tuple_union_double function

Applies to: Databricks Runtime 18.1 and above

Merges exactly two TupleSketch binary representations with double summaries using set union.

Syntax

tuple_union_double ( first, second [, lgNomEntries [, mode ]] )

Arguments

• first: A TupleSketch in binary format with double summaries.
• second: A TupleSketch in binary format with double summaries.
• lgNomEntries: An optional INTEGER literal specifying the log-base-2 of nominal entries. Must be between 4 and 26, inclusive. The default is 12.
• mode: An optional STRING literal specifying the aggregation mode. Valid values: 'sum', 'min', 'max', 'alwaysone'. The default is 'sum'.

Returns

A BINARY value containing the merged TupleSketch with double summaries.

Notes

• For merging more than two sketches, use the aggregate tuple_union_agg_double function.

Error messages

• TUPLE_INVALID_INPUT_SKETCH_BUFFER

Examples

> SELECT tuple_sketch_estimate_double(
    tuple_union_double(
      tuple_sketch_agg_double(col1, val1),
      tuple_sketch_agg_double(col2, val2)
    )
  ) FROM VALUES (1, 1.0D, 4, 4.0D), (2, 2.0D, 5, 5.0D), (3, 3.0D, 6, 6.0D) tab(col1, val1, col2, val2);
6.0

Related

• tuple_union_integer function
• tuple_union_agg_double aggregate function