[GitHub] [couchdb] wohali commented on issue #2013: selector filter in _changes API not using indexed search

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wohali commented on issue #2013: selector filter in _changes API not using indexed search
URL: https://github.com/apache/couchdb/issues/2013#issuecomment-486359808
 
 
   That is correct, @subin1011 , there is no way to filter a `_changes` feed on a precalculated secondary index. This is currently technically infeasible given the design of CouchDB. Sorry about that.
   
   What's a Lakh?
   
   Mango selectors are faster than JavaScript functions for filtering a changes feed, but you could try one for comparison.
   
   Remember that the way the _changes feed works is that it starts from the very first revision and runs the _selector against each version in turn. The sooner it finds a match, the sooner it returns a response. So in your case, you must have lots of revisions of documents that do not get selected by your selector. If you widen your selector to match all documents, you'll see that responses start coming much faster.

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