From 29c2bca4649317f2ebb1c89f92bf97fbb27602ca Mon Sep 17 00:00:00 2001
From: Thomas Groh <tgroh@google.com>
Date: Wed, 5 Jul 2017 14:16:50 -0700
Subject: [PATCH] Disallow Combiner Lifting for multi-window WindowFns

---
 .../apache/beam/runners/dataflow/DataflowPipelineTranslator.java | 1 +
 1 file changed, 1 insertion(+)

diff --git a/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowPipelineTranslator.java b/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowPipelineTranslator.java
index 28fd1bb1af02..f1783def5040 100644
--- a/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowPipelineTranslator.java
+++ b/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowPipelineTranslator.java
@@ -793,6 +793,7 @@ private <K, V> void groupByKeyHelper(
                 context.getPipelineOptions().as(StreamingOptions.class).isStreaming();
             boolean disallowCombinerLifting =
                 !windowingStrategy.getWindowFn().isNonMerging()
+                    || !windowingStrategy.getWindowFn().assignsToOneWindow()
                     || (isStreaming && !transform.fewKeys())
                     // TODO: Allow combiner lifting on the non-default trigger, as appropriate.
                     || !(windowingStrategy.getTrigger() instanceof DefaultTrigger);