Package dev.frostlake.functions.aggregate

Class ApproxTopKAccumulate

java.lang.Object
dev.frostlake.functions.BuiltInFunction
dev.frostlake.functions.AggregateFunction
dev.frostlake.functions.aggregate.ApproxTopKAccumulate
public class ApproxTopKAccumulate extends AggregateFunction
APPROX_TOP_K_ACCUMULATE(expr, counters): the whole TopKSummary of the input as an OBJECT state — {"counters":C,"datatype":T,"precision":P,"scale":S,"state":[[value, count], …], "type":"approx_top_k"} — for APPROX_TOP_K_COMBINE to merge and APPROX_TOP_K_ESTIMATE to rank. Both arguments are required; the counter limit is a constant between 1 and 100000. The datatype is the input's declared type in the catalog's internal vocabulary (FIXED, TEXT, REAL, DATE, BOOLEAN, VARIANT, …), with a NUMBER's own precision and scale and 38/0 for everything else; a state that saw no value reports one counter and the 38/0 width whatever was asked (live-verified).

  • Constructor Details

    • ApproxTopKAccumulate

      public ApproxTopKAccumulate()

  • Method Details

    • createAccumulator

      public AggregateFunction.Accumulator createAccumulator()
      Description copied from class: AggregateFunction
      Creates the fresh, empty per-group state for one evaluation of this aggregate; the executor makes one per group (or per window partition) and never shares them.
      Specified by:
      createAccumulator in class AggregateFunction
      Returns:
      a new accumulator starting from this aggregate's empty-group state

    • evaluate

      public Object evaluate(List<Object> args)
      Description copied from class: BuiltInFunction
      Computes the function's result over its already-evaluated argument values. A SQL NULL argument arrives as Java null, and returning null makes the SQL result NULL.
      Specified by:
      evaluate in class BuiltInFunction
      Parameters:
      args - the argument values, in call order
      Returns:
      the function's value for these arguments, or null for SQL NULL

    • getMinArgCount

      public int getMinArgCount()
      Description copied from class: BuiltInFunction
      The fewest arguments a call to this function may pass; fewer is an argument-count error.
      Specified by:
      getMinArgCount in class BuiltInFunction
      Returns:
      the minimum accepted argument count

    • getMaxArgCount

      public int getMaxArgCount()
      Description copied from class: BuiltInFunction
      The most arguments a call to this function may pass; Integer.MAX_VALUE marks a variadic function (see BuiltInFunction.isVariadic()).
      Specified by:
      getMaxArgCount in class BuiltInFunction
      Returns:
      the maximum accepted argument count