Elasticsearch rejects records without timestamp

I am loading log records from mysql log files - into [filebeat-]YYYY.MM.DD indexes (through the logstash and related filters) - most of the records are coming in but some are rejected due to missing time stamp - which happens as not all records from mysql log files have time stamps - most do but not all ...

What is the best way to get these records in - should the index be different or should the records be modified in logstash filters to append timestmap or ..?


Ideally, yes.

Thank you