
+insert into t1 values('aaa');
+drop table t1;

mysql-test/t/create.test

@@ -660,4 +660,12 @@ alter table t1 max_rows=100000000000;
 show create table t1;
 drop table t1;
 
+#
+# Bug#17530: Incorrect key truncation on table creation caused server crash.
+#
+create table t1(f1 varchar(800) binary not null, key(f1)) engine = innodb 
+  character set utf8 collate utf8_general_ci;
+insert into t1 values('aaa');
+drop table t1;
+
 # End of 5.0 tests

sql/sql_table.cc

@@ -1299,7 +1299,9 @@ static int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
       }
       if (length > file->max_key_part_length() && key->type != Key::FULLTEXT)
       {
-	length=file->max_key_part_length();
+        length= file->max_key_part_length();
+        /* Align key length to multibyte char boundary */
+        length-= length % sql_field->charset->mbmaxlen;
 	if (key->type == Key::MULTIPLE)
 	{
 	  /* not a critical problem */