From 60d198327048be0f83b9a0d5d029912e6ac80da9 Mon Sep 17 00:00:00 2001
From: zhejiangxiaomai <zhenhui.zhao@intel.com>
Date: Tue, 5 Jul 2022 12:18:41 +0800
Subject: [PATCH] When only groupings exist, set the phase to be Single.

---
 velox/substrait/SubstraitToVeloxPlan.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/velox/substrait/SubstraitToVeloxPlan.cpp b/velox/substrait/SubstraitToVeloxPlan.cpp
index 1d6dc2a2e441..aafc2b998eb2 100644
--- a/velox/substrait/SubstraitToVeloxPlan.cpp
+++ b/velox/substrait/SubstraitToVeloxPlan.cpp
@@ -822,6 +822,11 @@ std::string SubstraitVeloxPlanConverter::findFuncSpec(uint64_t id) {
 bool SubstraitVeloxPlanConverter::needsRowConstruct(
     const ::substrait::AggregateRel& sAgg,
     core::AggregationNode::Step& aggStep) {
+  if (sAgg.measures().size() == 0) {
+    // When only groupings exist, set the phase to be Single.
+    aggStep = core::AggregationNode::Step::kSingle;
+    return false;
+  }
   for (const auto& smea : sAgg.measures()) {
     auto aggFunction = smea.measure();
     std::string funcName = subParser_->findVeloxFunction(