highestMax() function

The highestMax() function selects the maximum record from each table in the input stream and returns the top n records. It outputs a single aggregated table containing n records.

*Function type: Selector, Aggregate*

highestMax(
  n:10,
  column: "_value",
  groupColumns: []
)

Empty tables

highestMax() drops empty tables.

Parameters

n

Number of records to return.

*Data type: Integer*

column

Column by which to sort. Default is "_value".

*Data type: String*

groupColumns

The columns on which to group before performing the aggregation. Default is [].

*Data type: Array of strings*

Examples

from(bucket:"example-bucket")
  |> range(start:-1h)
  |> filter(fn: (r) =>
    r._measurement == "mem" and
    r._field == "used_percent"
  )
  |> highestMax(n:10, groupColumns: ["host"])

Function definition

// _sortLimit is a helper function, which sorts and limits a table.
_sortLimit = (n, desc, columns=["_value"], tables=<-) =>
  tables
    |> sort(columns:columns, desc:desc)
    |> limit(n:n)
// _highestOrLowest is a helper function which reduces all groups into a single
// group by specific tags and a reducer function. It then selects the highest or
// lowest records based on the column and the _sortLimit function.
// The default reducer assumes no reducing needs to be performed.
_highestOrLowest = (n, _sortLimit, reducer, column="_value", groupColumns=[], tables=<-) =>
  tables
    |> group(columns:groupColumns)
    |> reducer()
    |> group(columns:[])
    |> _sortLimit(n:n, columns:[column])
highestMax = (n, column="_value", groupColumns=[], tables=<-) =>
  tables
    |> _highestOrLowest(
        n:n,
        column:column,
        groupColumns:groupColumns,
        reducer: (tables=<-) => tables |> max(column:column),
        _sortLimit: top
      )