Hex escape blob input on MySQL

This doesn't appear to be necessary on the MySQL side, but if you
mix utf-8 input strings and blobs in the same string on ruby 1.9+,
you can end up with encoding errors on the ruby side.  Hex encoding
the blobs can work around that, and doesn't appear to cause an harm
other than bloating the SQL string used.  Performance sensitive
code should be using prepared statements for large blob input
anyway, so that doesn't seem like a major downside.

Author: jeremyevans

CHANGELOG

@@ -1,5 +1,7 @@
 === HEAD
 
+* Hex escape blob input on MySQL (jeremyevans)
+
 * Handle more disconnect errors when using the postgres adapter with the postgres-pr driver (jeremyevans)
 
 * Model#setter_methods private method now accepts 1 argument instead of 2 (jeremyevans)

lib/sequel/adapters/shared/mysql.rb

@@ -563,6 +563,8 @@ module DatasetMethods
       EXPLAIN_EXTENDED = 'EXPLAIN EXTENDED '.freeze
       BACKSLASH_RE = /\\/.freeze
       QUAD_BACKSLASH = "\\\\\\\\".freeze
+      BLOB_START = "0x".freeze
+      HSTAR = "H*".freeze
 
       # MySQL specific syntax for LIKE/REGEXP searches, as well as
       # string concatenation.
@@ -893,6 +895,11 @@ def limit_sql(sql)
       alias delete_limit_sql limit_sql
       alias update_limit_sql limit_sql
 
+      # MySQL uses a preceding X for hex escaping strings
+      def literal_blob_append(sql, v)
+        sql << BLOB_START << v.unpack(HSTAR).first
+      end
+
       # Use 0 for false on MySQL
       def literal_false
         BOOL_FALSE