kll_sketch_agg_double aggregate function

Applies to: check marked yes Databricks Runtime 18.0 and later

Creates a KLL (Karnin-Lang-Liberty) sketch for approximate quantile estimation on double precision floating-point data with configurable accuracy.

Syntax

kll_sketch_agg_double ( expr [, k] )

Arguments

  • expr: A DOUBLE expression to aggregate.
  • k: An optional INTEGER literal controlling sketch accuracy. Must be between 8 and 65535. The default is 200. Higher values provide better accuracy but use more memory.

Returns

A BINARY value containing the serialized KLL sketch for DOUBLE data.

Notes

  • NULL values in expr are ignored during aggregation.
  • NaN values are handled according to IEEE 754 semantics.
  • The sketch provides approximate quantiles with a confidence level of about 99%.
  • Preferred for high-precision quantile estimation.

Examples

-- Create sketch from double values
> SELECT kll_sketch_agg_double(measurement) FROM VALUES (1.23456), (2.34567) AS T(measurement)
  [binary data]
  • Last updated on