Is your feature request related to a problem or challenge?
approx_distinct returns a not implemented error when the input column has a Dictionary type (e.g. Dictionary(Int32, Utf8)), which is common for low-cardinality string columns stored in Parquet or produced by joins/filters.
Today
SELECT approx_distinct(dict_col) FROM t;
Error: Support for 'approx_distinct' for data type Dictionary(Int32, Utf8) is not implemented
Describe the solution you'd like
approx_distinct uses create_hashes internally (via HLLAccumulator and HllGroupsAccumulator), which already handles Dictionary arrays correctly by hashing the logical decoded values. The fix is to route Dictionary(_, _) to HLLAccumulator
Describe alternatives you've considered
No response
Additional context
No response
Is your feature request related to a problem or challenge?
approx_distinct returns a not implemented error when the input column has a Dictionary type (e.g. Dictionary(Int32, Utf8)), which is common for low-cardinality string columns stored in Parquet or produced by joins/filters.
Today
SELECT approx_distinct(dict_col) FROM t;Error: Support for 'approx_distinct' for data type Dictionary(Int32, Utf8) is not implementedDescribe the solution you'd like
approx_distinctuses create_hashes internally (viaHLLAccumulatorandHllGroupsAccumulator), which already handles Dictionary arrays correctly by hashing the logical decoded values. The fix is to routeDictionary(_, _)to HLLAccumulatorDescribe alternatives you've considered
No response
Additional context
No response