When ingesting data from an S3 data source, it is most likely that you will ingest multiple different files over time. In some cases, it might be necessary to find out from which file a specific record originated.
Each table that the S3 data source creates includes two fields:
__s3key. These fields, respectively, indicate the name of the source bucket and file where the data was extracted.
Note that if the same record is updated, the values of these fields will point to the latest bucket and file that actually updated that record.