Jaybird 3 和 Firebird 交易信息

Question

在之前版本的 jaybird (2.2) 中，我能够对 Firebird 服务器执行服务 API 以获取活动事务标记：OIT、OAT、Next 等

在 3.0 版本中，我找不到正确的操作方法。只有 ISC-constants（如 isc_info_oldest_snapshot）但没有方法。

所以，我看到了一种方法：通过 StatisticsManager 查询数据库 header。但这并不是那么容易，因为它将 return 需要解析的文本：

    StatisticsManager SM = new FBStatisticsManager();  //"PURE_JAVA", "NATIVE", "EMBEDDED"

    SM.setHost("localhost");
    SM.setUser("sysdba");
    SM.setPort(3053);
    SM.setPassword("masterkey");
    SM.setDatabase("c:\Firebird\3.0.2\examples\empbuild\EMPLOYEE.FDB");

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    SM.setLogger(baos);
    SM.getHeaderPage();
    String outputstr2 = new String( baos.toByteArray(), java.nio.charset.StandardCharsets.UTF_8 );

现在我需要解析文本：

Database "C:\FIREBIRD.0.2\EXAMPLES\EMPBUILD\EMPLOYEE.FDB"
Database header page information:
   Flags            0
   Generation        806
   System Change Number    12
   Page size        8192
   ODS version        12.0
   Oldest transaction    520
   Oldest active        521
   Oldest snapshot        521
   Next transaction    521
   Sequence number        0
   Next attachment ID    857
   Implementation        HW=AMD/Intel/x64 little-endian OS=Windows CC=MSVC
   Shadow count        0
   Page buffers        0
   Next header page    0
   Database dialect    3
   Creation date        Apr 15, 2016 17:38:34
   Attributes        

   Variable header data:
   Database backup GUID:    {6F41E937-76D5-4C67-6CAE-F8556AD27BEE}
   Database GUID:    {EE5B2713-7B17-43B0-0CB3-0616B4B8A63D}
   *END*

是否可以获得直接值？

更新：旧版本的代码是：

/** [ActiveCount, OAT, OST, OIT, Next] */
public static int[] getTxInfo( final GDS gds,
                               final String host,
                               final int port,
                               final String databasePath,
                               final String user,
                               final String password ) throws Exception {
    final byte[] queryItems = {
            ISCConstants.isc_info_oldest_transaction,
            ISCConstants.isc_info_oldest_active,
            ISCConstants.isc_info_oldest_snapshot,
            ISCConstants.isc_info_next_transaction,
            ISCConstants.isc_info_active_transactions,
            ISCConstants.isc_info_end
    };
    byte[] response = queryDB(
            gds, host, port, databasePath, user, password,
            queryItems, DEFAULT_BUFFER_SIZE
    );
    int i = 0;
    final int[] result = new int[5];
    while ( response[i] != ISCConstants.isc_info_end ) {
        final byte code = response[i++];
        switch ( code ) {
            case ISCConstants.isc_info_active_transactions: {
                //здесь идет столько блоков isc_info_active_transactions, сколько
                //реально активных транзакций в данный момент
                final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
                i += LENGTH_LEN;
                //final int res = gds.iscVaxInteger( response, i, valueLen );
                i += valueLen;
                result[0]++;
                break;
            }
            case ISCConstants.isc_info_oldest_active: {
                final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
                i += LENGTH_LEN;
                final int res = gds.iscVaxInteger( response, i, valueLen );
                i += valueLen;
                result[1] = res;
                break;
            }
            case ISCConstants.isc_info_oldest_snapshot: {
                final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
                i += LENGTH_LEN;
                final int res = gds.iscVaxInteger( response, i, valueLen );
                i += valueLen;
                result[2] = res;
                break;
            }
            case ISCConstants.isc_info_oldest_transaction: {
                final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
                i += LENGTH_LEN;
                final int res = gds.iscVaxInteger( response, i, valueLen );
                i += valueLen;
                result[3] = res;
                break;
            }
            case ISCConstants.isc_info_next_transaction: {
                final int valueLen = gds.iscVaxInteger( response, i, LENGTH_LEN );
                i += LENGTH_LEN;
                final int res = gds.iscVaxInteger( response, i, valueLen );
                i += valueLen;
                result[4] = res;
                break;
            }
            case ISCConstants.isc_info_truncated: {
                //этот код означает "буфер слишком маленький, дайте больше"
                //обычно это бывает когда слишком много активных транзакций

                //сначала пробуем увеличить буфер
                if ( response.length == DEFAULT_BUFFER_SIZE ) {
                    response = queryDB(
                            gds, host, port, databasePath, user, password,
                            queryItems, 32 * DEFAULT_BUFFER_SIZE
                    );
                    result[0] = 0;//на всякий случай
                    //начинаем разбор заново
                    i = 0;
                } else {
                    //32Кб буфера оказалось тоже недостаточно -- пичалька. Но
                    //делать нечего -- просто обойдемся без числа активных транзакций
                    response = queryDB(
                            gds, host, port, databasePath, user, password,
                            new byte[]{
                                    ISCConstants.isc_info_oldest_transaction,
                                    ISCConstants.isc_info_oldest_active,
                                    ISCConstants.isc_info_oldest_snapshot,
                                    ISCConstants.isc_info_next_transaction,
                                    ISCConstants.isc_info_end
                            }, DEFAULT_BUFFER_SIZE
                    );
                    result[0] = -1;
                    //начинаем разбор заново
                    i = 0;
                }
                break;
            }

            default:
                throw new FBSQLException( "Unrecognized response code: " + code + " (response=" + Arrays.toString( result ) + ")" );
        }
    }
    return result;
}

