date histogram limitations

[PSeitz]

Date histogram aggregation has been added in https://github.com/quickwit-oss/tantivy/pull/1900 with some limitations:

only fixed_interval is supported, calendar-aware features like calendar_interval are not supported
format is unsupported. Fixed to Rfc3339 currently.
bounds are not yet supported to be provided via String, e.g. "2015-01-01T00:00:00Z"

Calendar-aware intervals

Calendar-aware intervals understand that daylight savings changes the length of specific days, months have different amounts of days, and leap seconds can be tacked onto a particular year.

https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html

[fulmicoton]

calendar_interval are required for opendashboard, so raising the priority.

Obviously we want the fixed interval optimization whenever possible (1w, 1d, etc.) and I think we can ignore leap seconds for the moment.

[PSeitz]

https://github.com/quickwit-oss/tantivy/issues/2459