Sort terms agg by percentiles including decimal point

[flash1293]

It's possible to sort a terms agg by a nested percentiles metric using the .<percentile value> (e.g. .95) suffix to select the right value out of the multi metric.

{
  "aggs": {
    "terms": {
      "terms": {
        "field": "geo.src",
        "size": 10,
        "order": {
          "percentiles.95": "asc"
        }
      },
      "aggs": {
        "percentiles": {
          "percentiles": {
            "field": "bytes",
            "percents": [
              95
            ]
          }
        }
      }
    }
  },
  "size": 0
}

However for percentiles including a decimal point this doesn't work because of limitations of bucket path parsing. E.g. for 95.3, neither the suffix .95.3 nor ['95.3'] work.

[elasticmachine]

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

[polyfractal]

Note to whomever looks at this bug in the future: pipeline aggs allow the ['foo'] syntax for things like selecting terms from a terms agg... but that uses a different resolution process than the sort resolution in the terms agg, hence the disparity

[wylieconlon]

If we're defining the ideal API, I would expect the syntax percentiles['99.5'] to work. Another option is doing a string replacement like percentiles.99_5 so that it's a valid key.

[drewdaemon]

From @not-napoleon : this is the place to look.