diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalAggregate.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalAggregate.java
index 75f9790accbf5f..562a5868ec85fe 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalAggregate.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalAggregate.java
@@ -29,8 +29,6 @@
import org.apache.doris.nereids.trees.expressions.functions.ExpressionTrait;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregatePhase;
-import org.apache.doris.nereids.trees.expressions.functions.agg.Count;
-import org.apache.doris.nereids.trees.expressions.functions.agg.Ndv;
import org.apache.doris.nereids.trees.expressions.literal.Literal;
import org.apache.doris.nereids.trees.plans.Plan;
import org.apache.doris.nereids.trees.plans.PlanType;
@@ -446,7 +444,7 @@ private boolean isUniformGroupByUnique(NamedExpression namedExpression) {
return false;
}
Expression agg = namedExpression.child(0);
- return agg instanceof Count || agg instanceof Ndv;
+ return ExpressionUtils.isUniformAgg(agg);
}
@Override
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/physical/PhysicalHashAggregate.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/physical/PhysicalHashAggregate.java
index 56f0f77875226d..80a08df4495f54 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/physical/PhysicalHashAggregate.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/physical/PhysicalHashAggregate.java
@@ -29,8 +29,6 @@
import org.apache.doris.nereids.trees.expressions.Slot;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;
import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateParam;
-import org.apache.doris.nereids.trees.expressions.functions.agg.Count;
-import org.apache.doris.nereids.trees.expressions.functions.agg.Ndv;
import org.apache.doris.nereids.trees.expressions.functions.agg.NullableAggregateFunction;
import org.apache.doris.nereids.trees.plans.AggMode;
import org.apache.doris.nereids.trees.plans.AggPhase;
@@ -407,7 +405,7 @@ private boolean isUniformGroupByUnique(NamedExpression namedExpression) {
return false;
}
Expression agg = namedExpression.child(0);
- return agg instanceof Count || agg instanceof Ndv;
+ return ExpressionUtils.isUniformAgg(agg);
}
@Override
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/util/ExpressionUtils.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/util/ExpressionUtils.java
index 6ab9695c1ca59a..836db942c18ddf 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/util/ExpressionUtils.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/util/ExpressionUtils.java
@@ -55,8 +55,10 @@
import org.apache.doris.nereids.trees.expressions.functions.BoundFunction;
import org.apache.doris.nereids.trees.expressions.functions.NoneMovableFunction;
import org.apache.doris.nereids.trees.expressions.functions.agg.Avg;
+import org.apache.doris.nereids.trees.expressions.functions.agg.Count;
import org.apache.doris.nereids.trees.expressions.functions.agg.Max;
import org.apache.doris.nereids.trees.expressions.functions.agg.Min;
+import org.apache.doris.nereids.trees.expressions.functions.agg.Ndv;
import org.apache.doris.nereids.trees.expressions.functions.agg.Sum;
import org.apache.doris.nereids.trees.expressions.functions.generator.Explode;
import org.apache.doris.nereids.trees.expressions.functions.generator.ExplodeBitmap;
@@ -1186,6 +1188,24 @@ public static boolean isInjectiveAgg(Expression agg) {
return agg instanceof Sum || agg instanceof Avg || agg instanceof Max || agg instanceof Min;
}
+ /**
+ * Whether a single-row group always produces the same aggregate result.
+ *
+ * COUNT(*) always consumes its only row. Argument-based COUNT and NDV consume the row only
+ * when every argument is non-null, so nullable arguments may produce either zero or one across
+ * otherwise single-row groups. Keep the proof conservative and inspect the complete argument
+ * expressions rather than only their input slots.
