[GitHub] [beam] rezarokni commented on a change in pull request #12864: [BEAM-10650] Windmill implementation for TimestampOrderedState

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rezarokni commented on a change in pull request #12864:
URL: https://github.com/apache/beam/pull/12864#discussion_r492447897



##########
File path: runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/WindmillStateInternals.java
##########
@@ -470,81 +541,514 @@ protected WorkItemCommitRequest persistDirectly(WindmillStateCache.ForKey cache)
     }
   }
 
-  private static class WindmillOrderedList<T> extends SimpleWindmillState
-      implements OrderedListState<T> {
+  // Coder for closed-open ranges.
+  private static class RangeCoder<T extends Comparable> extends CustomCoder<Range<T>> {
+    private Coder<T> boundCoder;
+
+    RangeCoder(Coder<T> boundCoder) {
+      this.boundCoder = NullableCoder.of(boundCoder);
+    }
+
+    @Override
+    public void encode(Range<T> value, OutputStream outStream) throws CoderException, IOException {
+      Preconditions.checkState(
+          value.lowerBoundType().equals(BoundType.CLOSED), "unexpected range " + value);
+      Preconditions.checkState(
+          value.upperBoundType().equals(BoundType.OPEN), "unexpected range " + value);
+      boundCoder.encode(value.hasLowerBound() ? value.lowerEndpoint() : null, outStream);
+      boundCoder.encode(value.hasUpperBound() ? value.upperEndpoint() : null, outStream);
+    }
+
+    @Override
+    public Range<T> decode(InputStream inStream) throws CoderException, IOException {
+      @Nullable T lower = boundCoder.decode(inStream);
+      @Nullable T upper = boundCoder.decode(inStream);
+      if (lower == null) {
+        return upper != null ? Range.lessThan(upper) : Range.all();
+      } else if (upper == null) {
+        return Range.atLeast(lower);
+      } else {
+        return Range.closedOpen(lower, upper);
+      }
+    }
+  }
+
+  private static class RangeSetCoder<T extends Comparable> extends CustomCoder<RangeSet<T>> {
+    private SetCoder<Range<T>> rangesCoder;
+
+    RangeSetCoder(Coder<T> boundCoder) {
+      this.rangesCoder = SetCoder.of(new RangeCoder<>(boundCoder));
+    }
+
+    @Override
+    public void encode(RangeSet<T> value, OutputStream outStream) throws IOException {
+      rangesCoder.encode(value.asRanges(), outStream);
+    }
+
+    @Override
+    public RangeSet<T> decode(InputStream inStream) throws CoderException, IOException {
+      return TreeRangeSet.create(rangesCoder.decode(inStream));
+    }
+  }
+
+  /**
+   * Tracker for the ids used in an ordered list.
+   *
+   * <p>Windmill accepts an int64 id for each timestamped-element in the list. Unique elements are
+   * identified by the pair of timestamp and id. This means that tow unique elements e1, e2 must

Review comment:
       ```suggestion
      * identified by the pair of timestamp and id. This means that two unique elements e1, e2 must
   ```




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