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

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madrob commented on a change in pull request #180:
URL: https://github.com/apache/lucene/pull/180#discussion_r654162699



##########
File path: lucene/core/src/java/org/apache/lucene/index/IndexReader.java
##########
@@ -307,8 +307,21 @@ public final int hashCode() {
   /**
    * Retrieve term vectors for this document, or null if term vectors were not indexed. The returned
    * Fields instance acts like a single-document inverted index (the docID will be 0).
+   *
+   * @deprecated Use {@link IndexReader#getTermVectorsReader} instead.
    */
-  public abstract Fields getTermVectors(int docID) throws IOException;
+  @Deprecated
+  public final Fields getTermVectors(int docID) throws IOException {
+    TermVectors termVectors = getTermVectorsReader();
+    if (termVectors != null) {
+      return termVectors.get(docID);
+    }
+    return null;
+  }
+  ;
+
+  /** Get TermVectors from this index, or null if term vectors were not indexed. */
+  public abstract TermVectors getTermVectorsReader();

Review comment:
       This naming feels weird to me that it returns TV not TVR.

##########
File path: lucene/core/src/java/org/apache/lucene/index/TermVectors.java
##########
@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.index;
+
+import java.io.IOException;
+import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
+
+/** Index API to access TermVectors */
+public abstract class TermVectors {

Review comment:
       This should probably be an interface?

##########
File path: lucene/core/src/java/org/apache/lucene/index/BaseCompositeReader.java
##########
@@ -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'm not sure why but this scares me a little bit. Feels like there's a potential for more garbage than we currently get on the heap. I haven't measured anything though, so maybe it's ok?

##########
File path: lucene/core/src/java/org/apache/lucene/index/TermVectors.java
##########
@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.index;
+
+import java.io.IOException;
+import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
+
+/** Index API to access TermVectors */
+public abstract class TermVectors {

Review comment:
       I’m really curious about the disadvantages you see with an interface versus an class with every method abstract. Can you give some hints so that I can do further research?




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