kll_sketch_get_rank_float function

Applies to: Databricks Runtime 18.0 and later

Estimates the normalized rank (0.0 to 1.0) of a given value in a float KLL sketch.

Syntax

kll_sketch_get_rank_float ( sketch, value )

Arguments

• sketch: A BINARY expression containing a serialized FLOAT KLL sketch.
• value: A FLOAT expression or ARRAY<FLOAT> of values to find ranks for.

Returns

• If value is FLOAT: returns a DOUBLE between 0.0 and 1.0 representing the normalized rank.
• If value is ARRAY<FLOAT>: returns ARRAY<DOUBLE> with ranks for each value.

Notes

• The rank represents the fraction of values in the sketch that are less than or equal to the given value.
• Returns 0.0 if all sketch values are greater than the input value.
• Returns 1.0 if all sketch values are less than or equal to the input value.

Examples

SQL

> WITH sketch_data AS (
    SELECT kll_sketch_agg_float(score) AS sketch
    FROM VALUES (1.5), (2.3), (3.7) AS T(score)
  )
  SELECT kll_sketch_get_rank_float(sketch, 2.5) FROM sketch_data
  0.66

Related functions

• kll_sketch_agg_float aggregate function
• kll_sketch_get_rank_bigint function
• kll_sketch_get_rank_double function