[GitHub] [lucene] zacharymorn commented on a change in pull request #180: LUCENE-9959: Add non thread local based API for term vector reader usage

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

zacharymorn commented on a change in pull request #180:
URL: https://github.com/apache/lucene/pull/180#discussion_r661242673



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File path: lucene/core/src/java/org/apache/lucene/index/BaseCompositeReader.java
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@@ -112,10 +112,29 @@ protected BaseCompositeReader(R[] subReaders, Comparator<R> subReadersSorter) th
   }
 
   @Override
-  public final Fields getTermVectors(int docID) throws IOException {
-    ensureOpen();
-    final int i = readerIndex(docID); // find subreader num
-    return subReaders[i].getTermVectors(docID - starts[i]); // dispatch to subreader
+  public final TermVectors getTermVectorsReader() {
+    TermVectors[] termVectors = new TermVectors[subReaders.length];
+
+    // subReaders is a collection of segmentReaders
+    for (int i = 0; i < subReaders.length; i++) {
+      // the getTermVectorsReader would clone a new instance, hence saving it into an array
+      // to avoid re-cloning from direct subReaders[i].getTermVectorsReader() call
+      termVectors[i] = subReaders[i].getTermVectorsReader();
+    }
+
+    return new TermVectors() {

Review comment:
       I've implemented the lazy-init approach in the latest commit and it passed the existing tests (in particular, `TestMultiThreadTermVectors`), so I think it should be safe for threaded situation? One downside from this approach I see though is that since `null` was used to indicate both TV not available and not initialized, lazy-init will require repeated `subReaders[i].getTermVectorsReader()` calls to get TV reader in the same segment if that segment simply doesn't contain any TV index.




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