Index: src/wp-admin/includes/schema.php
===================================================================
--- src/wp-admin/includes/schema.php	(revision 28187)
+++ src/wp-admin/includes/schema.php	(working copy)
@@ -101,7 +101,8 @@
   KEY comment_post_ID (comment_post_ID),
   KEY comment_approved_date_gmt (comment_approved,comment_date_gmt),
   KEY comment_date_gmt (comment_date_gmt),
-  KEY comment_parent (comment_parent)
+  KEY comment_parent (comment_parent),
+  KEY comment_author_email(comment_author_email(10))
 ) $charset_collate;
 CREATE TABLE $wpdb->links (
   link_id bigint(20) unsigned NOT NULL auto_increment,
Index: src/wp-includes/version.php
===================================================================
--- src/wp-includes/version.php	(revision 28187)
+++ src/wp-includes/version.php	(working copy)
@@ -11,7 +11,7 @@
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 27916;
+$wp_db_version = 27917;
 
 /**
  * Holds the TinyMCE version