clintropolis opened a new pull request, #15550:
URL: https://github.com/apache/druid/pull/15550

   ### Description
   Removes the 'auto' strategy from the native search query to simplify 
`BitmapColumnIndex` to remove the `estimateSelectivity` method. The 'auto' 
strategy is not on by default, and in some cases can be rather expensive since 
for logical filters like AND/OR we fetch all of the indexes, compute the 
cardinality of each of them, and then throw them away, sometimes to turn around 
and do the same thing again to actually use the indexes.
   
   The replacement for this will be smarter usage of indexes for all query 
types, as a follow-up I plan to bring the enhancements of #13977 to classic 
string typed columns, and I've got some additional improvements coming in the 
future.
   
   [Related dev mailing list 
thread](https://lists.apache.org/thread/8lbgbo2977c88xxp714znmkg3w2lbkdj)
   
   (This release note is currently a lie, but a follow-up PR will make it more 
true.)
   
   #### Release note
   The 'auto' strategy has been removed from the [search 
query](https://druid.apache.org/docs/latest/querying/searchquery). Specifying 
'auto' will now be equivalent to specifying 'useIndexes'. Improvements to how 
and when indexes are computed in general have allowed 'useIndexes' to benefit 
and be more adaptive when it uses indexes for filter processing, skipping 
computing expensive indexes when possible.
   
   <hr>
   
   This PR has:
   
   - [x] been self-reviewed.
   - [x] added documentation for new or modified features or behaviors.
   - [x] a release note entry in the PR description.
   - [x] been tested in a test Druid cluster.
   


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