[GitHub] [lucene] jainankitk commented on issue #12297: Unnecessary BM25Scorer allocations for non-scoring queries

["jainankitk (via GitHub)" <gi...@apache.org>]

jainankitk commented on issue #12297:
URL: https://github.com/apache/lucene/issues/12297#issuecomment-1548859574

   I also came across [this discussion](https://lists.apache.org/thread/nrlkswkqh1bp80owb9yd9zzotcz81soj). Maybe I am missing some context, but could not understand why this is not an issue. Seems like regression to me, for specific customer use case. I also tried quick hack patch (always returning non-scoring similarity) just to confirm, and the float[] did not appear in the histogram / heap dump anymore.
   
   ```
    public class IndexSearcher {
    
   +  /** A search-time {@link Similarity} that does not make use of scoring factors
   +   *  and may be used when scores are not needed. */
   +  private static final Similarity NON_SCORING_SIMILARITY = new Similarity() {
   + 
   +    @Override
   +    public long computeNorm(FieldInvertState state) {
   +      throw new UnsupportedOperationException("This Similarity may only be used for searching, not indexing");
   +    }
   + 
   +    @Override
   +    public SimScorer scorer(float boost, CollectionStatistics collectionStats, TermStatistics... termStats) {
   +      return new SimScorer() {
   +        @Override
   +        public float score(float freq, long norm) {
   +          return 0f;
   +        }
   +      };
   +    }
   + 
   +  };
   +
      private static QueryCache DEFAULT_QUERY_CACHE;
      private static QueryCachingPolicy DEFAULT_CACHING_POLICY = new UsageTrackingQueryCachingPolicy();
      static {
   @@ -314,7 +336,7 @@ public class IndexSearcher {
       *  {@link Similarity} that has been set through {@link #setSimilarity(Similarity)}
       *  or the default {@link Similarity} if none has been set explicitly. */
      public Similarity getSimilarity() {
   -    return similarity;
   +    return NON_SCORING_SIMILARITY;
      }
    
      /**
   ```
   
   @jpountz - Can you check once and confirm if I am missing something?


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