可以使用多种类型的与对象执行的或影响Ndb
对象的动作相关的统计计数器。此类操作包括开始和关闭（或中止）交易；主键和唯一键操作；表、范围和修剪扫描；线程在等待各种操作完成时被阻塞；发送和接收的数据和事件NDBCLUSTER。每当进行 NDB API 调用或将数据发送到数据节点或由数据节点接收数据时，计数器就会在 NDB 内核中递增。
mysqld将这些计数器公开为系统状态变量；它们的值可以在 的输出中读取
SHOW STATUS，或者通过查询
INFORMATION_SCHEMA.SESSION_STATUS或
INFORMATION_SCHEMA.GLOBAL_STATUS
桌子。通过比较操作表的语句前后的值NDB，您可以观察到在 API 级别采取的相应操作，从而观察执行语句的成本。
您可以使用以下
SHOW STATUS语句列出所有这些状态变量：
mysql> SHOW STATUS LIKE 'ndb_api%';
+----------------------------------------------+-------------+
| Variable_name | Value |
+----------------------------------------------+-------------+
| Ndb_api_wait_exec_complete_count | 2 |
| Ndb_api_wait_scan_result_count | 3 |
| Ndb_api_wait_meta_request_count | 101 |
| Ndb_api_wait_nanos_count | 83664697215 |
| Ndb_api_bytes_sent_count | 13608 |
| Ndb_api_bytes_received_count | 142800 |
| Ndb_api_trans_start_count | 2 |
| Ndb_api_trans_commit_count | 1 |
| Ndb_api_trans_abort_count | 0 |
| Ndb_api_trans_close_count | 2 |
| Ndb_api_pk_op_count | 1 |
| Ndb_api_uk_op_count | 0 |
| Ndb_api_table_scan_count | 1 |
| Ndb_api_range_scan_count | 0 |
| Ndb_api_pruned_scan_count | 0 |
| Ndb_api_scan_batch_count | 0 |
| Ndb_api_read_row_count | 1 |
| Ndb_api_trans_local_read_row_count | 1 |
| Ndb_api_adaptive_send_forced_count | 0 |
| Ndb_api_adaptive_send_unforced_count | 3 |
| Ndb_api_adaptive_send_deferred_count | 0 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
| Ndb_api_wait_exec_complete_count_slave | 0 |
| Ndb_api_wait_scan_result_count_slave | 0 |
| Ndb_api_wait_meta_request_count_slave | 0 |
| Ndb_api_wait_nanos_count_slave | 0 |
| Ndb_api_bytes_sent_count_slave | 0 |
| Ndb_api_bytes_received_count_slave | 0 |
| Ndb_api_trans_start_count_slave | 0 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_abort_count_slave | 0 |
| Ndb_api_trans_close_count_slave | 0 |
| Ndb_api_pk_op_count_slave | 0 |
| Ndb_api_uk_op_count_slave | 0 |
| Ndb_api_table_scan_count_slave | 0 |
| Ndb_api_range_scan_count_slave | 0 |
| Ndb_api_pruned_scan_count_slave | 0 |
| Ndb_api_scan_batch_count_slave | 0 |
| Ndb_api_read_row_count_slave | 0 |
| Ndb_api_trans_local_read_row_count_slave | 0 |
| Ndb_api_adaptive_send_forced_count_slave | 0 |
| Ndb_api_adaptive_send_unforced_count_slave | 0 |
| Ndb_api_adaptive_send_deferred_count_slave | 0 |
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_wait_exec_complete_count_session | 0 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 0 |
| Ndb_api_wait_nanos_count_session | 0 |
| Ndb_api_bytes_sent_count_session | 0 |
| Ndb_api_bytes_received_count_session | 0 |
| Ndb_api_trans_start_count_session | 0 |
| Ndb_api_trans_commit_count_session | 0 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 0 |
| Ndb_api_pk_op_count_session | 0 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 0 |
| Ndb_api_trans_local_read_row_count_session | 0 |
| Ndb_api_adaptive_send_forced_count_session | 0 |
| Ndb_api_adaptive_send_unforced_count_session | 0 |
