How the continuous transform job skip the already read document from an index

implementedVersions (relevant - OpenSearch/Dashboard/Server OS/Browser):
OpenSearch 2.9.0

Describe the issue:
I have created a transform job which is continuously running in every hour. There is no range filter added in the data_selection_query, so that it will read all the documents in the index. Will this transform job read and aggregate the already read document from the index when it run for the sencond time? If no, how the transform job is tracking the already read document? Are we saving the state of documents any where?


Relevant Logs or Screenshots: