[GitHub] [lucene] zhaih commented on a change in pull request #157: LUCENE-9963 Fix issue with FlattenGraphFilter throwing exceptions from holes

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

zhaih commented on a change in pull request #157:
URL: https://github.com/apache/lucene/pull/157#discussion_r642115419



##########
File path: lucene/analysis/common/src/java/org/apache/lucene/analysis/core/FlattenGraphFilter.java
##########
@@ -193,14 +194,25 @@ private boolean releaseBufferedToken() {
         }
         if (inputNode.tokens.size() == 0) {
           assert inputNode.nextOut == 0;
-          assert output.nextOut == 0;
           // Hole dest nodes should never be merged since 1) we always
           // assign them to a new output position, and 2) since they never
           // have arriving tokens they cannot be pushed:
-          assert output.inputNodes.size() == 1 : output.inputNodes.size();
+          // skip hole sources, but don't free until every input is checked
+          if (output.inputNodes.size() > 1) {
+            output.inputNodes.remove(output.nextOut);
+            if (output.nextOut < output.inputNodes.size()) {
+              continue;
+            }
+          }
+
           outputFrom++;
-          inputNodes.freeBefore(output.inputNodes.get(0));
+          int freeBefore = Collections.min(output.inputNodes);
+          assert outputNodes.get(outputFrom).inputNodes.stream().filter(n -> freeBefore < n).count()

Review comment:
       I'm a bit confused about this assertion. Are we trying to assert no future node will be freed mistakenly? If that's the case, shouldn't we assert:
   ```
   assert outputNodes.get(outputFrom).inputNodes.stream().filter(n -> freeBefore > n).count() == 0
       : "FreeBefore " + freeBefore + " will free in use nodes"
   ```




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