| Ndb_api_adaptive_send_deferred_count_session | 0 |
+----------------------------------------------+-------------+
69 rows in set (0.00 sec)
这些状态变量也可从数据库的
SESSION_STATUS和
GLOBAL_STATUS表中获得
INFORMATION_SCHEMA，如下所示：
mysql> SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
-> WHERE VARIABLE_NAME LIKE 'ndb_api%';
+----------------------------------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+----------------------------------------------+----------------+
| Ndb_api_wait_exec_complete_count | 2 |
| Ndb_api_wait_scan_result_count | 3 |
| Ndb_api_wait_meta_request_count | 101 |
| Ndb_api_wait_nanos_count | 74890499869 |
| Ndb_api_bytes_sent_count | 13608 |
| Ndb_api_bytes_received_count | 142800 |
| Ndb_api_trans_start_count | 2 |
| Ndb_api_trans_commit_count | 1 |
| Ndb_api_trans_abort_count | 0 |
| Ndb_api_trans_close_count | 2 |
| Ndb_api_pk_op_count | 1 |
| Ndb_api_uk_op_count | 0 |
| Ndb_api_table_scan_count | 1 |
| Ndb_api_range_scan_count | 0 |
| Ndb_api_pruned_scan_count | 0 |
| Ndb_api_scan_batch_count | 0 |
| Ndb_api_read_row_count | 1 |
| Ndb_api_trans_local_read_row_count | 1 |
| Ndb_api_adaptive_send_forced_count | 0 |
| Ndb_api_adaptive_send_unforced_count | 3 |
| Ndb_api_adaptive_send_deferred_count | 0 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
| Ndb_api_wait_exec_complete_count_slave | 0 |
| Ndb_api_wait_scan_result_count_slave | 0 |
| Ndb_api_wait_meta_request_count_slave | 0 |
| Ndb_api_wait_nanos_count_slave | 0 |
| Ndb_api_bytes_sent_count_slave | 0 |
| Ndb_api_bytes_received_count_slave | 0 |
| Ndb_api_trans_start_count_slave | 0 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_abort_count_slave | 0 |
| Ndb_api_trans_close_count_slave | 0 |
| Ndb_api_pk_op_count_slave | 0 |
| Ndb_api_uk_op_count_slave | 0 |
| Ndb_api_table_scan_count_slave | 0 |
| Ndb_api_range_scan_count_slave | 0 |
| Ndb_api_pruned_scan_count_slave | 0 |
| Ndb_api_scan_batch_count_slave | 0 |
| Ndb_api_read_row_count_slave | 0 |
| Ndb_api_trans_local_read_row_count_slave | 0 |
| Ndb_api_adaptive_send_forced_count_slave | 0 |
| Ndb_api_adaptive_send_unforced_count_slave | 0 |
| Ndb_api_adaptive_send_deferred_count_slave | 0 |
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_wait_exec_complete_count_session | 0 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 0 |
| Ndb_api_wait_nanos_count_session | 0 |
| Ndb_api_bytes_sent_count_session | 0 |
| Ndb_api_bytes_received_count_session | 0 |
| Ndb_api_trans_start_count_session | 0 |
| Ndb_api_trans_commit_count_session | 0 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 0 |
| Ndb_api_pk_op_count_session | 0 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 0 |
| Ndb_api_trans_local_read_row_count_session | 0 |
| Ndb_api_adaptive_send_forced_count_session | 0 |
| Ndb_api_adaptive_send_unforced_count_session | 0 |
| Ndb_api_adaptive_send_deferred_count_session | 0 |
+----------------------------------------------+----------------+
