[GitHub] [druid] clintropolis edited a comment on issue #9791: Introduce extensibility support for Datasources

[GitBox <gi...@apache.org>]

clintropolis edited a comment on issue #9791:
URL: https://github.com/apache/druid/issues/9791#issuecomment-622243481


   >The UnionDataSource can be refactored to be an implementation of this interface and the getSegmentsFromIntervals method would return all the segments from all the datasources defined in the union query.
   
   How does this work? I guess the broker needs to keep track of which segments are for which timeline and which sub part of the union query? Does it potentially issue multiple queries to a single server instead of the current single query per historical/peon with specific segment spec that it does now? 
   >the broker can identify segments to be retrieved from all the requested datasources at the same time therefore the queries to the historical will now include segment specs from all the datasources requested in the union query
   
   Based on ^, I guess not, but If not, how does the broker distinguish which results belong to which timeline? I'm having trouble imagining how this works in practice without making caching clustered client know a lot more about the query than it currently does, but maybe I haven't though hard enough about this yet.


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