Make :encoding option work on MySQL even if config file specifies dif…

…ferent encoding (Fixes #300, again)

After discussions with tmm1, this seems like the best way to work
around the bug in libmysqlclient, which makes configuration file
settings taken from READ_DEFAULT_GROUP override an explicitly
given SET_CHARSET_NAME option.  It uses a "SET NAMES" SQL query
after connection to attempt to ensure the connection will use
the correct encoding.  This is not safe across implicit
reconnects, but Sequel hasn't used those for some time.

CHANGELOG

@@ -1,5 +1,7 @@
 === HEAD
 
+* Make :encoding option work on MySQL even if config file specifies different encoding (jeremyevans) (#300)
+
 * Don't attempt to use class polymorphism in the class_table_inheritance plugin if no cti_key is defined (jeremyevans)
 
 * Add a XmlSerializer plugin for serializing/deserializing model objects to/from XML (jeremyevans)

lib/sequel/adapters/mysql.rb

@@ -99,6 +99,11 @@ def connect(server)
         conn = Mysql.init
         conn.options(Mysql::READ_DEFAULT_GROUP, opts[:config_default_group] || "client")
         conn.options(Mysql::OPT_LOCAL_INFILE, opts[:config_local_infile]) if opts.has_key?(:config_local_infile)
+        if encoding = opts[:encoding] || opts[:charset]
+          # Set encoding before connecting so that the mysql driver knows what
+          # encoding we want to use, but this can be overridden by READ_DEFAULT_GROUP.
+          conn.options(Mysql::SET_CHARSET_NAME, encoding)
+        end
         conn.real_connect(
           opts[:host] || 'localhost',
           opts[:user],
@@ -110,11 +115,11 @@ def connect(server)
           Mysql::CLIENT_MULTI_STATEMENTS +
           (opts[:compress] == false ? 0 : Mysql::CLIENT_COMPRESS)
         )
-        if encoding = opts[:encoding] || opts[:charset]
-          # Setting encoding before the connect appears not to work
-          # with READ_DEFAULT_GROUP, so set it afterwards.
-          conn.options(Mysql::SET_CHARSET_NAME, encoding)
-        end
+        # Set encoding a slightly different way after connecting,
+        # in case the READ_DEFAULT_GROUP overrode the provided encoding.
+        # Doesn't work across implicit reconnects, but Sequel doesn't turn on
+        # that feature.
+        conn.query("set names #{literal(encoding.to_s)}") if encoding
 
         # increase timeout so mysql server doesn't disconnect us
         conn.query("set @@wait_timeout = #{opts[:timeout] || 2592000}")