Use a factory method to eliminate "results as hash" check

"Results as hash" should be set on the database, so we should only need
to check it once when we first start the query.  This patch pulls result
set construction in to a factory method on the database object.  Doing
this eliminates a "translate to hash" check that is performed on every
row fetch.

lib/sqlite3/database.rb

@@ -224,7 +224,7 @@ def execute sql, bind_vars = [], *args, &block
 
       prepare(sql) do |stmt|
         stmt.bind_params(bind_vars)
-        stmt = ResultSet.new self, stmt
+        stmt = build_result_set stmt
 
         if block
           stmt.each do |row|
@@ -746,6 +746,17 @@ def translate_from_db types, row
       @type_translator.call types, row
     end
 
+    # Given a statement, return a result set.
+    # This is not intended for general consumption
+    # :nodoc:
+    def build_result_set stmt
+      if results_as_hash
+        HashResultSet.new(self, stmt)
+      else
+        ResultSet.new(self, stmt)
+      end
+    end
+
     private
 
     NULL_TRANSLATOR = lambda { |_, row| row }

lib/sqlite3/resultset.rb

@@ -92,10 +92,6 @@ def eof?
     # For hashes, the column names are the keys of the hash, and the column
     # types are accessible via the +types+ property.
     def next
-      if @db.results_as_hash
-        return next_hash
-      end
-
       row = @stmt.step
       return nil if @stmt.done?
 
@@ -175,4 +171,8 @@ def next_hash
       row
     end
   end
+
+  class HashResultSet < ResultSet # :nodoc:
+    alias :next :next_hash
+  end
 end

lib/sqlite3/statement.rb

@@ -79,12 +79,12 @@ def execute(*bind_vars)
       reset! if active? || done?
 
       bind_params(*bind_vars) unless bind_vars.empty?
-      @results = ResultSet.new(@connection, self)
+      results = @connection.build_result_set self
 
       step if column_count == 0
 
-      yield @results if block_given?
-      @results
+      yield results if block_given?
+      results
     end
 
     # Execute the statement. If no block was given, this returns an array of

test/test_integration_resultset.rb

@@ -97,6 +97,7 @@ def test_real_translation
 
   def test_next_results_as_hash
     @db.results_as_hash = true
+    @result = @stmt.execute
     @result.reset(1)
     hash = @result.next
     assert_equal({"a" => 1, "b" => "foo"},