Hi folks- I've got what I suspect is a fairly uncommon use-case, but I wanted to reach out to this group to see if it resonates with anyone else. I'll avoid going into all the details for now to keep this email terse and to the point, but I'm happy to elaborate further on the use-case if helpful.
Does anyone have a use-case for an "index or nothing" query that behaves similarly to IndexOrDocValuesQuery but has a no-op query as the doc-values query (i.e., MatchAllDocsQuery)? We have a fairly common use-case in Amazon's Product Search engine where we want to optionally—based on query heuristics—add a numeric range query, using the points index, to the first-phase execution. We don't ever want to add a doc values-based approximation though. Essentially, we have this separate way of doing more costly post-filtering that we don't directly model as a single doc values-based query. In cases where our numeric range approximation is very selective, we'd like to add a points-based index query to the approximation phase to help narrow down candidates, but in cases where our numeric range is not very selective (relative to the rest of the query), we'd like to skip using an approximation clause altogether. We used to use IndexOrDocValuesQuery for this with a MatchAllDocsQuery provided as the doc values-based query, but the behavior changed in Lucene 9.1 (GH#715 <https://github.com/apache/lucene/pull/715>) to rewrite the query into a MatchAllDocsQuery if either provided query were MatchAllDocs, which kills our ability to do this. I understand why we would assume that the both queries provided to IndexOrDocValuesQuery are functionally equivalent (and rewrite if either is MatchAllDocs), but it leads us down a path of implementing something similar but with a well-understood MatchAllDocs fallback behavior. I'm guessing the answer is "no," but does anyone have a similar use-case to this? Would there be any interest in an IndexOrNothingQuery (maybe in sandbox)? Does anyone have other use-cases for IndexOrDocValuesQuery where the two provided queries are _not_ functionally equivalent by design? Cheers, -Greg