+ */
+ public static boolean isUniformAgg(Expression agg) {
+ if (agg instanceof Count && ((Count) agg).isCountStar()) {
+ return true;
+ }
+ if (!(agg instanceof Count || agg instanceof Ndv)) {
+ return false;
+ }
+ return agg.getArguments().stream().allMatch(Expression::notNullable);
+ }
+
public static Set mutableCollect(List expressions,
Predicate> predicate) {
Set set = new HashSet<>();
diff --git a/fe/fe-core/src/test/java/org/apache/doris/nereids/properties/UniformTest.java b/fe/fe-core/src/test/java/org/apache/doris/nereids/properties/UniformTest.java
index 77395258281a9a..4349b2e7a2eec3 100644
--- a/fe/fe-core/src/test/java/org/apache/doris/nereids/properties/UniformTest.java
+++ b/fe/fe-core/src/test/java/org/apache/doris/nereids/properties/UniformTest.java
@@ -45,6 +45,13 @@ protected void runBeforeAll() throws Exception {
+ "UNIQUE KEY(id)\n"
+ "distributed by hash(id) buckets 10\n"
+ "properties('replication_num' = '1');");
+ createTable("create table test.uniform_agg_witness (\n"
+ + "pk int not null,\n"
+ + "b int not null,\n"
+ + "v int null)\n"
+ + "UNIQUE KEY(pk)\n"
+ + "distributed by hash(pk) buckets 10\n"
+ + "properties('replication_num' = '1');");
connectContext.setDatabase("test");
connectContext.getSessionVariable().setDisableNereidsRules("PRUNE_EMPTY_PARTITION");
}
@@ -79,6 +86,33 @@ void testAgg() {
}
+ @Test
+ void testSingleRowAggregateUniformityRequiresStableParticipation() {
+ assertAggregateUniform("select count(*) from uniform_agg_witness group by pk", true);
+ assertAggregateUniform("select count(b) from uniform_agg_witness group by pk", true);
+ assertAggregateUniform("select ndv(b) from uniform_agg_witness group by pk", true);
+ assertAggregateUniform("select count(distinct pk, b) from uniform_agg_witness group by pk", true);
+ assertAggregateUniform("select count(if(v is null, 1, 0)) from uniform_agg_witness group by pk", true);
+
+ assertAggregateUniform("select count(v) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform("select ndv(v) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform("select count(distinct b, v) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform(
+ "select count(if(v is null, 1, null)) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform("select count(cast(pk as tinyint)) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform("select count(try_cast(pk as tinyint)) from uniform_agg_witness group by pk", false);
+ assertAggregateUniform("select count(u.name) from uniform_agg_witness w "
+ + "left join uni u on w.pk = u.id group by w.pk", false);
+ }
+
+ private void assertAggregateUniform(String sql, boolean expected) {
+ Plan plan = PlanChecker.from(connectContext)
+ .analyze(sql)
+ .getPlan();
+ Assertions.assertEquals(expected, plan.getLogicalProperties().getTrait()
+ .isUniform(plan.getOutput().get(0)), sql);
+ }
+
@Test
void testTopNLimit() {
Plan plan = PlanChecker.from(connectContext)
diff --git a/regression-test/data/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.out b/regression-test/data/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.out
index 83fc7e067d92f4..16766b30675ec5 100644
--- a/regression-test/data/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.out
+++ b/regression-test/data/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.out
@@ -8,6 +8,21 @@
-- !tranform_to_scalar_agg_not_null_column --
+-- !nullable_count_not_uniform --
+7 0 1 0
+7 1 1 1
+
+-- !nullable_ndv_not_uniform --
+7 0 1 0
+7 1 1 1
+
+-- !multi_argument_count_not_uniform --
+7 0 1
+7 1 1
+
+-- !non_nullable_count_uniform --
+7 1 2
+
-- !project_const --