69 rows in set (0.00 sec)
mysql> SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS
-> WHERE VARIABLE_NAME LIKE 'ndb_api%';
+----------------------------------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+----------------------------------------------+----------------+
| Ndb_api_wait_exec_complete_count | 2 |
| Ndb_api_wait_scan_result_count | 3 |
| Ndb_api_wait_meta_request_count | 101 |
| Ndb_api_wait_nanos_count | 13640285623 |
| Ndb_api_bytes_sent_count | 13608 |
| Ndb_api_bytes_received_count | 142800 |
| Ndb_api_trans_start_count | 2 |
| Ndb_api_trans_commit_count | 1 |
| Ndb_api_trans_abort_count | 0 |
| Ndb_api_trans_close_count | 2 |
| Ndb_api_pk_op_count | 1 |
| Ndb_api_uk_op_count | 0 |
| Ndb_api_table_scan_count | 1 |
| Ndb_api_range_scan_count | 0 |
| Ndb_api_pruned_scan_count | 0 |
| Ndb_api_scan_batch_count | 0 |
| Ndb_api_read_row_count | 1 |
| Ndb_api_trans_local_read_row_count | 1 |
| Ndb_api_adaptive_send_forced_count | 0 |
| Ndb_api_adaptive_send_unforced_count | 3 |
| Ndb_api_adaptive_send_deferred_count | 0 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
| Ndb_api_wait_exec_complete_count_slave | 0 |
| Ndb_api_wait_scan_result_count_slave | 0 |
| Ndb_api_wait_meta_request_count_slave | 0 |
| Ndb_api_wait_nanos_count_slave | 0 |
| Ndb_api_bytes_sent_count_slave | 0 |
| Ndb_api_bytes_received_count_slave | 0 |
| Ndb_api_trans_start_count_slave | 0 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_abort_count_slave | 0 |
| Ndb_api_trans_close_count_slave | 0 |
| Ndb_api_pk_op_count_slave | 0 |
| Ndb_api_uk_op_count_slave | 0 |
| Ndb_api_table_scan_count_slave | 0 |
| Ndb_api_range_scan_count_slave | 0 |
| Ndb_api_pruned_scan_count_slave | 0 |
| Ndb_api_scan_batch_count_slave | 0 |
| Ndb_api_read_row_count_slave | 0 |
| Ndb_api_trans_local_read_row_count_slave | 0 |
| Ndb_api_adaptive_send_forced_count_slave | 0 |
| Ndb_api_adaptive_send_unforced_count_slave | 0 |
| Ndb_api_adaptive_send_deferred_count_slave | 0 |
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_wait_exec_complete_count_session | 0 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 0 |
| Ndb_api_wait_nanos_count_session | 0 |
| Ndb_api_bytes_sent_count_session | 0 |
| Ndb_api_bytes_received_count_session | 0 |
| Ndb_api_trans_start_count_session | 0 |
| Ndb_api_trans_commit_count_session | 0 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 0 |
| Ndb_api_pk_op_count_session | 0 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 0 |
| Ndb_api_trans_local_read_row_count_session | 0 |
| Ndb_api_adaptive_send_forced_count_session | 0 |
| Ndb_api_adaptive_send_unforced_count_session | 0 |
| Ndb_api_adaptive_send_deferred_count_session | 0 |
+----------------------------------------------+----------------+
69 rows in set (0.01 sec)
每个Ndb对象都有自己的计数器。NDB API 应用程序可以读取计数器的值以用于优化或监视。对于同时使用多个Ndb
对象的多线程客户端，还可以Ndb从属于给定
Ndb_cluster_connection.
