开源OLAP引擎（基于sparkhivethriftserver源码修改）对外提供jdbc接口流程解读

入口demo

public static void main(String[] args) throws ClassNotFoundException, SQLException {

        Class.forName("org.apache.hive.jdbc.HiveDriver");

//        Connection conn = DriverManager.getConnection("jdbc:hive2://hostname:10007","admin","12345+");
        Connection conn = DriverManager.getConnection("jdbc:zk://hostname:2181/;tenant=admin", "carm", "12345+");


        PreparedStatement pstat = conn.prepareStatement("select   * from tableGroupA where  InfoIndex    rlike  'abcxyz\\\\'   limit   100");
//        PreparedStatement pstat = conn.prepareStatement("select * from default.testschema071902 limit 10");
        pstat.setQueryTimeout(666);
        pstat.execute();
        ResultSet rs = pstat.executeQuery();
        while (rs.next()) {

            String name = rs.getString("rowKey");
            System.out.println(name);
        }

    }

跟一般数据库的jdbc使用一样，一开始通过Class.forname加载加载数据库驱动包，这个这个地方有不明的地方，可以参考https://blog.youkuaiyun.com/qq_29924227/article/details/81042958这个

然后就是通过DriverManager.getConnection（原理可以参https://blog.youkuaiyun.com/yumenshizhongjingjie/article/details/81036357，写的行详细）,传入jdbc的连接和用户名密码。

接下来就进入org.apache.hive.jdbc.HiveDriver#connect

public Connection connect(String url, Properties info) throws SQLException {
        if (acceptsURL(url))
            return new HiveConnection(url, info);
        return null;
    }

acceptsURL(url)中对传入进来的url做了个正则表达是匹配，只支持zk和hive2的两种方式进行连接，匹配则继续，new一个HiveConnection

HiveConnection中初始化了一个client，分两种情况，分别是

if (isEmbeddedMode) {
            EmbeddedThriftBinaryCLIService embeddedClient = new EmbeddedThriftBinaryCLIService();
            embeddedClient.init(new HiveConf());
            client = embeddedClient;
        } else {
            // extract user/password from JDBC connection properties if its not supplied in the
            // connection URL
            if (info.containsKey(JdbcConnectionParams.AUTH_USER)) {
                sessConfMap.put(JdbcConnectionParams.AUTH_USER, info.getProperty(JdbcConnectionParams.AUTH_USER));
                if (info.containsKey(JdbcConnectionParams.AUTH_PASSWD)) {
                    sessConfMap.put(JdbcConnectionParams.AUTH_PASSWD, info.getProperty(JdbcConnectionParams.AUTH_PASSWD));
                }
            }
            if (info.containsKey(JdbcConnectionParams.AUTH_TYPE)) {
                sessConfMap.put(JdbcConnectionParams.AUTH_TYPE, info.getProperty(JdbcConnectionParams.AUTH_TYPE));
            }
            // open the client transport
            openTransport();
            // set up the client
            client = new TCLIService.Client(new TBinaryProtocol(transport));
        }

然后通过client创建了一个session

TOpenSessionResp openResp = client.OpenSession(openReq);后面详细的代码就先不看了

我们回到一开始的代码，

PreparedStatement pstat = conn.prepareStatement("select   * from tableGroupA where  InfoIndex    rlike  'abcxyz\\\\'   limit   100");

这里调用了HiveConnection.prepareStatement(sql)方法，其实最终调用的是下面的这个方法

public HivePreparedStatement(HiveConnection connection, TCLIService.Iface client,
      TSessionHandle sessHandle, String sql) {
    super(connection, client, sessHandle);
    this.sql = sql;
  }

然后执行

pstat.execute();

这里最终执行的是

public boolean execute(String sql) throws SQLException {
    checkConnection("execute");

    closeClientOperation();
    initFlags();

