jhnmora000 commented on a change in pull request #12313:
URL: https://github.com/apache/beam/pull/12313#discussion_r458402011
##########
File path:
sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/transform/BeamBuiltinAnalyticFunctions.java
##########
@@ -42,4 +44,77 @@
throw new UnsupportedOperationException(
String.format("Analytics Function [%s] is not supported",
functionName));
}
+
+ public static <T> Combine.CombineFn<T, ?, T> navigationFirstValue() {
+ return new FirstValueCombineFn();
+ }
+
+ public static <T> Combine.CombineFn<T, ?, T> navigationLastValue() {
+ return new LastValueCombineFn();
+ }
+
+ private static class FirstValueCombineFn<T> extends Combine.CombineFn<T,
Optional<T>, T> {
+ private FirstValueCombineFn() {}
+
+ @Override
+ public Optional<T> createAccumulator() {
+ return Optional.empty();
+ }
+
+ @Override
+ public Optional<T> addInput(Optional<T> accumulator, T input) {
+ Optional<T> r = accumulator;
+ if (!accumulator.isPresent()) {
+ r = Optional.of(input);
+ }
+ return r;
+ }
+
+ @Override
+ public Optional<T> mergeAccumulators(Iterable<Optional<T>> accumulators) {
+ Optional<T> r = Optional.empty();
+ for (Optional<T> ac : accumulators) {
+ if (!r.isPresent() && ac.isPresent()) {
+ r = ac;
Review comment:
Since, navigation functions rely on a sorted input and the addInput
method actually should be called synchronously, the mergeAccumulators method
never is invoked. So, I was wondering If I would rather remove this code and
leave a mock implementation (let's say return null). What do you think?
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