From aa5081efcf34a566df2d6a6d2bf163dc68941551 Mon Sep 17 00:00:00 2001
From: TengJianPing <tengjianping@selectdb.com>
Date: Thu, 11 Jun 2026 14:37:42 +0800
Subject: [PATCH] [fix](be) Return NaN for avg_weighted when sum of weights is
 zero (#64333)

Problem Summary: When the sum of weights passed to avg_weighted is zero
but the weighted data sum is non-zero, the function computed data_sum /
weight_sum and returned +/-Infinity (e.g. avg_weighted(f1, f2) over rows
(1, 1), (2, -1) returned -Infinity). The expected mathematical result of
a division by zero weight is undefined, so it should return NaN.

This fixes AggregateFunctionAvgWeightedData::get() to return quiet_NaN()
when weight_sum is exactly zero, instead of producing Infinity.
---
 .../aggregate/aggregate_function_avg_weighted.h    |  8 +++++++-
 .../support_type/avg_weighted/avg_weighted.out     |  3 +++
 .../support_type/avg_weighted/avg_weighted.groovy  | 14 ++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/be/src/exprs/aggregate/aggregate_function_avg_weighted.h b/be/src/exprs/aggregate/aggregate_function_avg_weighted.h
index 75643457d96f2e..261d068e7463ae 100644
--- a/be/src/exprs/aggregate/aggregate_function_avg_weighted.h
+++ b/be/src/exprs/aggregate/aggregate_function_avg_weighted.h
@@ -22,6 +22,7 @@
 #include <algorithm>
 #include <boost/iterator/iterator_facade.hpp>
 #include <cmath>
+#include <limits>
 #include <memory>
 #include <type_traits>
 
@@ -77,7 +78,12 @@ struct AggregateFunctionAvgWeightedData {
         weight_sum = 0.0;
     }
 
-    double get() const { return data_sum / weight_sum; }
+    double get() const {
+        if (weight_sum == 0.0) {
+            return std::numeric_limits<double>::quiet_NaN();
+        }
+        return data_sum / weight_sum;
+    }
 
     double data_sum = 0.0;
     double weight_sum = 0.0;
diff --git a/regression-test/data/query_p0/aggregate/support_type/avg_weighted/avg_weighted.out b/regression-test/data/query_p0/aggregate/support_type/avg_weighted/avg_weighted.out
index f7365ee6724c96..dd8b4f7056b32a 100644
--- a/regression-test/data/query_p0/aggregate/support_type/avg_weighted/avg_weighted.out
+++ b/regression-test/data/query_p0/aggregate/support_type/avg_weighted/avg_weighted.out
@@ -2,3 +2,6 @@
 -- !sql_double --
 2.718281828
 
+-- !sql_zero_weight --
+NaN
+
diff --git a/regression-test/suites/query_p0/aggregate/support_type/avg_weighted/avg_weighted.groovy b/regression-test/suites/query_p0/aggregate/support_type/avg_weighted/avg_weighted.groovy
index f49adef5d8ce7e..755adb4119694c 100644
--- a/regression-test/suites/query_p0/aggregate/support_type/avg_weighted/avg_weighted.groovy
+++ b/regression-test/suites/query_p0/aggregate/support_type/avg_weighted/avg_weighted.groovy
@@ -43,4 +43,18 @@ suite("avg_weighted") {
     """
     
     qt_sql_double """select avg_weighted(col_double, weight_double) from d_table;"""
+
+    // weight sum is zero, should return NaN instead of +/-Infinity
+    sql """
+        drop table if exists test_avg_weighted_zero;
+    """
+    sql """
+        create table test_avg_weighted_zero (f1 int, f2 int)
+        distributed BY hash(f1) buckets 1
+        properties("replication_num" = "1");
+    """
+    sql """
+        insert into test_avg_weighted_zero values (1, 1), (2, -1);
+    """
+    qt_sql_zero_weight """select avg_weighted(f1, f2) from test_avg_weighted_zero;"""
 }
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