the uniqueSource in StreamExecution, where is it be changed please?

[??????????]

Hi all,


These days I am learning the code about the StreamExecution.
In the method constructNextBatch(about line 365), I found the value of 
latestOffsets changed but I can not find where the s.getOffset of uniqueSource 
is  changed.
here is the code link:


https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/StreamExecution.scala



Would you like help understand it please?


Thanks.
Robin