ElasticGraph Query API: Aggregated Values

Aggregated values can be computed from all values of a particular field from all documents backing an aggregation node. Here’s an example:

query BluegrassArtistLifetimeSales {
  artistAggregations(
    filter: {bio: {description: {matchesQuery: {query: "bluegrass"}}}}
  ) {
    nodes {
      groupedBy {
        bio { yearFormed }
      }

      aggregatedValues {
        lifetimeSales {
          exactMin
          exactMax

          exactSum
          approximateSum

          approximateAvg
        }
      }
    }
  }
}

This example query aggregates the values of the Artist.lifetimeSales field using all 4 of the standard numeric aggregated values: min, max, avg, and sum. These are qualified with approximate or exact to indicate the level of precision they offer. The documentation for approximateSum and exactSum provide more detail:

approximateSum

The (approximate) sum of the field values within this grouping.

Sums of large Int values can result in overflow, where the exact sum cannot fit in a JsonSafeLong return value. This field, as a double-precision Float, can represent larger sums, but the value may only be approximate.

exactSum

The exact sum of the field values within this grouping, if it fits in a JsonSafeLong.

Sums of large Int values can result in overflow, where the exact sum cannot fit in a JsonSafeLong. In that case, null will be returned, and approximateSum can be used to get an approximate value.

Besides these standard numeric aggregated values, ElasticGraph offers one more:

query SkaArtistHomeCountries {
  artistAggregations(
    filter: {bio: {description: {matchesQuery: {query: "ska"}}}}
  ) {
    nodes {
      groupedBy {
        bio { yearFormed }
      }

      aggregatedValues {
        bio {
          homeCountry {
            approximateDistinctValueCount
          }
        }
      }
    }
  }
}

The approximateDistinctValueCount field uses the HyperLogLog++ algorithm to provide an approximate count of distinct values for the field. In this case, it can give us an idea of how many countries ska bands were formed in, in each year.