[GitHub] [lucene] gsmiller commented on a diff in pull request #12003: Some minor code cleanup in IndexSortSortedNumericDocValuesRangeQuery

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

gsmiller commented on code in PR #12003:
URL: https://github.com/apache/lucene/pull/12003#discussion_r1044931897


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lucene/sandbox/src/java/org/apache/lucene/sandbox/search/IndexSortSortedNumericDocValuesRangeQuery.java:
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@@ -692,7 +697,7 @@ public int advance(int target) throws IOException {
 
     @Override
     public long cost() {
-      return lastDoc - firstDoc;
+      return Math.min(delegate.cost(), lastDoc - firstDoc);

Review Comment:
   Good question. So `delegate.cost()` will approximate the number of documents that could be provided in total by the delegate (in this case, it's `NumericDocValues`). `lastDoc - firstDoc` of course will provide the correct number of docs _if_ every doc has a value. In this case, `delegate` tells us what docs actually have values, and because we're using this, we know not all docs have values, so `lastDoc - firstDoc` _may_ overestimate. If the number of docs containing a value are very sparse though, it's possible we'll over-estimate by a lot, so providing a ceiling using `delegate.cost()` could be useful in certain cases. Hope that makes sense?



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