其中

public static byte[] queryDB( final GDS gds,
                              final String host,
                              final int port,
                              final String databasePath,
                              final String user,    
                              final String password,
                              final byte[] queryItems,
                              final int bufferLength ) throws Exception {
    return doWithDB(
            gds, host, port, databasePath, user, password,
            new DBOperation<byte[]>() {
                public byte[] doWithDB( final GDS gds,
                                        final IscDbHandle db ) throws GDSException {
                    return gds.iscDatabaseInfo(
                            db,
                            queryItems,
                            bufferLength
                    );
                }
            }
    );
}

够了吗？

Answer 1

select * from MON$DATABASE 会查询 "OIT, OAT, Next"

或者您可以通过 select * from MON$TRANSACTIONS

获取更多详细信息

在c:\Program Files\Firebird\Firebird_2_1\doc\README.monitoring_tables.txt

中查看更多内容

MON$DATABASE (connected database)
  - MON$DATABASE_NAME (database pathname or alias)
  - MON$PAGE_SIZE (page size)
  - MON$ODS_MAJOR (major ODS version)
  - MON$ODS_MINOR (minor ODS version)
  - MON$OLDEST_TRANSACTION (OIT number)
  - MON$OLDEST_ACTIVE (OAT number)
  - MON$OLDEST_SNAPSHOT (OST number)
  - MON$NEXT_TRANSACTION (next transaction number)
  - MON$PAGE_BUFFERS (number of pages allocated in the cache)
  - MON$SQL_DIALECT (SQL dialect of the database)
  - MON$SHUTDOWN_MODE (current shutdown mode)
      0: online
      1: multi-user shutdown
      2: single-user shutdown
      3: full shutdown
  - MON$SWEEP_INTERVAL (sweep interval)
  - MON$READ_ONLY (read-only flag)
  - MON$FORCED_WRITES (sync writes flag)
  - MON$RESERVE_SPACE (reserve space flag)
  - MON$CREATION_DATE (creation date/time)
  - MON$PAGES (number of pages allocated on disk)
  - MON$BACKUP_STATE (current physical backup state)
      0: normal
      1: stalled
      2: merge
  - MON$STAT_ID (statistics ID)

MON$TRANSACTIONS (started transactions)
  - MON$TRANSACTION_ID (transaction ID)
  - MON$ATTACHMENT_ID (attachment ID)
  - MON$STATE (transaction state)
      0: idle
      1: active
  - MON$TIMESTAMP (transaction start date/time)
  - MON$TOP_TRANSACTION (top transaction)
  - MON$OLDEST_TRANSACTION (local OIT number)
  - MON$OLDEST_ACTIVE (local OAT number)
  - MON$ISOLATION_MODE (isolation mode)
      0: consistency
      1: concurrency
      2: read committed record version
      3: read committed no record version
  - MON$LOCK_TIMEOUT (lock timeout)
      -1: infinite wait
      0: no wait
      N: timeout N
  - MON$READ_ONLY (read-only flag)
  - MON$AUTO_COMMIT (auto-commit flag)
  - MON$AUTO_UNDO (auto-undo flag)
  - MON$STAT_ID (statistics ID)

注意 1：那些 table 中的某些数据只有在您通过 SYSDBA 或 RDB$ADMIN 或数据库所有者用户连接时才可用。示例：attachments(connections) table 将使其他用户的连接不可见并针对非管理员用户的请求跳过。

注意 2：从监控 table 中读取可能相对较慢，尤其是从 table 包含连接相关（也称为附件相关）信息的读取。缓慢而阻塞。所以不建议经常做阅读监控tables。

Answer 2

我已将功能添加到 Jaybird 3.0.0，请参阅 this commit。

我添加了两种获取此信息的方法：

使用StatisticsManager:

StatisticsManager statsMan = new FBStatisticsManager();
statsMan.setHost("localhost");
statsMan.setDatabase("/path/to/your.fdb");
statsMan.setUser("youruser");
statsMan.setPassword("yourpassword"); 
DatabaseTransactionInfo info = statsMan.getDatabaseTransactionInfo();

使用现有 Connection 获取此信息的便捷方法：

try (Connection connection = dataSource.getConnection()) {
    DatabaseTransactionInfo info = FBStatisticsManager
            .getDatabaseTransactionInfo(connection);
}

唯一的要求是连接实例解包到 FirebirdConnection 接口。

如果您使用的是 Maven，您可以尝试从 Sonatype OSS 快照存储库获取最新的 Jaybird 快照：https://oss.sonatype.org/content/repositories/snapshots（您需要将此快照存储库添加到您的 Maven 配置中）。

<dependency>
    <groupId>org.firebirdsql.jdbc</groupId>
    <artifactId>jaybird-jdk18</artifactId>
    <version>3.0.0-SNAPSHOT</version>
</dependency>

否则您可以使用以下方式下载快照：

对于未来的版本，我会考虑是否可以以更通用的方式公开数据库信息查询工具，这样就不必使用内部 FbDatabase 接口。

Jaybird 3 和 Firebird 交易信息

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