alamb opened a new issue, #5547:
URL: https://github.com/apache/arrow-datafusion/issues/5547
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
Queries like this (which compute distinct values for high cardinality
columns) are currently relatively slow (if there are many values of `UserID`):
```
SELECT
SUM(EngineId),
COUNT(*) AS c,
COUNT(DISTINCT "UserID")
FROM
hits
GROUP BY
"RegionID"
ORDER BY
c DESC
LIMIT 10;
```
Here is a specific clickbench query from the discussion on
https://github.com/apache/arrow-datafusion/issues/5276
```sql
❯ SELECT "RegionID", SUM("AdvEngineID"), COUNT(*) AS c,
AVG("ResolutionWidth"), COUNT(DISTINCT "UserID") FROM hits GROUP BY "RegionID"
ORDER BY c DESC LIMIT 10;
```
**Describe the solution you'd like**
We could make this type of query faster. Hopefully we can collect ideas here
**Describe alternatives you've considered**
TBD
**Additional context**
This is one area where clickhouse and duckdb are particularly strong
See https://github.com/apache/arrow-datafusion/issues/5276 and
https://github.com/apache/arrow-datafusion/issues/5276#issuecomment-1433650162
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