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，每个表提供有关 NDB 集群节点状态、资源使用情况和操作的不同类型的数据。您可以在接下来的几节中找到有关这些表的更详细的信息。

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

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     |
+----------------------------------+----------+--------------------+---------+---------+
46 rows in set (0.00 sec)

您还可以通过检查 SHOW ENGINES 的输出结果来执行此操作，以查找在 Engine 列中包含 ndbinfo，并在 Support 列中包含 YES 的行，如下所示（强调的文本）

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，那么您可以使用 mysql 或其他 MySQL 客户端中的 SQL 语句访问 ndbinfo。例如，您可以看到 SHOW DATABASES 输出结果中列出的 ndbinfo，如下所示（强调的文本）

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 选项启动，则 ndbinfo 不可使用，并且不会在 SHOW DATABASES 中显示。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），则 ndbinfo 及其表仍然可见，但尝试访问任何表（除了 blocks 或 config_params）都会失败，并出现 Got error 157 'Connection to NDB failed' from NDBINFO 错误。

除了 blocks 表和 config_params 表之外，我们所称的 ndbinfo “表” 实际上是从内部 NDB 表中生成的视图，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，但这通常没有必要。

所有 ndbinfo 表都是只读的，并在查询时按需生成。由于许多表是由数据节点并行生成的，而另一些表特定于给定的 SQL 节点，因此无法保证它们提供一致的快照。

此外，不支持对 ndbinfo 表进行联接下推；因此，联接大型 ndbinfo 表可能需要将大量数据传输到请求 API 节点，即使查询使用了 WHERE 子句。

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，就像其他任何数据库一样，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 的输出结果中，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，例如使用 memoryusage 表的以下两个 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（就像 ndbinfo 数据库本身的名称一样）。这些标识符使用小写。尝试使用错误的大小写会导致错误，例如

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 完全忽略了 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 FILES 表（包含有关用于 NDB 集群磁盘数据存储的文件的信息）和 ndb_transid_mysql_connection_map 表（显示事务、事务协调器和 NDB 集群 API 节点之间的关系）。有关更多信息，请参阅表描述或 第 25.6.18 节“NDB 集群的 INFORMATION_SCHEMA 表”。