ndbinfo 是一个包含 NDB 集群特定信息的数据库。

此数据库包含许多表，每个表都提供有关 NDB 集群节点状态、资源使用情况和操作的不同类型数据。您可以在接下来的几节中找到有关每个表的更详细信息。

ndbinfo 包含在 MySQL 服务器的 NDB 集群支持中；不需要特殊的编译或配置步骤；这些表由 MySQL 服务器在连接到集群时创建。您可以使用 SHOW PLUGINS 验证给定 MySQL 服务器实例中是否激活了 ndbinfo 支持；如果启用了 ndbinfo 支持，您应该会在 Name 列中看到包含 ndbinfo 的行，并在 Status 列中看到 ACTIVE，如下所示（强调文本）

mysql> SHOW PLUGINS;
+----------------------------------+--------+--------------------+---------+---------+
| Name                             | Status | Type               | Library | License |
+----------------------------------+--------+--------------------+---------+---------+
| binlog                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| sha256_password                  | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| caching_sha2_password            | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| sha2_cache_cleaner               | ACTIVE | AUDIT              | NULL    | GPL     |
| daemon_keyring_proxy_plugin      | ACTIVE | DAEMON             | NULL    | GPL     |
| CSV                              | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MEMORY                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| InnoDB                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| INNODB_TRX                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_RESET                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM                    | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM_RESET              | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_PER_INDEX             | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_PER_INDEX_RESET       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_PAGE               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_PAGE_LRU           | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_BUFFER_POOL_STATS         | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TEMP_TABLE_INFO           | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_METRICS                   | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_DEFAULT_STOPWORD       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_DELETED                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_BEING_DELETED          | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_CONFIG                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_INDEX_CACHE            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_FT_INDEX_TABLE            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TABLES                    | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TABLESTATS                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_INDEXES                   | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_TABLESPACES               | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_COLUMNS                   | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_VIRTUAL                   | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CACHED_INDEXES            | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_SESSION_TEMP_TABLESPACES  | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| MyISAM                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MRG_MYISAM                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| PERFORMANCE_SCHEMA               | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| TempTable                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ARCHIVE                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| BLACKHOLE                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbcluster                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbinfo                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndb_transid_mysql_connection_map | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| ngram                            | ACTIVE | FTPARSER           | NULL    | GPL     |
| mysqlx_cache_cleaner             | ACTIVE | AUDIT              | NULL    | GPL     |
| mysqlx                           | ACTIVE | DAEMON             | NULL    | GPL     |
| mysql_native_password            | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
+----------------------------------+--------+--------------------+---------+---------+
47 rows in set (0.00 sec)

您还可以通过检查 SHOW ENGINES 的输出中是否有一行包含 Engine 列中的 ndbinfo 和 Support 列中的 YES 来执行此操作，如下所示（强调文本）

mysql> SHOW ENGINES\G
*************************** 1. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 3. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: ndbinfo
     Support: YES
     Comment: MySQL Cluster system information storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 6. row ***************************
      Engine: MRG_MYISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 10. row ***************************
      Engine: ndbcluster
     Support: YES
     Comment: Clustered, fault-tolerant tables
Transactions: YES
          XA: NO
  Savepoints: NO
10 rows in set (0.01 sec)

如果启用了 ndbinfo 支持，则可以使用 mysql 或其他 MySQL 客户端中的 SQL 语句访问 ndbinfo。例如，您可以在 SHOW DATABASES 的输出中看到 ndbinfo，如下所示（强调文本）

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| ndbinfo            |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.04 sec)

如果 mysqld 进程不是使用 --ndbcluster 选项启动的，则 ndbinfo 不可用，并且不会由 SHOW DATABASES 显示。如果 mysqld 以前连接到 NDB 集群，但集群变得不可用（由于集群关闭、网络连接丢失等事件），ndbinfo 及其表仍然可见，但尝试访问任何表（blocks 或 config_params 除外）将失败，并显示 Got error 157 'Connection to NDB failed' from NDBINFO。

除了 blocks 和 config_params 表之外，我们所说的 ndbinfo “表” 实际上是从内部 NDB 表生成的视图，这些表通常对 MySQL 服务器不可见。您可以通过将 ndbinfo_show_hidden 系统变量设置为 ON（或 1）来使这些表可见，但这通常不是必需的。

所有 ndbinfo 表都是只读的，并在查询时按需生成。因为其中许多表是由数据节点并行生成的，而其他表特定于给定的 SQL 节点，所以不能保证它们提供一致的快照。

