ndbinfo 是一个包含 NDB 集群特定信息的数据库。

该数据库包含多个表，每个表提供了 NDB 集群节点状态、资源使用情况和操作的不同类型的数据。你可以在接下来的几节中找到每个表的详细信息。

ndbinfo 随 NDB 集群支持一起包含在 MySQL 服务器中；不需要特殊的编译或配置步骤；表格是在 MySQL 服务器连接到集群时创建的。你可以使用 SHOW PLUGINS 来验证 ndbinfo 支持是否活动在给定的 MySQL 服务器实例中；如果 ndbinfo 支持启用，你应该看到一个包含 ndbinfo 的行在 Name 列中和 ACTIVE 在 Status 列中，如下所示（强调文本）：

mysql> SHOW PLUGINS;
+----------------------------------+--------+--------------------+---------+---------+
| Name                             | Status | Type               | Library | License |
+----------------------------------+--------+--------------------+---------+---------+
| binlog                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| mysql_native_password            | ACTIVE | AUTHENTICATION     | 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     |
+----------------------------------+--------+--------------------+---------+---------+
47 rows in set (0.00 sec)

你也可以通过检查 SHOW ENGINES 的输出，查找包含 ndbinfo 的行在 Engine 列中和 YES 在 Support 列中，如下所示（强调文本）：

mysql> SHOW ENGINES\G
*************************** 1. row ***************************
      Engine: ndbcluster
     Support: YES
     Comment: Clustered, fault-tolerant tables
Transactions: YES
          XA: NO
  Savepoints: NO
*************************** 2. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 4. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM 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: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: ndbinfo
     Support: YES
     Comment: NDB Cluster system information storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 10. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
10 rows in set (0.00 sec)

如果 ndbinfo 支持启用，那么你可以使用 SQL 语句在 mysql 或其他 MySQL 客户端中访问 ndbinfo。例如，你可以在 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 进程没有使用 --ndbcluster 选项，ndbinfo 不可用且不会被 SHOW DATABASES 显示。如果 mysqld 以前连接到 NDB 集群，但集群变得不可用（由于事件如集群关闭、网络连接中断等），ndbinfo 和其表格仍然可见，但尝试访问任何表格（除了 blocks 或 config_params）将失败，显示 Got error 157 'Connection to NDB failed' from NDBINFO。

除了 blocks 和 config_params 表格外，我们所说的 ndbinfo “表格” 实际上是从内部 NDB 表格生成的视图，不通常对 MySQL 服务器可见。你可以通过设置 ndbinfo_show_hidden 系统变量为 ON（或 1）来使这些表格可见，但这通常不是必要的。

所有 ndbinfo 表格都是只读的，并且是在查询时生成的。由于许多表格是由数据节点并行生成的，而其他表格特定于给定的 SQL 节点，因此它们不能保证提供一致的快照。

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

ndbinfo 表格不包括在查询缓存中。（Bug #59831）

你可以使用 USE 语句选择 ndbinfo 数据库，然后发出 SHOW TABLES 语句来获取表格列表，就像对其他数据库一样，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；然而，在 SHOW ENGINES 和 SHOW PLUGINS 的输出中仍然会出现一个 ndbinfo 条目，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 SELECT 语句的查询，使用 memoryusage 表，也是可能的：

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 表和列名是区分大小写的（与 ndbinfo 数据库本身的名称一样）。这些标识符都是小写的。尝试使用错误的字母大小写将导致错误，如下所示：

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，并将其排除在任何输出之外。这甚至适用于使用 --databases 或 --all-databases 选项。

NDB Cluster 还维护了 INFORMATION_SCHEMA 信息数据库中的表，包括 FILES 表，该表包含 NDB Cluster 磁盘数据存储所使用的文件信息，以及 ndb_transid_mysql_connection_map 表，该表显示了事务、事务协调器和 NDB Cluster API 节点之间的关系。有关更多信息，请参阅表的描述或 第 25.6.18 节，“INFORMATION_SCHEMA 表 for NDB Cluster”。