暴露了四组这样的计数器。一组仅适用于当前会话；其他 3 个是全球性的。尽管事实上它们的值可以作为mysql
客户端中的会话或全局状态变量获得。这意味着指定
SESSIONorGLOBAL关键字SHOW STATUS对为 NDB API 统计状态变量报告的值没有影响，并且这些变量中的每一个的值是相同的，无论该值是从
SESSION_STATUSor
GLOBAL_STATUS表的等效列获得的。
会话计数器（特定于会话）
会话计数器与
Ndb（仅）当前会话使用的对象相关。其他 MySQL 客户端使用此类对象不会影响这些计数。为了尽量减少与标准 MySQL 会话变量的混淆，我们将与这些 NDB API 会话计数器对应的变量称为“
_session变量”，并带有前导下划线。副本计数器（全局）
这组计数器与
Ndb复制 SQL 线程使用的对象相关，如果有的话。如果这个mysqld 不充当副本，或者不使用NDB表，那么所有这些计数都是 0。我们将相关的状态变量称为 “
_slave变量”（带前导下划线）。喷油器计数器（全球）
注入器计数器与
Ndb二进制日志注入器线程用于侦听集群事件的对象有关。即使不写入二进制日志，附加到 NDB Cluster 的mysqld进程也会继续侦听某些事件，例如模式更改。我们将与 NDB API 注入器计数器对应的状态变量称为“
_injector变量”（带有前导下划线）。服务器（全局）计数器（全局）
这组计数器与 该mysqld
Ndb当前使用的所有对象相关。这包括所有 MySQL 客户端应用程序、副本 SQL 线程（如果有）、binlog 注入器和实用程序线程。NDB我们将与这些计数器对应的状态变量称为“全局变量”或 “ mysqld级变量”。
session您可以通过额外过滤子字符串、slave或
injector变量名称（连同公共前缀Ndb_api）
来获取一组特定变量的值
。对于
_session变量，这可以如下所示完成：
mysql> SHOW STATUS LIKE 'ndb_api%session';
+--------------------------------------------+---------+
| Variable_name | Value |
+--------------------------------------------+---------+
| Ndb_api_wait_exec_complete_count_session | 2 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 1 |
| Ndb_api_wait_nanos_count_session | 8144375 |
| Ndb_api_bytes_sent_count_session | 68 |
| Ndb_api_bytes_received_count_session | 84 |
| Ndb_api_trans_start_count_session | 1 |
| Ndb_api_trans_commit_count_session | 1 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 1 |
| Ndb_api_pk_op_count_session | 1 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 1 |
| Ndb_api_trans_local_read_row_count_session | 1 |
+--------------------------------------------+---------+
18 rows in set (0.50 sec)
要获取 NDB API mysqld级状态变量的列表，请过滤以开头
ndb_api和结尾
的变量名称_count，如下所示：
mysql> SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
-> WHERE VARIABLE_NAME LIKE 'ndb_api%count';
+------------------------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+------------------------------------+----------------+
| NDB_API_WAIT_EXEC_COMPLETE_COUNT | 4 |
| NDB_API_WAIT_SCAN_RESULT_COUNT | 3 |
| NDB_API_WAIT_META_REQUEST_COUNT | 28 |
| NDB_API_WAIT_NANOS_COUNT | 53756398 |
| NDB_API_BYTES_SENT_COUNT | 1060 |
| NDB_API_BYTES_RECEIVED_COUNT | 9724 |
| NDB_API_TRANS_START_COUNT | 3 |
| NDB_API_TRANS_COMMIT_COUNT | 2 |
| NDB_API_TRANS_ABORT_COUNT | 0 |
| NDB_API_TRANS_CLOSE_COUNT | 3 |
| NDB_API_PK_OP_COUNT | 2 |
| NDB_API_UK_OP_COUNT | 0 |
| NDB_API_TABLE_SCAN_COUNT | 1 |
| NDB_API_RANGE_SCAN_COUNT | 0 |
| NDB_API_PRUNED_SCAN_COUNT | 0 |
| NDB_API_SCAN_BATCH_COUNT | 0 |
| NDB_API_READ_ROW_COUNT | 2 |
| NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2 |
| NDB_API_EVENT_DATA_COUNT | 0 |
| NDB_API_EVENT_NONDATA_COUNT | 0 |
| NDB_API_EVENT_BYTES_COUNT | 0 |
+------------------------------------+----------------+
21 rows in set (0.09 sec)
并非所有计数器都反映在所有 4 组状态变量中。对于事件计数器DataEventsRecvdCount、
NondataEventsRecvdCount和
EventBytesRecvdCount，只有
_injector和mysqld级别的 NDB API 状态变量可用：
mysql> SHOW STATUS LIKE 'ndb_api%event%';
+--------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