此外，ndbinfo 表不支持下推连接；因此，即使查询使用了 WHERE 子句，连接大型 ndbinfo 表也可能需要将大量数据传输到请求 API 节点。

ndbinfo 表不包含在查询缓存中。（错误 #59831）

您可以使用 USE 语句选择 ndbinfo 数据库，然后发出 SHOW TABLES 语句以获取表列表，就像任何其他数据库一样，如下所示

mysql> USE ndbinfo;
Database changed

mysql> SHOW TABLES;
+---------------------------------+
| Tables_in_ndbinfo               |
+---------------------------------+
| arbitrator_validity_detail      |
| arbitrator_validity_summary     |
| backup_id                       |
| blobs                           |
| blocks                          |
| certificates                    |
| cluster_locks                   |
| cluster_operations              |
| cluster_transactions            |
| config_nodes                    |
| config_params                   |
| config_values                   |
| counters                        |
| cpudata                         |
| cpudata_1sec                    |
| cpudata_20sec                   |
| cpudata_50ms                    |
| cpuinfo                         |
| cpustat                         |
| cpustat_1sec                    |
| cpustat_20sec                   |
| cpustat_50ms                    |
| dict_obj_info                   |
| dict_obj_tree                   |
| dict_obj_types                  |
| dictionary_columns              |
| dictionary_tables               |
| disk_write_speed_aggregate      |
| disk_write_speed_aggregate_node |
| disk_write_speed_base           |
| diskpagebuffer                  |
| diskstat                        |
| diskstats_1sec                  |
| error_messages                  |
| events                          |
| files                           |
| foreign_keys                    |
| hash_maps                       |
| hwinfo                          |
| index_columns                   |
| index_stats                     |
| locks_per_fragment              |
| logbuffers                      |
| logspaces                       |
| membership                      |
| memory_per_fragment             |
| memoryusage                     |
| nodes                           |
| operations_per_fragment         |
| pgman_time_track_stats          |
| processes                       |
| resources                       |
| restart_info                    |
| server_locks                    |
| server_operations               |
| server_transactions             |
| table_distribution_status       |
| table_fragments                 |
| table_info                      |
| table_replicas                  |
| tc_time_track_stats             |
| threadblocks                    |
| threads                         |
| threadstat                      |
| transporter_details             |
| transporters                    |
+---------------------------------+
66 rows in set (0.00 sec)

所有 ndbinfo 表都使用 NDB 存储引擎；但是，ndbinfo 条目仍然会出现在 SHOW ENGINES 和 SHOW PLUGINS 的输出中，如前所述。

您可以对这些表执行 SELECT 语句，就像您通常期望的那样

mysql> SELECT * FROM memoryusage;
+---------+---------------------+--------+------------+------------+-------------+
| node_id | memory_type         | used   | used_pages | total      | total_pages |
+---------+---------------------+--------+------------+------------+-------------+
|       5 | Data memory         | 425984 |         13 | 2147483648 |       65536 |
|       5 | Long message buffer | 393216 |       1536 |   67108864 |      262144 |
|       6 | Data memory         | 425984 |         13 | 2147483648 |       65536 |
|       6 | Long message buffer | 393216 |       1536 |   67108864 |      262144 |
|       7 | Data memory         | 425984 |         13 | 2147483648 |       65536 |
|       7 | Long message buffer | 393216 |       1536 |   67108864 |      262144 |
|       8 | Data memory         | 425984 |         13 | 2147483648 |       65536 |
|       8 | Long message buffer | 393216 |       1536 |   67108864 |      262144 |
+---------+---------------------+--------+------------+------------+-------------+
8 rows in set (0.09 sec)

更复杂的查询，例如以下两个使用 memoryusage 表的 SELECT 语句，是可能的

mysql> SELECT SUM(used) as 'Data Memory Used, All Nodes'
     >     FROM memoryusage
     >     WHERE memory_type = 'Data memory';
+-----------------------------+
| Data Memory Used, All Nodes |
+-----------------------------+
|                        6460 |
+-----------------------------+
1 row in set (0.09 sec)

mysql> SELECT SUM(used) as 'Long Message Buffer, All Nodes'
     >     FROM memoryusage
     >     WHERE memory_type = 'Long message buffer';
+-------------------------------------+
| Long Message Buffer Used, All Nodes |
+-------------------------------------+
|                             1179648 |
+-------------------------------------+
1 row in set (0.08 sec)

ndbinfo 表和列名区分大小写（ndbinfo 数据库本身的名称也是如此）。这些标识符是小写的。尝试使用错误的大小写会导致错误，如本例所示

mysql> SELECT * FROM nodes;
+---------+--------+---------+-------------+-------------------+
| node_id | uptime | status  | start_phase | config_generation |
+---------+--------+---------+-------------+-------------------+
|       5 |  17707 | STARTED |           0 |                 1 |
|       6 |  17706 | STARTED |           0 |                 1 |
|       7 |  17705 | STARTED |           0 |                 1 |
|       8 |  17704 | STARTED |           0 |                 1 |
+---------+--------+---------+-------------+-------------------+
4 rows in set (0.06 sec)

mysql> SELECT * FROM Nodes;
ERROR 1146 (42S02): Table 'ndbinfo.Nodes' doesn't exist

mysqldump 完全忽略 ndbinfo 数据库，并将其从任何输出中排除。即使使用 --databases 或 --all-databases 选项也是如此。

NDB 集群还在 INFORMATION_SCHEMA 信息数据库中维护表，包括包含有关用于 NDB 集群磁盘数据存储的文件信息的 FILES 表，以及显示事务、事务协调器和 NDB 集群 API 节点之间关系的 ndb_transid_mysql_connection_map 表。有关详细信息，请参阅表的描述或 第 25.6.18 节，“NDB 集群的 INFORMATION_SCHEMA 表”。