https://drill.apache.org/apidocs/org/apache/drill/exec/expr/fn/impl/StatisticsAggrFunctions.HllFieldReader.html
StatisticsAggrFunctions.HllFieldReader (Drill : 1.22.0 API)
declaration: package: org.apache.drill.exec.expr.fn.impl, class: StatisticsAggrFunctions, class: HllFieldReader
drillapi