[GitHub] [lucene] jpountz commented on a change in pull request #242: LUCENE-9620 Add Weight#count(LeafReaderContext)

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

jpountz commented on a change in pull request #242:
URL: https://github.com/apache/lucene/pull/242#discussion_r699205142



##########
File path: lucene/core/src/java/org/apache/lucene/search/FilterWeight.java
##########
@@ -67,4 +67,9 @@ public Scorer scorer(LeafReaderContext context) throws IOException {
   public Matches matches(LeafReaderContext context, int doc) throws IOException {
     return in.matches(context, doc);
   }
+
+  @Override
+  public int count(LeafReaderContext context) throws IOException {
+    return in.count(context);
+  }

Review comment:
       In general we only forward calls to the wrapped instance in `FilterXXX` classes when the method is abstract. This is why `FilterWeight` doesn't implement `bulkScorer` for instance.
   
   The reason why we do this is because it can be a bit trappy otherwise, e.g. someone extends FilterWeight and overrides the `scorer()` method but forgets to override `count`.
   
   We should move this to the concrete instances where it's correct to forward to the wrapped instance like the Weight of `ConstantScoreQuery`.

##########
File path: lucene/core/src/java/org/apache/lucene/search/TermQuery.java
##########
@@ -179,6 +179,22 @@ public Explanation explain(LeafReaderContext context, int doc) throws IOExceptio
       }
       return Explanation.noMatch("no matching term");
     }
+
+    @Override
+    public int count(LeafReaderContext context) throws IOException {
+      if (context.reader().hasDeletions() == false) {
+        TermsEnum termsEnum = getTermsEnum(context);
+        // termsEnum is not null if term state is available
+        if (termsEnum != null) {
+          return termsEnum.docFreq();
+        } else {
+          // no term state found so rely on the default reader.docFreq call
+          return context.reader().docFreq(term);

Review comment:
       You could return `0` directly here, if `getTermsEnum` returns `null` , it means that the term cannot be found in the dictionary, so the count for the query is 0.




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