Mysql increase key length

We have recently been converting most of our databases from latin to UTF-8 and have encountered issues with smaller Mysql default keylength. Mysql by default allows a max key length of 1024 size. While it was quite a bit of work to change the current data to confirm to the key length, the easier way was to recompile the Mysql source with a custom key length. Here I will detail the steps to do that:

wget http://www.percona.com/mysql/5.0.67-b7/source/mysql-5.0.67-percona-b7-src.tar.gz
tar zxf mysql-5.0.67-percona-b7-src.tar.gz

Now you'll want to make the edits to the myisam.h file to use our longer key length instead of the default 1000 byte keylength. Below is a compare of the file before and after change:

--- /tmp/myisam.h       2008-05-28 13:36:22.000000000 -0700
+++ include/myisam.h    2007-03-15 14:15:41.000000000 -0700
@@ -48,12 +49,12 @@
 #define MI_MAX_KEY                  MAX_INDEXES         /* Max allowed keys */
 #endif
 
-#define MI_MAX_POSSIBLE_KEY_BUFF    (1024+6+6)      /* For myisam_chk */
+#define MI_MAX_POSSIBLE_KEY_BUFF    (4096+6+6)      /* For myisam_chk */
 /*
   The following defines can be increased if necessary.
   But beware the dependency of MI_MAX_POSSIBLE_KEY_BUFF and MI_MAX_KEY_LENGTH.
 */
-#define MI_MAX_KEY_LENGTH           1000            /* Max length in bytes */
+#define MI_MAX_KEY_LENGTH           4000            /* Max length in bytes */
 #define MI_MAX_KEY_SEG              16              /* Max segments for key */
 
 #define MI_MAX_KEY_BUFF  (MI_MAX_KEY_LENGTH+MI_MAX_KEY_SEG*6+8+8)

Next you'll need to run configure / make install

./configure --prefix={choose a name here like /tmp/mysql_mod}
sudo make install