Gabor Kaszab created IMPALA-9632:
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Summary: Implement ds_hll_sketch() and ds_hll_estimate() functions
Key: IMPALA-9632
URL: https://issues.apache.org/jira/browse/IMPALA-9632
Project: IMPALA
Issue Type: New Feature
Components: Backend, Frontend
Reporter: Gabor Kaszab
These should be built-in functions that use DataSketches functionality that was
integrated by [IMPALA-9631|https://issues.apache.org/jira/browse/IMPALA-9631].
ds_hll_sketch() should receive a primitive expression and return a sketch.
ds_hll_estimate() should receive a sketch and return a primitive that is the
cardinality estimate for that set of data provided to the sketch.
Usage:
select ds_hll_estimate(ds_hll_sketch(col_name)) from table_name;
Returns a cardinality estimate (similarly to ndv() ) for that particular column.
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