Transaction support

[zhicwu]

Server

• Transaction ID: Tuple(snapshot_version UInt64, local_txid_counter UInt64, host_id UUID)
• functions: transactionID(), transactionLatestSnapshot(), transactionOldestSnapshot()
• settings: throw_on_unsupported_query_inside_transaction, wait_changes_become_visible_after_commit_mode, implicit_transaction
• statements: begin transaction, commit, rollback, set transaction snapshot <snapshot id>, kill transaction where tid=<transaction id>

Java Client

• [x] new client option transaction_timeout, defaults to session_timeout
• [x] add ClickHouseTransaction with methods for begin/commit/rollback transaction and snapshot
• [x] add ClickHouseRequestManager for generating query id and session id as well as transaction creation
• [x] enhance ClickHouseRequest by adding methods getTransaction and setTransaction - multiple requests can take part in one transaction
• [x] throw ClickHouseTransactionException for Code: 649. DB::Exception: Cannot execute query because current transaction failed. Expecting ROLLBACK statement. (INVALID_TRANSACTION) - server will rollback automatically but still needs client to explicitly to acknowledge that by issue rollback(using connection.rollback())
• [x] always create new session when begin transaction and enforce session_check until transaction completed
• [x] consider transaction in retry and failover(avoid node switching)

JDBC Driver

• [x] new JDBC option transactionSupport (defaults to false)
• [x] use implicit_transaction in auto commit mode, fallback to TCL when it's not supported
• [x] replace FakeTransaction when transaction support is enabled
• [x] change default transaction isolation level to repeatable-read(why?)
• [ ] parse TCL to maintain transaction consistency between server and client in 0.3.3?
• [ ] update SIT base classes in 0.3.3 to use docker-compose instead of standalone container and then enable tests for HA and TX in CI

[zhicwu]

Usage(as of 0.3.2-patch11):

• Java Client

  ClickHouseNode server = ClickHouseNode.of("http://localhost:48011/system?transactionSupport");
  try (ClickHouseClient client = ClickHouseClient.newInstance(server.getProtocol())) {
      // implicit transaction
      try (ClickHouseResponse response = client.connect(server)
          .format(ClickHouseFormat.RowBinaryWithNamesAndTypes)
          .query("select 1")
          // blocking call to create and start a new transaction, issue query, and then commit/rollback automatically
          .executeWithinTransaction()) {
          ...
      }
  
      ClickHouseRequest<?> reqWithManualTx = client.connect(server)
          .format(ClickHouseFormat.RowBinaryWithNamesAndTypes)
          .transaction() // create a new transaction and call its begin() method right now
          .query("select 1");
      try (ClickHouseResponse response = reqWithManualTx.executeAndWait()) {
          ...
      }
      reqWithManualTx.getTransaction().commit(); // commit the transaction right away
  }
  

• JDBC Driver

  // auto-commit
  try (Connection conn = DriverManager.getConnection("jdbc:ch:http://localhost:48011/system?transactionSupport");
      Statement stmt = conn.createStatement()) {
      stmt.executeQuery("select 1");
      ...
  }
  
  // manual
  try (Connection conn = DriverManager.getConnection("jdbc:ch:http://localhost:48011/system?!autoCommit&transactionSupport");
      Statement stmt = conn.createStatement()) {
      stmt.executeQuery("select 1");
      conn.commit();
  }
  

Performance penalty for transaction support is acceptable(on client side):

[hantaoliulinux]

Hello, can you provide an example of transactional data insertion using PreparedStatement about JDBC Driver?

[zhicwu]

Hello, can you provide an example of transactional data insertion using PreparedStatement about JDBC Driver?

Hi @hantaoliulinux, did you run into any issue using above examples? The usage is same for Statement and PreparedStatement. FYI, transaction won't start in 0.4.0 and 0.4.1, please use v0.3.2-patch11(or wait for 0.4.2) for transaction support.