[Index Patterns] Disallow nested field time field?

[Dosant]

version: up to 7.13/master

Kibana has limited nested field support: #1084

Index pattern editor allows creating of an index pattern with nested field time field, but looks like this shouldn't be possible, because Discover fails with an error when it tries to build a data aggregation:

Uncaught Error: Saved field "nested.timeField" of index pattern "my-index-pattern" is invalid for use with the "Date Histogram" aggregation. Please select a new field.

Alternatively, maybe we should treat such index patterns as non-time-based?

cc @mattkime @kertal

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServices)

[mattkime]

I suspect this problem could happen elsewhere as nested field query and aggregation support is a bit unique - https://www.elastic.co/guide/en/elasticsearch/reference/current/nested.html#nested-accessing-documents

IMO, this is part of a larger 'supporting nested fields' effort.

Hm, are these fields available in the index pattern timestamp field selection but filtered out of the index pattern field list?

[Dosant]

Hm, are these fields available in the index pattern timestamp field selection but filtered out of the index pattern field list?

@mattkime, this is the particular Discover error I looked at: #103083

When Discover builds its date histogram chart it fails to build an aggregation.
Digging deeper, this is the condition that prevents such aggregation to be built:

kibana/src/plugins/data/common/search/aggs/param_types/field.ts

Line 132 in d44f9fe

(onlyAggregatable && (!field.aggregatable || isNestedField(field))) ||

And this when this check was added: #54820
I wonder if that change was more focused on visualize and that agg would actually work in discover

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.