Salesforce Upsert inserting lot more records

I am using salesforce upsert snap to insert records for a salesforce object, which currently has no records. The snap takes all the time in the world to complete execution. And when it does, it inserts a lot more records, although the mapper snap has only data only for one record.
I haven’t change any default settings in the snap, except for providing the object name for which records are to be upserted.
Any help would be appreciated.

Since data preview only works with the first 50 records, your pipeline may only find 1 record in those 50 records that match the requirements of your pipeline, but when you execute the pipeline, it may find other records in the rest of your data.

Hi Diana,
Thanks for your quick reply. Actually, the problem is happening only when there are no records for the salesforce object. Thereafter, the behaviour is as expected.

I am puzzled by this.