| Ndb_api_event_data_count | 0 |
| Ndb_api_event_nondata_count | 0 |
| Ndb_api_event_bytes_count | 0 |
+--------------------------------------+-------+
6 rows in set (0.00 sec)
_injector没有为任何其他 NDB API 计数器实现状态变量，如下所示：
mysql> SHOW STATUS LIKE 'ndb_api%injector%';
+--------------------------------------+-------+
| Variable_name | Value |
+--------------------------------------+-------+
| Ndb_api_event_data_count_injector | 0 |
| Ndb_api_event_nondata_count_injector | 0 |
| Ndb_api_event_bytes_count_injector | 0 |
+--------------------------------------+-------+
3 rows in set (0.00 sec)状态变量的名称可以很容易地与相应计数器的名称相关联。每个 NDB API 统计计数器在下表中列出，并带有描述以及与此计数器对应的任何 MySQL 服务器状态变量的名称。
表 21.61 NDB API 统计计数器
| 柜台名称 | 描述 | 状态变量（按统计类型）：
|
|---|---|---|
WaitExecCompleteCount |
在等待操作执行完成时线程被阻塞的次数。包括所有
execute()
调用以及对客户端不可见的 blob 操作和自动增量的隐式执行。 |
|
WaitScanResultCount |
线程在等待基于扫描的信号时被阻塞的次数，例如等待其他结果或扫描关闭。 | |
WaitMetaRequestCount |
线程被阻塞等待基于元数据的信号的次数；这可能发生在等待 DDL 操作或开始（或结束）纪元时。 | |
WaitNanosCount |
等待来自数据节点的某种类型的信号所花费的总时间（以纳秒为单位）。 | |
BytesSentCount |
发送到数据节点的数据量（以字节为单位） | |
BytesRecvdCount |
从数据节点接收的数据量（以字节为单位） | |
TransStartCount |
开始的事务数。 | |
TransCommitCount |
提交的事务数。 | |
TransAbortCount |
中止的事务数。 | |
TransCloseCount |
中止的事务数。（此值可能大于 和 的总和TransCommitCount。
TransAbortCount） |
|
PkOpCount |
基于或使用主键的操作数。此计数包括 blob 部分表操作、隐式解锁操作和自动增量操作，以及通常对 MySQL 客户端可见的主键操作。 | |
UkOpCount |
基于或使用唯一键的操作数。 | |
TableScanCount |
已启动的表扫描数。这包括内部表的扫描。 | |
RangeScanCount |
已开始的范围扫描数。 | |
PrunedScanCount |
已修剪为单个分区的扫描数。 | |
ScanBatchCount |
收到的批次行数。（此上下文中的 批次是来自单个片段的一组扫描结果。） | |
ReadRowCount |
已读取的总行数。包括使用主键、唯一键和扫描操作读取的行。 | |
TransLocalReadRowCount |
从运行事务的同一节点的数据读取的行数。 | |
DataEventsRecvdCount |
收到的行更改事件数。 |
|
NondataEventsRecvdCount |
收到的事件数，行更改事件除外。 | |
EventBytesRecvdCount |
接收到的事件的字节数。 |
|
要查看已提交事务的所有计数（即所有
TransCommitCount计数器状态变量），您可以过滤
SHOW STATUSsubstring
的结果trans_commit_count，如下所示：
mysql> SHOW STATUS LIKE '%trans_commit_count%';
+------------------------------------+-------+
| Variable_name | Value |
+------------------------------------+-------+
| Ndb_api_trans_commit_count_session | 1 |
| Ndb_api_trans_commit_count_slave | 0 |
| Ndb_api_trans_commit_count | 2 |
+------------------------------------+-------+
3 rows in set (0.00 sec)由此可以确定，在当前mysql客户端会话中已经提交了1个事务， 自从上次重启后， 在这个mysqld上已经提交了2个事务。
_session通过比较执行语句前后
相应状态变量的值，您可以看到给定 SQL 语句如何增加各种 NDB API 计数器
。在此示例中，从 获取初始值后SHOW
STATUS，我们在test
数据库中创建一个NDB名为 的表，
该表t只有一列：
mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+--------+
| Variable_name | Value |
+--------------------------------------------+--------+
| Ndb_api_wait_exec_complete_count_session | 2 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 3 |
| Ndb_api_wait_nanos_count_session | 820705 |
| Ndb_api_bytes_sent_count_session | 132 |
| Ndb_api_bytes_received_count_session | 372 |
| Ndb_api_trans_start_count_session | 1 |
| Ndb_api_trans_commit_count_session | 1 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 1 |
| Ndb_api_pk_op_count_session | 1 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 1 |
