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Neptune OpenPher 中的交易
Amazon Neptune 中的 OpenPher 实施使用Neptune 定义的交易语义但是，Bolt 驱动程序提供的隔离级别对 Bolt 事务语义有一些具体的影响，如以下各节所述。
只读 Bolt 交易查询
处理只读查询的方法有多种，具有不同的事务模型和隔离级别，如下所示：
隐式只读交易查询
以下是只读隐式事务的示例：
public void executeReadImplicitTransaction() { // end point final String END_POINT = "(End Point URL)"; // read query final String READ_QUERY = "MATCH (n) RETURN n limit 10"; // create the driver final Driver driver = GraphDatabase.driver(END_POINT, AuthTokens.none(), Config.builder().withEncryption() .withTrustStrategy(TrustStrategy.trustSystemCertificates()) .build()); // create the session config SessionConfig sessionConfig = SessionConfig.builder() .withFetchSize(1000) .withDefaultAccessMode(AccessMode.READ) .build(); // run the query as access mode read driver.session(sessionConfig).readTransaction(new TransactionWork<String>() { final StringBuilder resultCollector = new StringBuilder(); @Override public String execute(final Transaction tx) { // execute the query Result queryResult = tx.run(READ_QUERY); // Read the result for (Record record : queryResult.list()) { for (String key : record.keys()) { resultCollector.append(key) .append(":") .append(record.get(key).asNode().toString()); } } return resultCollector.toString(); } } ); // close the driver. driver.close(); }
由于只读副本只接受只读查询，因此无论会话配置中设置的访问模式如何，针对只读副本的所有查询都将作为只读隐式事务执行。Neptune 将读隐式交易评估为只读查询下SNAPSHOT隔离语义。
在失败的情况下，默认情况下会重试读隐式事务。
自动提交只读事务查询
以下是只读自动提交事务的示例：
public void executeAutoCommitTransaction() { // end point final String END_POINT = "(End Point URL)"; // read query final String READ_QUERY = "MATCH (n) RETURN n limit 10"; // Create the session config. final SessionConfig sessionConfig = SessionConfig .builder() .withFetchSize(1000) .withDefaultAccessMode(AccessMode.READ) .build(); // create the driver final Driver driver = GraphDatabase.driver(END_POINT, AuthTokens.none(), Config.builder() .withEncryption() .withTrustStrategy(TrustStrategy.trustSystemCertificates()) .build()); // result collector final StringBuilder resultCollector = new StringBuilder(); // create a session final Session session = driver.session(sessionConfig); // run the query final Result queryResult = session.run(READ_QUERY); for (final Record record : queryResult.list()) { for (String key : record.keys()) { resultCollector.append(key) .append(":") .append(record.get(key).asNode().toString()); } } // close the session session.close(); // close the driver driver.close(); }
如果访问模式设置为READ在会话配置中，Neptune 将自动提交事务查询评估为只读查询下SNAPSHOT隔离语义。请注意，只读副本只接受只读查询。
如果不传入会话配置，则默认情况下，自动提交查询将使用变异查询隔离进行处理，因此必须传入将访问模式明确设置为的会话配置READ.
在失败的情况下，不会重新尝试只读自动提交查询。
显式只读交易查询
以下是显式只读事务的示例：
public void executeReadExplicitTransaction() { // end point final String END_POINT = "(End Point URL)"; // read query final String READ_QUERY = "MATCH (n) RETURN n limit 10"; // Create the session config. final SessionConfig sessionConfig = SessionConfig .builder() .withFetchSize(1000) .withDefaultAccessMode(AccessMode.READ) .build(); // create the driver final Driver driver = GraphDatabase.driver(END_POINT, AuthTokens.none(), Config.builder() .withEncryption() .withTrustStrategy(TrustStrategy.trustSystemCertificates()) .build()); // result collector final StringBuilder resultCollector = new StringBuilder(); // create a session final Session session = driver.session(sessionConfig); // begin transaction final Transaction tx = session.beginTransaction(); // run the query on transaction final List<Record> list = tx.run(READ_QUERY).list(); // read the result for (final Record record : list) { for (String key : record.keys()) { resultCollector .append(key) .append(":") .append(record.get(key).asNode().toString()); } } // commit the transaction and for rollback we can use beginTransaction.rollback(); tx.commit(); // close the driver driver.close(); }
如果访问模式设置为READ在会话配置中，Neptune 将显式只读事务评估为只读查询下SNAPSHOT隔离语义。请注意，只读副本只接受只读查询。
如果不传入会话配置，则默认情况下会使用变异查询隔离来处理显式只读事务，因此必须传入将访问模式明确设置为的会话配置READ.
