LakshSingla opened a new pull request, #16825:
URL: https://github.com/apache/druid/pull/16825
### Description
This PR fixes queries like
```sql
SELECT COUNT(DISTINCT json_col) FROM foo
```
when run using MSQ.
The frames delegate the `classOfObject` to
`ComplexMetricSerde.getExtractor()` which isn't implemented for JSON columns
and is probably not the right way to fetch the class of the complex type. A
better alternative is to use the object type strategy to fetch the class, which
is implemented for every complex serde. This PR modifies the field reader and
the column readers to use the latter method.
<hr>
##### Key changed/added classes in this PR
* `MyFoo`
* `OurBar`
* `TheirBaz`
<hr>
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- [ ] added or updated version, license, or notice information in
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- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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