[GitHub] [beam] steveniemitz commented on a change in pull request #11823: [BEAM-7568] Avoid re-encoding value state cells each commit

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

steveniemitz commented on a change in pull request #11823:
URL: https://github.com/apache/beam/pull/11823#discussion_r430837481



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File path: runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillStateInternals.java
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@@ -410,14 +416,18 @@ protected WorkItemCommitRequest persistDirectly(WindmillStateCache.ForKey cache)
         return WorkItemCommitRequest.newBuilder().buildPartial();
       }
 
-      ByteString.Output stream = ByteString.newOutput();
-      if (value != null) {
-        coder.encode(value, stream, Coder.Context.OUTER);
+      ByteString encoded = null;
+      if (cachedSize == -1 || modified) {

Review comment:
       agreed, it took me awhile to reason this out w/ the different code paths that can affect the values here.  I'm reasonably sure you don't need the `cachedSize == -1` branch but, it's been working like this for ~1 year so I didn't want to tempt fate.
   
   There's also the case where this is the first write, but `valueIsKnown = false` (because `isNewKey = false`), so we end up with a read that doesn't return anything.
   
   Thanks for the quick reviews!




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