Prepare statement again when it is lost

If an ALTER TABLE is performed the prepared statements are lost. In this case the statement should be prepared again.

lib/cql/client/prepared_statement.rb

@@ -150,7 +150,13 @@ def self.prepare(cql, execute_options_decoder, connection_manager, logger)
       def execute(*args)
         connection = @connection_manager.random_connection
         if connection[self]
-          run(args, connection)
+          f = run(args, connection)
+          f.fallback do |e|
+            raise e unless e.is_a?(Cql::QueryError) && e.code == 0x2500 # unprepared
+            prepare(connection).flat_map do
+              run(args, connection)
+            end
+          end
         else
           prepare(connection).flat_map do
             run(args, connection)
@@ -216,11 +222,12 @@ def add_to_batch(batch, connection, bound_args)
       private
 
       def run(args, connection)
-        bound_args = args.shift(@raw_metadata.size)
-        unless bound_args.size == @raw_metadata.size && args.size <= 1
+        bound_args = args.take(@raw_metadata.size)
+        remaining_args = args.drop(@raw_metadata.size)
+        unless bound_args.size == @raw_metadata.size && remaining_args.size <= 1
           raise ArgumentError, "Expected #{@raw_metadata.size} arguments, got #{bound_args.size}"
         end
-        options = @execute_options_decoder.decode_options(args.last)
+        options = @execute_options_decoder.decode_options(remaining_args.last)
         statement_id = connection[self]
         request_metadata = @raw_result_metadata.nil?
         request = Protocol::ExecuteRequest.new(statement_id, @raw_metadata, bound_args, request_metadata, options[:consistency], options[:serial_consistency], options[:page_size], options[:paging_state], options[:trace])

spec/cql/client/prepared_statement_spec.rb

@@ -295,6 +295,25 @@ def handle_request(connection, request, timeout)
           statement.execute(11, 'hello', trace: true).value
           tracing.should be_true
         end
+
+        it 'prepares statement again when it is lost' do
+          prepare_requests = 0
+          connections.each do |c|
+            c[:num_prepare] = 0
+            c.handle_request do |r, t|
+              if r.is_a?(Protocol::ExecuteRequest) && c[:num_prepare] == 1
+                Protocol::ErrorResponse.new(0x2500, 'Unprepared')
+              else
+                if r == Protocol::PrepareRequest.new(cql)
+                  c[:num_prepare] += 1
+                end
+                handle_request(c, r, t)
+              end
+            end
+          end
+          statement.execute(11, 'hello').value
+          connections.map { |c| c[:num_prepare] }.should include(2)
+        end
       end
 
       describe '#batch' do

spec/integration/client_spec.rb

@@ -112,6 +112,13 @@ def create_keyspace_and_table
       counters = result.each_with_object({}) { |row, acc| acc[row['id']] = row['count'] }
       counters.should eql('foo' => 11, 'bar' => 3)
     end
+
+    it 'handles altered tables' do
+      result1 = statement.execute('sue')
+      client.execute('ALTER TABLE users ADD password VARCHAR')
+      result2 = statement.execute('sue')
+      result2.to_a.should eql(result1.to_a)
+    end
   end
 
   context 'with multiple connections' do