[DOCS] Clarify supported rollup fields

[jrodewig]

Notes that in a rollup config:

• terms support text fields with fielddata enabled.
• metrics support date and date_nanos fields.
• unsigned_long fields are not supported.

Relates to #69582

CC @jloleysens. This may impact field type validation for the potential rollup UI.

Preview

https://elasticsearch_70045.docs-preview.app.elstc.co/guide/en/elasticsearch/reference/master/rollup-api.html

[jrodewig]

There seems to be a minor bug with date_nanos fields. Here's reproduction steps:

// Map a date_nanos field.
PUT my-index-000001
{
  "mappings": {
    "properties": {
      "my-date-nanos-field": {
        "type": "date_nanos" 
      }
    }
  }
}

// Index a document with the date_nanos field.
POST my-index-000001/_doc
{ 
  "@timestamp": "2099-11-15T13:12:00",
  "my-date-nanos-field": "2015-01-01T12:10:30.123456789Z"
}

// Attempt to roll up the index with the date_nanos field as a metric.
POST my-index-000001/_rollup/rollup-my-index-000001
{
  "groups": {
    "date_histogram": {
      "field": "@timestamp",
      "calendar_interval": "1d"
    }
  },
  "metrics": [
    {
      "field": "my-date-nanos-field",
      "metrics": [
        "min",
        "max"
      ]
    }
  ]
}

The rollup attempt returns an error:

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "trying to convert a known date time formatter to a nanosecond one, wrong field used?"
      }
    ],
    "type" : "exception",
    "reason" : "Unable to rollup index [my-index-000001]",
    "caused_by" : {
      "type" : "exception",
      "reason" : "[my-index-000001/9DveCFw8RR67S2tul3Qt_w][[my-index-000001][0]] org.elasticsearch.action.support.broadcast.BroadcastShardOperationFailedException:",
      "caused_by" : {
        "type" : "illegal_argument_exception",
        "reason" : "trying to convert a known date time formatter to a nanosecond one, wrong field used?"
      }
    }
  },
  "status" : 500
}

This seems to be the case even if an epoch_millis format is used.

[jrodewig]

^^ @talevy

[talevy]

I will take a look. thank you!

[talevy]

I opened #70161

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[talevy]

should we highlight what this additional field would be used for? as in, why it is required: metrics.

[jrodewig]

Thanks for the suggestion. Added with 983eb07

[talevy]

I will take a look. thank you!

[talevy]

I opened #70161

[talevy]

@jrodewig also spoke on #70161. I am not entirely sure if we should even support date or date_nanos as metrics. So maybe we should watch this space. it may change

[talevy]

@jrodewig also spoke on #70161. I am not entirely sure if we should even support date or date_nanos as metrics. So maybe we should watch this space. it may change

[jrodewig]

Thanks @talevy. I'll go ahead and merge this in for now. We can easily remove docs for date and date_nanos metrics once #70161 is resolved.

[jloleysens]

Thanks for the heads up @jrodewig !

The added information with respect to the required "metric" field is very useful!