User should be able to specify the datetime field format for printing

[CaptainDredge]

Is your feature request related to a problem? Please describe.
Currently, in case of multiple datetime field formats either specified by user or as part of default datetime format the stored milliseconds-since-the-epoch gets converted back to string using the first format whenever any search query is made. For eg. if the documents have datetime field without any user specified format and the value of the datetime field in the doc is in epoch_millis format but when the epoch get converted back to string during search it'll always be printed in strict_date_optional_time format because in the default date format "strict_date_optional_time||epoch_millis" optional time format is the first one.

This implicit assumption has been stated in ES public documentation

Describe the solution you'd like
User should be able to define a print format in the datetime field mapping

[peternied]

• Looks like this was fixed in Added performance improvement for datetime field parsing #9567, please reopen if this wasn't the case - thanks for the contribution!