To use this aggregator, make sure you the extension in your config file:

  2.   "type" : "arrayOfDoublesSketch",
  3.   "name" : <output_name>,
  4.   "fieldName" : <metric_name>,
  5.   "nominalEntries": <number>,
  6.   "numberOfValues" : <number>,
  7.   "metricColumns" : <array of strings>
  8.  }

Post Aggregators

Estimate of the number of distinct keys

Returns a distinct count estimate from a given ArrayOfDoublesSketch.

  1.   "type"  : "arrayOfDoublesSketchToEstimate",
  2.   "name": <output name>,
  3.   "field"  : <post aggregator that refers to an ArrayOfDoublesSketch (fieldAccess or another post aggregator)>
  4. }

Estimate of the number of distinct keys with error bounds

Number of retained entries

Returns the number of retained entries from a given ArrayOfDoublesSketch.

  1. {
  3.   "name": <output name>,
  4.   "field"  : <post aggregator that refers to an ArrayOfDoublesSketch (fieldAccess or another post aggregator)>
  5. }

Mean values for each column

Returns a list of mean values from a given ArrayOfDoublesSketch. The result will be N double values, where N is the number of double values kept in the sketch per key.

  1. {
  2.   "type"  : "arrayOfDoublesSketchToMeans",
  3.   "name": <output name>,
  4.   "field"  : <post aggregator that refers to a DoublesSketch (fieldAccess or another post aggregator)>
  5. }

Variance values for each column

Quantiles sketch from a column

Returns a quantiles DoublesSketch constructed from a given column of values from a given ArrayOfDoublesSketch using optional parameter k that determines the accuracy and size of the quantiles sketch. See

  • The column number is 1-based and is optional (the default is 1).
  • The parameter k is optional (the default is defined in the sketch library).
  • The result is a quantiles sketch.
  1. {
  2.   "name": <output name>,
  3.   "field"  : <post aggregator that refers to a DoublesSketch (fieldAccess or another post aggregator)>,
  4.   "column" : <number>,
  6. }

Set Operations

Returns a result of a specified set operation on the given array of sketches. Supported operations are: union, intersection and set difference (UNION, INTERSECT, NOT).

  1. {
  2.   "type"  : "arrayOfDoublesSketchSetOp",
  3.   "name": <output name>,
  4.   "operation": <"UNION"|"INTERSECT"|"NOT">,
  5.   "fields"  : <array of post aggregators to access sketch aggregators or post aggregators to allow arbitrary combination of set operations>,
  6.   "nominalEntries" : <parameter that determines the accuracy and size of the sketch>,
  7.   "numberOfValues" : <number of values associated with each distinct key>
  8. }

Student’s t-test

Sketch summary

Returns a human-readable summary of a given ArrayOfDoublesSketch. This is a string returned by toString() method of the sketch. This can be useful for debugging.

  1. {
  2.   "type"  : "arrayOfDoublesSketchToString",
  3.   "name": <output name>,
  4.   "field"  : <post aggregator that refers to an ArrayOfDoublesSketch (fieldAccess or another post aggregator)>