77.MySQL中如何查看一个事务的大小

比如要查看：SET @@SESSION.GTID_NEXT= '43e4cdae-2fa1-11ee-9049-000c29318629:2886' 这个事务的大小，可以通过binbog日志进行查看

root@mysqldb 20:40:  [(none)]> pager grep 'Gtid\|COMMIT';
PAGER set to 'grep 'Gtid\|COMMIT''
root@mysqldb 20:46:  [(none)]> show binlog events in 'mybinlog.000030';
| mybinlog.000030 |      196 | Gtid           |   1463306 |         275 | SET @@SESSION.GTID_NEXT= '43e4cdae-2fa1-11ee-9049-000c29318629:2885' |
| mybinlog.000030 |      496 | Xid            |   1463306 |         527 | COMMIT /* xid=25 */                                                  |
| mybinlog.000030 |      527 | Gtid           |   1463306 |         606 | SET @@SESSION.GTID_NEXT= '43e4cdae-2fa1-11ee-9049-000c29318629:2886' |
| mybinlog.000030 |      827 | Xid            |   1463306 |         858 | COMMIT /* xid=27 */                                                  |
| mybinlog.000030 |      858 | Gtid           |   1463306 |         943 | SET @@SESSION.GTID_NEXT= '43e4cdae-2fa1-11ee-9049-000c29318629:2887' |
| mybinlog.000030 | 32926813 | Xid            |   1463306 |    32926844 | COMMIT /* xid=36 */                                                  |
4029 rows in set (0.07 sec)

可以看到这个事务大小有31M

root@mysqldb 20:55:  [(none)]> pager
Default pager wasn't set, using stdout.
root@mysqldb 20:55:  [(none)]> select format_bytes(32926813 - 858);
+-----------------------------+
| format_bytes(32926813 - 858) |
+-----------------------------+
| 31.40 MiB                   |
+-----------------------------+

这样就计算出了binlog event的大小。但是这种这种方式还是很麻烦，尤其是想要找出某个事物的大小，可能需要查看多个binlog日志文件。

这里可以采用performance_schema中binary_log_transaction_compression_stats获得有关事务大小的信息。

 select format_bytes(UNCOMPRESSED_BYTES_COUNTER/TRANSACTION_COUNTER) size,format_bytes(COMPRESSED_BYTES_COUNTER/TRANSACTION_COUNTER) compressed,TRANSACTION_COUNTER from performance_schema.binary_log_transaction_compression_stats;
+-----------+------------+---------------------+
| size      | compressed | TRANSACTION_COUNTER |
+-----------+------------+---------------------+
| 20.81 MiB | 20.81 MiB  |                   1 |

注意：要查看sql语句的大小，一定要把这个表先清空，然后再执行sql语句，最后再用这条sql语句进行查看这条事务的大小

truncate table performance_schema.binary_log_transaction_compression_stats;

此外还可以使用MySQL shell plugin列出binlog中binlog事件大小。

 MySQL  db04:33060+ ssl  JS > check.showTrxSizeSort()
Transactions in binary log mybinlog.000030 orderer by size (limit 10):
31 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2887
252 bytes - 43e4cdae-2fa1-11ee-9049-000c29318629:2886
252 bytes - 43e4cdae-2fa1-11ee-9049-000c29318629:2885
20 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2888
20 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2892
20 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2890
20 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2891
20 mb - 43e4cdae-2fa1-11ee-9049-000c29318629:2889