| Ndb_api_trans_local_read_row_count_session | 1 |
+--------------------------------------------+--------+
18 rows in set (0.00 sec)
mysql> USE test;
Database changed
mysql> CREATE TABLE t (c INT) ENGINE NDBCLUSTER;
Query OK, 0 rows affected (0.85 sec)
现在您可以执行一条新SHOW
STATUS语句并观察更改，如下所示（更改的行在输出中突出显示）：
mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+-----------+
| Variable_name | Value |
+--------------------------------------------+-----------+
| Ndb_api_wait_exec_complete_count_session | 8 |
| Ndb_api_wait_scan_result_count_session | 0 |
| Ndb_api_wait_meta_request_count_session | 17 |
| Ndb_api_wait_nanos_count_session | 706871709 |
| Ndb_api_bytes_sent_count_session | 2376 |
| Ndb_api_bytes_received_count_session | 3844 |
| Ndb_api_trans_start_count_session | 4 |
| Ndb_api_trans_commit_count_session | 4 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 4 |
| Ndb_api_pk_op_count_session | 6 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 0 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 2 |
| Ndb_api_trans_local_read_row_count_session | 1 |
+--------------------------------------------+-----------+
18 rows in set (0.00 sec)
同样，您可以看到将行插入到 NDB API 统计计数器中的变化t：插入行，然后运行与SHOW
STATUS上一个示例相同的语句，如下所示：
mysql> INSERT INTO t VALUES (100);
Query OK, 1 row affected (0.00 sec)
mysql> SHOW STATUS LIKE 'ndb_api%session%';
+--------------------------------------------+-----------+
| Variable_name | Value |
+--------------------------------------------+-----------+
| Ndb_api_wait_exec_complete_count_session | 11 |
| Ndb_api_wait_scan_result_count_session | 6 |
| Ndb_api_wait_meta_request_count_session | 20 |
| Ndb_api_wait_nanos_count_session | 707370418 |
| Ndb_api_bytes_sent_count_session | 2724 |
| Ndb_api_bytes_received_count_session | 4116 |
| Ndb_api_trans_start_count_session | 7 |
| Ndb_api_trans_commit_count_session | 6 |
| Ndb_api_trans_abort_count_session | 0 |
| Ndb_api_trans_close_count_session | 7 |
| Ndb_api_pk_op_count_session | 8 |
| Ndb_api_uk_op_count_session | 0 |
| Ndb_api_table_scan_count_session | 1 |
| Ndb_api_range_scan_count_session | 0 |
| Ndb_api_pruned_scan_count_session | 0 |
| Ndb_api_scan_batch_count_session | 0 |
| Ndb_api_read_row_count_session | 3 |
| Ndb_api_trans_local_read_row_count_session | 2 |
+--------------------------------------------+-----------+
18 rows in set (0.00 sec)我们可以从这些结果中得出一些结论：
尽管我们创建
t时没有显式主键，但这样做执行了 5 次主键操作（“之前”和 “之后”值 的差异Ndb_api_pk_op_count_session，或 6 减 1）。这反映了隐藏主键的创建，这是使用NDB存储引擎的所有表的一个特性。通过比较 的连续值
Ndb_api_wait_nanos_count_session，我们可以看到实现CREATE TABLE语句的 NDB API 操作等待数据节点响应的时间比INSERT（707370418 - 706871709 = 498709 ns 或大约 0.0005 秒）。在mysql客户端中报告的这些语句的执行时间 与这些数字大致相关。在没有足够（纳秒）时间分辨率的平台上，由于执行速度非常快的 SQL 语句导致的 NDB API 计数器值的微小变化
WaitNanosCount可能并不总是在 、 或 的值Ndb_api_wait_nanos_count_session中Ndb_api_wait_nanos_count_slave可见Ndb_api_wait_nanos_count。该
INSERT语句增加了ReadRowCount和TransLocalReadRowCountNDB API 统计计数器，这反映在 和 的增加值Ndb_api_read_row_count_session上Ndb_api_trans_local_read_row_count_session。