clintropolis opened a new pull request, #12855:
URL: https://github.com/apache/druid/pull/12855
### Description
Fixes an issue with the cache key information used to encode ordering for
top n and group by queries, which just refer to the name. However, since many
agg and post-agg implementations do not add the output name to the cache key,
constructing the ordering cache key information just by name is insufficient to
ensure that the cached data is actually sorted in the same manner.
This PR fixes this by appending extra cache information for the inputs of
the ordering information, basically duplicating the key information of the
dimspec, aggregator factory, or postagg as appropriate. Alternatively, we could
have added output name to all agg and postagg cache keys, but it seems like
that could result in slightly lower cache hit rate so this way seems preferable
to me at least.
<hr>
This PR has:
- [ ] been self-reviewed.
- [ ] using the [concurrency
checklist](https://github.com/apache/druid/blob/master/dev/code-review/concurrency.md)
(Remove this item if the PR doesn't have any relation to concurrency.)
- [ ] added documentation for new or modified features or behaviors.
- [ ] added Javadocs for most classes and all non-trivial methods. Linked
related entities via Javadoc links.
- [ ] added or updated version, license, or notice information in
[licenses.yaml](https://github.com/apache/druid/blob/master/dev/license.md)
- [ ] added comments explaining the "why" and the intent of the code
wherever would not be obvious for an unfamiliar reader.
- [ ] added unit tests or modified existing tests to cover new code paths,
ensuring the threshold for [code
coverage](https://github.com/apache/druid/blob/master/dev/code-review/code-coverage.md)
is met.
- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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