    TExecuteStatementReq execReq = new TExecuteStatementReq(sessHandle, sql);
    /**
     * Run asynchronously whenever possible
     * Currently only a SQLOperation can be run asynchronously,
     * in a background operation thread
     * Compilation is synchronous and execution is asynchronous
     */
    execReq.setRunAsync(true);
    sessConf.put(Utils.QUERY_TIME_OUT,String.valueOf(timeoutInSecond));
    execReq.setConfOverlay(sessConf);

    transportLock.lock();
    try {
//这里调用的是org.apache.hive.service.cli.thrift.ThriftCLIService#ExecuteStatement这个方法
      TExecuteStatementResp execResp = client.ExecuteStatement(execReq);
      Utils.verifySuccessWithInfo(execResp.getStatus());
      stmtHandle = execResp.getOperationHandle();
      isExecuteStatementFailed = false;
    } catch (SQLException eS) {
      isExecuteStatementFailed = true;
      throw eS;
    } catch (Exception ex) {
      isExecuteStatementFailed = true;
      throw new SQLException(ex.toString(), "08S01", ex);
    } finally {
      transportLock.unlock();
    }

    TGetOperationStatusReq statusReq = new TGetOperationStatusReq(stmtHandle);
    boolean operationComplete = false;
    TGetOperationStatusResp statusResp;

    // Poll on the operation status, till the operation is complete
    while (!operationComplete) {
      try {
        /**
         * For an async SQLOperation, GetOperationStatus will use the long polling approach
         * It will essentially return after the HIVE_SERVER2_LONG_POLLING_TIMEOUT (a server config) expires
         */
        transportLock.lock();
        try {
          statusResp = client.GetOperationStatus(statusReq);
        } finally {
          transportLock.unlock();
        }
        Utils.verifySuccessWithInfo(statusResp.getStatus());
        if (statusResp.isSetOperationState()) {
          switch (statusResp.getOperationState()) {
          case CLOSED_STATE:
          case FINISHED_STATE:
            operationComplete = true;
            break;
          case CANCELED_STATE:
            // 01000 -> warning
            throw new SQLException("Query was cancelled", "01000");
          case ERROR_STATE:
            // Get the error details from the underlying exception
            throw new SQLException(statusResp.getErrorMessage(),
                statusResp.getSqlState(), statusResp.getErrorCode());
          case UKNOWN_STATE:
            throw new SQLException("Unknown query", "HY000");
          case INITIALIZED_STATE:
          case PENDING_STATE:
          case RUNNING_STATE:
            break;
          }
        }
      } catch (SQLException e) {
        isLogBeingGenerated = false;
        throw e;
      } catch (Exception e) {
        isLogBeingGenerated = false;
        throw new SQLException(e.toString(), "08S01", e);
      }
    }
    isLogBeingGenerated = false;

    // The query should be completed by now
    if (!stmtHandle.isHasResultSet()) {
      return false;
    }
    resultSet =  new HiveQueryResultSet.Builder(this).setClient(client).setSessionHandle(sessHandle)
        .setStmtHandle(stmtHandle).setMaxRows(maxRows).setFetchSize(fetchSize)
        .setScrollable(isScrollableResultset).setTransportLock(transportLock)
        .build();
    return true;
  }

然后进入方法，org.apache.hive.service.cli.thrift.ThriftCLIService#ExecuteStatement

public TExecuteStatementResp ExecuteStatement(TExecuteStatementReq req) throws TException {
    TExecuteStatementResp resp = new TExecuteStatementResp();
    try {
      SessionHandle sessionHandle = new SessionHandle(req.getSessionHandle());
      String statement = req.getStatement();
      Map<String, String> confOverlay = req.getConfOverlay();
      Boolean runAsync = req.isRunAsync();
      OperationHandle operationHandle = runAsync ?
          cliService.executeStatementAsync(sessionHandle, statement, confOverlay)
          : cliService.executeStatement(sessionHandle, statement, confOverlay);
          resp.setOperationHandle(operationHandle.toTOperationHandle());
          resp.setStatus(OK_STATUS);
    } catch (Exception e) {
      LOG.warn("Error executing statement: ", e);
      resp.setStatus(HiveSQLException.toTStatus(e));
    }
    return resp;
  }

至此，后续的逻辑已经可以和我上一篇的博客https://blog.youkuaiyun.com/riluomati/article/details/108349547能串起来了

代码流程看的比较粗枝大叶，其实想看下整个流程的走向，单纯的只是做个记录，如果有错误的地方请轻喷哈，也深深体会到，代码流程这玩意，用语言流畅的表述出来，是个很困难的事情啊，先到这吧……