I have various fields in my data that are in epoch_millis (long). Is it possible to create a mapping that converts this long into a proper date field when it gets ingested in Elasticsearch?
If you want to change the format in the source document, you can use an ingest pipeline with a date processor. If you want to keep the format in the document but make sure it is indexed as a date, you can map it as a date with the correct format. A mapping does not alter the content of the indexed document, just how it is interpreted and indexed.
Brilliant, thank you Christian!