Implement skipSome method for RemoteBlock.

arangod/Aql/ExecutionBlock.cpp

@@ -4041,7 +4041,60 @@ AqlItemBlock* RemoteBlock::getSome (size_t atLeast,
 ////////////////////////////////////////////////////////////////////////////////
 
 size_t RemoteBlock::skipSome (size_t atLeast, size_t atMost) {
-  return 0;
+  // For every call we simply forward via HTTP
+
+  ClusterComm* cc = ClusterComm::instance();
+  std::unique_ptr<ClusterCommResult> res;
+
+  // Later, we probably want to set these sensibly:
+  ClientTransactionID const clientTransactionId = "AQL";
+  CoordTransactionID const coordTransactionId = 1;
+
+  Json body(Json::Array, 2);
+  body("atLeast", Json(static_cast<double>(atLeast)))
+      ("atMost", Json(static_cast<double>(atMost)));
+  std::string bodyString(body.toString());
+  std::map<std::string, std::string> headers;
+
+  res.reset(cc->syncRequest(clientTransactionId,
+                            coordTransactionId,
+                            _server,
+                            rest::HttpRequest::HTTP_REQUEST_PUT,
+                            std::string("/_db/") 
+                              + _engine->getTransaction()->vocbase()->_name
+                              + "/_api/aql/skipSome/" + _queryId,
+                            bodyString,
+                            headers,
+                            3600.0));
+
+  if (res->status == CL_COMM_TIMEOUT) {
+    // No reply, we give up:
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_CLUSTER_TIMEOUT,
+           "timeout in cluster AQL operation");
+  }
+  if (res->status == CL_COMM_ERROR) {
+    // This could be a broken connection or an Http error:
+    if (res->result == nullptr || ! res->result->isComplete()) {
+      // there is no result
+      THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_CLUSTER_CONNECTION_LOST,
+             "lost connection within cluster");
+    }
+    // In this case a proper HTTP error was reported by the DBserver,
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_CLUSTER_AQL_COMMUNICATION);
+  }
+
+  // If we get here, then res->result is the response which will be
+  // a serialized AqlItemBlock:
+  StringBuffer const& responseBodyBuf(res->result->getBody());
+  Json responseBodyJson(TRI_UNKNOWN_MEM_ZONE,
+                        TRI_JsonString(TRI_UNKNOWN_MEM_ZONE, 
+                                       responseBodyBuf.begin()));
+  if (JsonHelper::getBooleanValue(responseBodyJson.json(), "error", true)) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_CLUSTER_AQL_COMMUNICATION);
+  }
+  size_t skipped = JsonHelper::getNumericValue<size_t>(responseBodyJson.json(),
+                                                       "skipped", 0);
+  return skipped;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

arangod/Aql/RestAqlHandler.cpp

@@ -483,7 +483,8 @@ void RestAqlHandler::useQuery (std::string const& operation,
                     "skipSome lead to an exception");
       return;
     }
-    answerBody("skipped", Json(static_cast<double>(skipped)));
+    answerBody("skipped", Json(static_cast<double>(skipped)))
+              ("error", Json(false));
   }
   else if (operation == "skip") {
     auto number = JsonHelper::getNumericValue<uint64_t>(queryJson.json(),