ndbinfo 是一個包含 NDB Cluster 特定資訊的資料庫。

此資料庫包含許多表格，每個表格提供關於 NDB Cluster 節點狀態、資源使用和操作的不同類型資料。您可以在接下來的幾個章節中找到關於每個表格的更多詳細資訊。

ndbinfo 包含在 MySQL Server 的 NDB Cluster 支援中；不需要特殊的編譯或組態步驟；這些表格會在 MySQL Server 連接到叢集時建立。您可以使用 SHOW PLUGINS 來驗證給定 MySQL Server 實例中的 ndbinfo 支援是否為作用中；如果 ndbinfo 支援已啟用，您應該會在 Name 欄位中看到包含 ndbinfo 的列，並且在 Status 欄位中看到 ACTIVE，如下所示（強調文字）

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)

您也可以藉由檢查 SHOW ENGINES 的輸出中，是否有在 Engine 欄位包含 ndbinfo 且在 Support 欄位包含 YES 的行來達成，如下所示（強調文字）

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 ndbinfo 支援已啟用，則您可以在 mysql 或其他 MySQL 用戶端中使用 SQL 陳述式存取 ndbinfo。例如，您可以在 SHOW DATABASES 的輸出中看到列出的 ndbinfo，如下所示（強調文字）

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

如果 mysqld 程序未以 --ndbcluster 選項啟動，則 ndbinfo 不會可用，且不會由 SHOW DATABASES 顯示。如果 mysqld 先前已連線至 NDB Cluster，但叢集變為不可用（由於叢集關閉、網路連線遺失等等事件），ndbinfo 及其表格仍然可見，但是嘗試存取任何表格（除了 blocks 或 config_params 之外）會失敗，並顯示 Got error 157 'Connection to NDB failed' from NDBINFO 的錯誤訊息。

除了 blocks 和 config_params 表格之外，我們所謂的 ndbinfo「表格」實際上是從內部 NDB 表格產生的檢視，通常對 MySQL Server 不可見。您可以透過將 ndbinfo_show_hidden 系統變數設定為 ON（或 1）來使這些表格可見，但通常不需要這樣做。

所有 ndbinfo 表格都是唯讀的，並且在查詢時按需產生。由於它們中的許多表格是由資料節點平行產生，而其他的則是特定於給定 SQL 節點的，因此它們不保證提供一致的快照。

此外，在 ndbinfo 表格上不支援下推聯結；因此，即使查詢使用了 WHERE 子句，聯結大型 ndbinfo 表格也可能需要將大量資料傳輸到請求的 API 節點。

ndbinfo 表格不包含在查詢快取中。（錯誤 #59831）

您可以使用 USE 陳述式選取 ndbinfo 資料庫，然後發出 SHOW TABLES 陳述式來取得表格清單，就像任何其他資料庫一樣，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 表格都使用 NDB 儲存引擎；但是，ndbinfo 條目仍然會如先前所述出現在 SHOW ENGINES 和 SHOW PLUGINS 的輸出中。

您可以針對這些表格執行 SELECT 陳述式，就像您通常預期的一樣

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)

更複雜的查詢是可能的，例如以下兩個使用 memoryusage 表格的 SELECT 陳述式

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 表格和欄位名稱是區分大小寫的（ndbinfo 資料庫本身的名稱也是如此）。這些識別碼都是小寫。嘗試使用錯誤的大小寫會導致錯誤，如本範例所示

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 會完全忽略 ndbinfo 資料庫，並將其排除在任何輸出之外。即使使用 --databases 或 --all-databases 選項，情況也是如此。

NDB Cluster 也會在 INFORMATION_SCHEMA 資訊資料庫中維護表格，包括 FILES 表格，其中包含有關用於 NDB Cluster 磁碟資料儲存的檔案資訊，以及 ndb_transid_mysql_connection_map 表格，顯示交易、交易協調器和 NDB Cluster API 節點之間的關係。如需更多資訊，請參閱表格的說明或 第 25.6.18 節，「NDB Cluster 的 INFORMATION_SCHEMA 表格」。