leventov opened a new issue #8187: Problematic separation between 
IndexerMetadataStorageCoordinator and MetadataSegmentManager abstractions
URL: https://github.com/apache/incubator-druid/issues/8187
 
 
   Several methods from `IndexerMetadataStorageCoordinator`, namely
    - `getUsedSegmentsForInterval`
    - `getAllUsedSegments`
    - `getUsedSegmentsAndCreatedDates`
    - `getUsedSegmentsForIntervals`
    - `getveUnusedSegmentsForInterval`
   
   Duplicate the `MetadataSegmentManager`'s functionality and look like much 
better suited for the latter class.
   
   The conceptual difference is that `MetadataSegmentManager` caches the 
segments' data in memory, while `IndexerMetadataStorageCoordinator` always 
accesses the metadata store. This difference should be retained, but there 
should be comments to those methods, as well as parallel methods returning 
cached metadata with warnings and guidance regarding which method to use. For 
example, `MaterializedViewSupervisor` uses the methods from 
`IndexerMetadataStorageCoordinator` which seems unnecessary to me (could use 
the methods from `MetadataSegmentManager` instead).
   
   If we decide that "cached metadata - direct access to metadata store" is the 
separation principle between `IndexerMetadataStorageCoordinator` and 
`MetadataSegmentManager`, then this fact should be reflected in these 
interfaces' names, Javadocs, and `retrieveAllDataSourceNames()` method should 
be moved from `MetadataSegmentManager` to `IndexerMetadataStorageCoordinator`.

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