\N 1
\N 1
diff --git a/regression-test/suites/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.groovy b/regression-test/suites/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.groovy
index 4b5b63ead8f6d0..3d7bef31f1cd2b 100644
--- a/regression-test/suites/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.groovy
+++ b/regression-test/suites/nereids_rules_p0/eliminate_gby_key/eliminate_group_by_key_by_uniform.groovy
@@ -42,6 +42,97 @@ suite("eliminate_group_by_key_by_uniform") {
qt_empty_tranform_multi_column "select a, min(a), sum(a), count(a) from eli_gbk_by_uniform_t where a = 1 group by a, b,'abc' order by 1,2,3,4"
qt_tranform_to_scalar_agg_not_null_column "select b, min(a), sum(a), count(a) from eli_gbk_by_uniform_t where b = 1 group by a, b order by 1,2,3,4"
+ sql "drop table if exists uniform_agg_witness"
+ sql """
+ create table uniform_agg_witness (
+ pk int not null,
+ b int not null,
+ v int null
+ ) unique key(pk)
+ distributed by hash(pk) buckets 1
+ properties("replication_num"="1")
+ """
+ sql "insert into uniform_agg_witness values (1, 7, null), (2, 7, 9)"
+
+ def nullableCountPlan = sql("""
+ explain select b, c, count(*) as n, sum(h) as sh
+ from (
+ select pk, b, count(v) as c, ndv(v) as h
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, c
+ """).collect { it[0] }.join("\n")
+ assertTrue((nullableCountPlan =~ /group by: b\[#\d+\], c\[#\d+\]/).find(),
+ "nullable COUNT must remain in the outer group keys:\n${nullableCountPlan}")
+
+ def nullableNdvPlan = sql("""
+ explain select b, h, count(*) as n, sum(c) as sc
+ from (
+ select pk, b, count(v) as c, ndv(v) as h
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, h
+ """).collect { it[0] }.join("\n")
+ assertTrue((nullableNdvPlan =~ /group by: b\[#\d+\], h\[#\d+\]/).find(),
+ "nullable NDV must remain in the outer group keys:\n${nullableNdvPlan}")
+
+ def nonNullableCountPlan = sql("""
+ explain select b, c, count(*) as n
+ from (
+ select pk, b, count(b) as c
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, c
+ """).collect { it[0] }.join("\n")
+ assertTrue((nonNullableCountPlan =~ /group by: b\[#\d+\]/).find(),
+ "non-null COUNT should keep the safe group-key elimination:\n${nonNullableCountPlan}")
+ assertFalse((nonNullableCountPlan =~ /group by: b\[#\d+\], c\[#\d+\]/).find(),
+ "non-null COUNT should not remain in the outer group keys:\n${nonNullableCountPlan}")
+
+ order_qt_nullable_count_not_uniform """
+ select b, c, count(*) as n, sum(h) as sh
+ from (
+ select pk, b, count(v) as c, ndv(v) as h
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, c
+ order by b, c
+ """
+ order_qt_nullable_ndv_not_uniform """
+ select b, h, count(*) as n, sum(c) as sc
+ from (
+ select pk, b, count(v) as c, ndv(v) as h
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, h
+ order by b, h
+ """
+ order_qt_multi_argument_count_not_uniform """
+ select b, c, count(*) as n
+ from (
+ select pk, b, count(distinct b, v) as c
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, c
+ order by b, c
+ """
+ order_qt_non_nullable_count_uniform """
+ select b, c, count(*) as n
+ from (
+ select pk, b, count(b) as c
+ from uniform_agg_witness
+ group by pk, b
+ ) s
+ group by b, c
+ order by b, c
+ """
+
qt_project_const "select sum(c1), c2 from (select a c1,1 c2, d c3 from eli_gbk_by_uniform_t) t group by c2,c3 order by 1,2;"
qt_project_slot_uniform "select max(c3), c1,c2,c3 from (select a c1,1 c2, d c3 from eli_gbk_by_uniform_t where a=1) t group by c1,c2,c3 order by 1,2,3,4;"
@@ -332,4 +423,4 @@ GROUP BY
);
"""
-}
\ No newline at end of file
+}