In HSEARCH-3047 In Progress , we added support for many temporal types, but we opted to stick to millisecond resolution for index and doc values, to match what Elasticearch 6 can offer. Nanosecond precision is only supported for projections.

We should allow users to switch to nanoseconds precision on an opt-in basis.

One way to do that would be to offer an `@TemporalField` annotation in the mapping, so that users can simply write @TemporalField(resolution = Resolution.NANOSECOND.

We would have to add support for that resolution in the backends.

In Elasticsearch, we cannot do that before ES7, which introduces the date_nanos datatype: https://www.elastic.co/guide/en/elasticsearch/reference/master/date_nanos.html . Let's just throw exceptions for older versions of ES.

In Lucene, that would probably mean storing the data as a string, like we used to do in Search 5. But maybe ES7 has a better solution, so let's have a look.

Important: be sure to use Resolution.DEFAULT as the default, not Resolution.MILLISECOND, so that we can one day provide an option to set the default resolution in the backend options.