Rich-T-kid opened a new issue, #24730:
URL: https://github.com/apache/datafusion/issues/24730
### 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_
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