[TSVB] Inability to use value_count aggregation on non-numeric fields

[lucabelluccini]

Kibana version: 7.6.2, 7.7.0 (probably more versions affected)

Elasticsearch version: 7.6.2, 7.7.0

Describe the bug:

When using TSVB and we want to use the value_count, the UI allows to select only numerical fields, while I would expect to work on keyword fields.

Steps to reproduce:

1. Create some dummy documents

PUT discuss/_doc/1
{
  "timestamp" : "2020-01-19T03:26:21.326Z",
  "fruits": "banana",
  "test": 1
}
PUT discuss/_doc/2
{
  "timestamp" : "2020-01-19T03:26:21.326Z",
  "fruits": "banana",
  "test": 1
}
PUT discuss/_doc/3
{
  "timestamp" : "2020-01-19T03:26:21.326Z",
  "fruits": "apple",
  "test": 1
}
PUT discuss/_doc/4
{
  "timestamp" : "2020-01-19T03:26:21.326Z",
  "fruits": ["apple", "banana", "orange"],
  "test": 1
}

2. Create the index pattern, select timestamp as time field

3. Create a TSVB (Metric) with:

• Panel options (Entire time range, discuss index pattern, drop last bucket false, timestamp time field)
• Data (Value count, Group by everything)

4. You will notice it is not possible to select fruits, but only test.

Expected behavior:

I would like to be able to use fruits field.

Screenshots (if relevant):

Related:

• [Meta] Kibana support for ES aggregations #58628
• https://discuss.elastic.co/t/how-to-merge-two-search-values-two-a-single-one/234590/6

[lucabelluccini]

Maybe we're missing value_count in

kibana/src/plugins/vis_type_timeseries/common/metric_types.js

Line 20 in 74b9ed6

export const METRIC_TYPES = {

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)