Ticket #4853: mysql_key_length.df

Index: test/migration_test.rb
===================================================================
--- test/migration_test.rb      (revision 4347)
+++ test/migration_test.rb      (working copy)
@@ -50,6 +50,7 @@
       Person.connection.add_column "people", "last_name", :string        
       Person.connection.add_column "people", "administrator", :boolean
       Person.connection.add_column "people", "key", :string
+      Person.connection.add_column "people", "longtext", :text
       
       assert_nothing_raised { Person.connection.add_index("people", "last_name") }
       assert_nothing_raised { Person.connection.remove_index("people", "last_name") }
@@ -61,6 +62,10 @@
       assert_nothing_raised { Person.connection.add_index("people", ["key"], :name => "key", :unique => true) }
       assert_nothing_raised { Person.connection.remove_index("people", :name => "key", :unique => true) }
 
+      # key length
+      assert_nothing_raised { Person.connection.add_index("people", ["longtext"], :name => "longtext", :limit => {"longtext" => 10}) }
+      assert_nothing_raised { Person.connection.remove_index("people", :name => "longtext") }
+
       # Sybase adapter does not support indexes on :boolean columns
       unless current_adapter?(:SybaseAdapter)
         assert_nothing_raised { Person.connection.add_index("people", %w(last_name first_name administrator), :name => "named_admin") }
Index: lib/active_record/connection_adapters/abstract/schema_statements.rb
===================================================================
--- lib/active_record/connection_adapters/abstract/schema_statements.rb (revision 4347)
+++ lib/active_record/connection_adapters/abstract/schema_statements.rb (working copy)
@@ -190,11 +190,17 @@
         if Hash === options # legacy support, since this param was a string
           index_type = options[:unique] ? "UNIQUE" : ""
           index_name = options[:name] || index_name
+          limit = {}
+          if options.include?(:limit) && self.supports_subkey_length?
+            options[:limit].each do |col, lim|
+              limit[col] = lim
+            end
+          end 
         else
           index_type = options
         end
         quoted_column_names = column_names.map { |e| quote_column_name(e) }.join(", ")
-        execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{table_name} (#{quoted_column_names})"
+        execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{table_name} (#{column_names.collect do |col| "#{quote_column_name(col)}#{limit.include?(col) ? "(#{limit[col]})" : ""}" end.join(", ")})"
       end
 
       # Remove the given index from the table.
Index: lib/active_record/connection_adapters/abstract/schema_definitions.rb
===================================================================
--- lib/active_record/connection_adapters/abstract/schema_definitions.rb        (revision 4347)
+++ lib/active_record/connection_adapters/abstract/schema_definitions.rb        (working copy)
@@ -162,7 +162,15 @@
         end
     end
 
-    class IndexDefinition < Struct.new(:table, :name, :unique, :columns) #:nodoc:
+    class IndexDefinition
+      attr_accessor :table, :name, :unique, :columns, :limit
+      def initialize(table, name, unique, columns, limit = {})
+        @table = table
+        @name = name
+        @unique = unique
+        @columns = columns
+        @limit = limit
+      end
     end
 
     class ColumnDefinition < Struct.new(:base, :name, :type, :limit, :default, :null) #:nodoc:
Index: lib/active_record/connection_adapters/abstract_adapter.rb
===================================================================
--- lib/active_record/connection_adapters/abstract_adapter.rb   (revision 4347)
+++ lib/active_record/connection_adapters/abstract_adapter.rb   (working copy)
@@ -39,7 +39,15 @@
       def supports_migrations?
         false
       end
-      
+
+      #
+      # Does this adapter support subkey length in CREATE INDEX statements?
+      # Ex: CREATE INDEX users_name_index ON users (name(20))
+      #      
+      def supports_subkey_length?
+        false
+      end
+
       # Does this adapter support using DISTINCT within COUNT?  This is +true+
       # for all adapters except sqlite.
       def supports_count_distinct?
Index: lib/active_record/connection_adapters/mysql_adapter.rb
===================================================================
--- lib/active_record/connection_adapters/mysql_adapter.rb      (revision 4347)
+++ lib/active_record/connection_adapters/mysql_adapter.rb      (working copy)
@@ -80,6 +80,10 @@
         "MySQL server has gone away"
       ]
 
+      def supports_subkey_length?
+        true
+      end
+
       def initialize(connection, logger, connection_options, config)
         super(connection, logger)
         @connection_options, @config = connection_options, config
@@ -274,13 +278,16 @@
       def indexes(table_name, name = nil)#:nodoc:
         indexes = []
         current_index = nil
+        limit = {}
         execute("SHOW KEYS FROM #{table_name}", name).each do |row|
           if current_index != row[2]
             next if row[2] == "PRIMARY" # skip the primary key
             current_index = row[2]
             indexes << IndexDefinition.new(row[0], row[2], row[1] == "0", [])
           end
-
+          if !row[7].nil?
+            indexes.last.limit[row[4]] = row[7].to_i
+          end
           indexes.last.columns << row[4]
         end
         indexes
Index: lib/active_record/schema_dumper.rb
===================================================================
--- lib/active_record/schema_dumper.rb  (revision 4347)
+++ lib/active_record/schema_dumper.rb  (working copy)
@@ -127,6 +127,7 @@
         indexes.each do |index|
           stream.print "  add_index #{index.table.inspect}, #{index.columns.inspect}, :name => #{index.name.inspect}"
           stream.print ", :unique => true" if index.unique
+          stream.print ", :limit => {#{index.limit.keys.collect do |key| "\"#{key}\" => #{index.limit[key]}" end.join(", ")}}" if !index.limit.empty?
           stream.puts
         end
         stream.puts unless indexes.empty?