[GitHub] [lucene-solr] s1monw commented on a change in pull request #688: LUCENE-8813: Ensure we never apply deletes from a closed DWPTDeleteQueue

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

s1monw commented on a change in pull request #688: LUCENE-8813: Ensure we never apply deletes from a closed DWPTDeleteQueue
URL: https://github.com/apache/lucene-solr/pull/688#discussion_r288699573
 
 

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 File path: lucene/core/src/java/org/apache/lucene/index/DocumentsWriter.java
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 @@ -168,27 +168,28 @@ long updateDocValues(DocValuesUpdate... updates) throws IOException {
   }
 
   private synchronized long applyDeleteOrUpdate(ToLongFunction<DocumentsWriterDeleteQueue> function) throws IOException {
-    // TODO why is this synchronized?
+    // This method is synchronized to make sure we don't replace the deleteQueue while applying this update / delete
+    // otherwise we might loose an update / delete if this happens concurrently to a full flush.
     final DocumentsWriterDeleteQueue deleteQueue = this.deleteQueue;
     long seqNo = function.applyAsLong(deleteQueue);
     flushControl.doOnDelete();
     lastSeqNo = Math.max(lastSeqNo, seqNo);
-    if (applyAllDeletes(deleteQueue)) {
+    if (applyAllDeletes()) {
       seqNo = -seqNo;
     }
     return seqNo;
   }
   
   /** If buffered deletes are using too much heap, resolve them and write disk and return true. */
-  private boolean applyAllDeletes(DocumentsWriterDeleteQueue deleteQueue) throws IOException {
+  private boolean applyAllDeletes() throws IOException {
+    final DocumentsWriterDeleteQueue deleteQueue = this.deleteQueue;
     if (flushControl.isFullFlush() == false // never apply deletes during full flush this breaks happens before relationship
+        && deleteQueue.isOpen() // if it's closed then it's already fully applied and we have a new delete queue
         && flushControl.getAndResetApplyAllDeletes()) {
-      if (deleteQueue != null) {
 
 Review comment:
   yeah it can't be null afaik

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