rluvaton opened a new pull request, #17967:
URL: https://github.com/apache/datafusion/pull/17967
## Which issue does this PR close?
N/A
## Rationale for this change
the benchmark did not test what it expected, i.e. `u64_wide` was the same in
every batch.
I run this query for the data:
```
SELECT
COUNT(*) AS total_count,
COUNT(DISTINCT u64_wide) AS unique_count,
COUNT(DISTINCT u64_wide) * 1.0 / COUNT(*) AS cardinality
FROM t;
```
Before:
```
| total_count | unique_count | cardinality |
| ----------- | ------------ | ----------- |
| 65536 | 2048 | 0.03125 |
```
After:
```
| total_count | unique_count | cardinality |
| ----------- | ------------ | ----------- |
| 65536 | 65536 | 1.0 |
```
## What changes are included in this PR?
used the batch random when generating u64_wide and added another benchmark
for testing pure grouping performance for more than 1 column.
## Are these changes tested?
No need
## Are there any user-facing changes?
Nope
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