How to give date format if there are empty values for the same in indexed document?

If you map a date field in mapping.json but the indexed document has empty date field then the document will not be indexed due to the limitation in elasticsearch. Please use the following collection mapping file, if there are empty fields in the date field by adding  "ignore_malformed": true , to ignore malformed or empty data.

  "revision_date":{
  "type":"date",
  "store":true,
  "ignore_malformed": true
  },

To learn more on custom date fields in search read: Custom Date Fields in Search