flink-doris-connector写入doris，transactions没有变化

doris：2.0.12
flink-doris-connector：1.17-1.5.0

执行show proc '/transactions'命令，transactions一直都是3没有变化，正常来说事务提交后transactions应该会减少，请问这是什么原因呢？

flink配置，并行度3

SET 'execution.checkpointing.interval' = '5min';
SET 'execution.checkpointing.min-pause' = '10s';

doris配置

'sink.label-prefix'='xxx',
'sink.properties.format' = 'csv',
'sink.properties.column_separator' = ',',
'sink.properties.columns' = 'user_id=to_bitmap(user_id)'