在失败的情况下，默认情况下将重试只读显式查询。
突变 Bolt 交易查询
与只读查询一样，可以通过多种方式处理变异查询，具有不同的事务模型和隔离级别，如下所示：
隐式变异交易查询
下面是隐式突变交易示例：
public void executeWriteImplicitTransaction() { // end point final String END_POINT = "(End Point URL)"; // create node with label as label and properties. final String WRITE_QUERY = "CREATE (n:label {name : 'foo'})"; // Read the vertex created with label as label. final String READ_QUERY = "MATCH (n:label) RETURN n"; // create the driver final Driver driver = GraphDatabase.driver(END_POINT, AuthTokens.none(), Config.builder() .withEncryption() .withTrustStrategy(TrustStrategy.trustSystemCertificates()) .build()); // create the session config SessionConfig sessionConfig = SessionConfig .builder() .withFetchSize(1000) .withDefaultAccessMode(AccessMode.WRITE) .build(); final StringBuilder resultCollector = new StringBuilder(); // run the query as access mode write driver.session(sessionConfig).writeTransaction(new TransactionWork<String>() { @Override public String execute(final Transaction tx) { // execute the write query and consume the result. tx.run(WRITE_QUERY).consume(); // read the vertex written in the same transaction final List<Record> list = tx.run(READ_QUERY).list(); // read the result for (final Record record : list) { for (String key : record.keys()) { resultCollector .append(key) .append(":") .append(record.get(key).asNode().toString()); } } return resultCollector.toString(); } }); // at the end, the transaction is automatically committed. // close the driver. driver.close(); }
在变异查询中进行的读取将在下执行READ COMMITTED与通常的保证隔离Neptune 突变交易.
无论您是否具体传入会话配置，事务始终被视为写入事务。
有关冲突，请参阅使用锁定等待超时解决冲突.
自动提交变异事务查询
变异自动提交查询继承与变异隐式事务相同的行为。
如果没有传入会话配置，默认情况下，该事务将被视为写入事务。
在失败的情况下，不会自动重试变异自动提交查询。
显式变异交易查询
下面是一个显式突变交易示例：
public void executeWriteExplicitTransaction() { // end point final String END_POINT = "(End Point URL)"; // create node with label as label and properties. final String WRITE_QUERY = "CREATE (n:label {name : 'foo'})"; // Read the vertex created with label as label. final String READ_QUERY = "MATCH (n:label) RETURN n"; // create the driver final Driver driver = GraphDatabase.driver(END_POINT, AuthTokens.none(), Config.builder() .withEncryption() .withTrustStrategy(TrustStrategy.trustSystemCertificates()) .build()); // create the session config SessionConfig sessionConfig = SessionConfig .builder() .withFetchSize(1000) .withDefaultAccessMode(AccessMode.WRITE) .build(); final StringBuilder resultCollector = new StringBuilder(); final Session session = driver.session(sessionConfig); // run the query as access mode write final Transaction tx = driver.session(sessionConfig).beginTransaction(); // execute the write query and consume the result. tx.run(WRITE_QUERY).consume(); // read the result from the previous write query in a same transaction. final List<Record> list = tx.run(READ_QUERY).list(); // read the result for (final Record record : list) { for (String key : record.keys()) { resultCollector .append(key) .append(":") .append(record.get(key).asNode().toString()); } } // commit the transaction and for rollback we can use tx.rollback(); tx.commit(); // close the session session.close(); // close the driver. driver.close(); }
显式变异查询继承与隐式变异事务相同的行为。
如果没有传入会话配置，默认情况下，该事务将被视为写入事务。
有关冲突，请参阅使用锁定等待超时解决冲突.