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Applies to: 
Databricks Runtime 18.1 and above
Returns the estimated number of unique keys from a TupleSketch with double summaries.
Syntax
tuple_sketch_estimate_double ( sketch )
Arguments
- sketch: A TupleSketch in binary format with double summaries.
Returns
A DOUBLE value representing the estimated distinct count of keys.
Error messages
Examples
> SELECT tuple_sketch_estimate_double(tuple_sketch_agg_double(key, summary)) FROM VALUES (1, 1.0D), (1, 2.0D), (2, 3.0D) tab(key, summary);
2.0