如何使用Datastax Java驱动程序的异步/批量写入function
我打算使用Datastax Java驱动程序写入Cassandra ..我主要对Datastax java驱动程序的Batch Writes和Asycnhronousfunction感兴趣，但我无法获得任何可以解释如何在我的下面的代码中包含这些function的教程它使用Datastax Java驱动程序..
/** * Performs an upsert of the specified attributes for the specified id. */ public void upsertAttributes(final String userId, final Map attributes, final String columnFamily) { try { // make a sql here using the above input parameters. String sql = sqlPart1.toString()+sqlPart2.toString(); DatastaxConnection.getInstance(); PreparedStatement prepStatement = DatastaxConnection.getSession().prepare(sql); prepStatement.setConsistencyLevel(ConsistencyLevel.ONE); BoundStatement query = prepStatement.bind(userId, attributes.values().toArray(new Object[attributes.size()])); DatastaxConnection.getSession().execute(query); } catch (InvalidQueryException e) { LOG.error("Invalid Query Exception in DatastaxClient::upsertAttributes "+e); } catch (Exception e) { LOG.error("Exception in DatastaxClient::upsertAttributes "+e); } }
在下面的代码中，我使用Datastax Java驱动程序创建了与Cassandra节点的连接。
/** * Creating Cassandra connection using Datastax Java driver * */ private DatastaxConnection() { try{ builder = Cluster.builder(); builder.addContactPoint("some_nodes"); builder.poolingOptions().setCoreConnectionsPerHost( HostDistance.LOCAL, builder.poolingOptions().getMaxConnectionsPerHost(HostDistance.LOCAL)); cluster = builder .withRetryPolicy(DowngradingConsistencyRetryPolicy.INSTANCE) .withReconnectionPolicy(new ConstantReconnectionPolicy(100L)) .build(); StringBuilder s = new StringBuilder(); Set allHosts = cluster.getMetadata().getAllHosts(); for (Host h : allHosts) { s.append("["); s.append(h.getDatacenter()); s.append(h.getRack()); s.append(h.getAddress()); s.append("]"); } System.out.println("Cassandra Cluster: " + s.toString()); session = cluster.connect("testdatastaxks"); } catch (NoHostAvailableException e) { e.printStackTrace(); throw new RuntimeException(e); } catch (Exception e) { } }
任何人都可以帮助我如何将批量写入或异步function添加到我的上述代码..感谢您的帮助..
我正在运行Cassandra 1.2.9
对于asynch，它就像使用executeAsync函数一样简单：
... DatastaxConnection.getSession().executeAsync(query);
对于批处理，您需要构建查询（我使用字符串，因为编译器知道如何优化字符串连接）：
String cql = "BEGIN BATCH " cql += "INSERT INTO test.prepared (id, col_1) VALUES (?,?); "; cql += "INSERT INTO test.prepared (id, col_1) VALUES (?,?); "; cql += "APPLY BATCH; " DatastaxConnection.getInstance(); PreparedStatement prepStatement = DatastaxConnection.getSession().prepare(cql); prepStatement.setConsistencyLevel(ConsistencyLevel.ONE); // this is where you need to be careful // bind expects a comma separated list of values for all the params (?) above // so for the above batch we need to supply 4 params: BoundStatement query = prepStatement.bind(userId, "col1_val", userId_2, "col1_val_2"); DatastaxConnection.getSession().execute(query);
在旁注中，我认为您对语句的绑定可能看起来像这样，假设您将属性更改为映射列表，其中每个映射表示批处理中的更新/插入：
BoundStatement query = prepStatement.bind(userId, attributesList.get(0).values().toArray(new Object[attributes.size()]), userId_2, attributesList.get(1).values().toArray(new Object[attributes.size()]));
对于Lyuben的答案中提供的示例，使用字符串设置类似Type.COUNTER （如果需要更新计数器）的批处理的某些属性将不起作用。 相反，您可以批量安排准备好的语句，如下所示：
final String insertQuery = "INSERT INTO test.prepared (id, col_1) VALUES (?,?);"; final PreparedStatement prepared = session.prepare(insertQuery); final BatchStatement batch = new BatchStatement(BatchStatement.Type.UNLOGGED); batch.add(prepared.bind(userId1, "something")); batch.add(prepared.bind(userId2, "another")); batch.add(prepared.bind(userId3, "thing")); session.executeAsync(batch);