support limit in agg exec for ser/deser

datafusion/proto/proto/datafusion.proto

@@ -1110,6 +1110,11 @@ message MaybePhysicalSortExprs {
   repeated PhysicalSortExprNode sort_expr = 1;
 }
 
+message AggLimit {
+  // wrap into a message to make it optional
+  uint64 limit = 1;
+}
+
 message AggregateExecNode {
   repeated PhysicalExprNode group_expr = 1;
   repeated PhysicalExprNode aggr_expr = 2;
@@ -1122,6 +1127,7 @@ message AggregateExecNode {
   repeated PhysicalExprNode null_expr = 8;
   repeated bool groups = 9;
   repeated MaybeFilter filter_expr = 10;
+  AggLimit limit = 11;
 }
 
 message GlobalLimitExecNode {

datafusion/proto/src/physical_plan/mod.rs

@@ -539,14 +539,23 @@ impl AsExecutionPlan for protobuf::PhysicalPlanNode {
                     })
                     .collect::<Result<Vec<_>, _>>()?;
 
-                Ok(Arc::new(AggregateExec::try_new(
+                let limit = hash_agg
+                    .limit
+                    .as_ref()
+                    .map(|lit_value| lit_value.limit as usize);
+
+                let agg = AggregateExec::try_new(
                     agg_mode,
                     PhysicalGroupBy::new(group_expr, null_expr, groups),
                     physical_aggr_expr,
                     physical_filter_expr,
                     input,
                     physical_schema,
-                )?))
+                )?;
+
+                let agg = agg.with_limit(limit);
+
+                Ok(Arc::new(agg))
             }
             PhysicalPlanType::HashJoin(hashjoin) => {
                 let left: Arc<dyn ExecutionPlan> = into_physical_plan(
@@ -1504,6 +1513,10 @@ impl AsExecutionPlan for protobuf::PhysicalPlanNode {
                 .map(|expr| serialize_physical_expr(expr.0.to_owned(), extension_codec))
                 .collect::<Result<Vec<_>>>()?;
 
+            let limit = exec.limit().map(|value| protobuf::AggLimit {
+                limit: value as u64,
+            });
+
             return Ok(protobuf::PhysicalPlanNode {
                 physical_plan_type: Some(PhysicalPlanType::Aggregate(Box::new(
                     protobuf::AggregateExecNode {
@@ -1517,6 +1530,7 @@ impl AsExecutionPlan for protobuf::PhysicalPlanNode {
                         input_schema: Some(input_schema.as_ref().try_into()?),
                         null_expr,
                         groups,
+                        limit,
                     },
                 ))),
             });

datafusion/proto/tests/cases/roundtrip_physical_plan.rs

@@ -370,6 +370,33 @@ fn rountrip_aggregate() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn rountrip_aggregate_with_limit() -> Result<()> {
+    let field_a = Field::new("a", DataType::Int64, false);
+    let field_b = Field::new("b", DataType::Int64, false);
+    let schema = Arc::new(Schema::new(vec![field_a, field_b]));
+
+    let groups: Vec<(Arc<dyn PhysicalExpr>, String)> =
+        vec![(col("a", &schema)?, "unused".to_string())];
+
+    let aggregates: Vec<Arc<dyn AggregateExpr>> = vec![Arc::new(Avg::new(
+        cast(col("b", &schema)?, &schema, DataType::Float64)?,
+        "AVG(b)".to_string(),
+        DataType::Float64,
+    ))];
+
+    let agg = AggregateExec::try_new(
+        AggregateMode::Final,
+        PhysicalGroupBy::new_single(groups.clone()),
+        aggregates.clone(),
+        vec![None],
+        Arc::new(EmptyExec::new(schema.clone())),
+        schema,
+    )?;
+    let agg = agg.with_limit(Some(12));
+    roundtrip_test(Arc::new(agg))
+}
+
 #[test]
 fn roundtrip_aggregate_udaf() -> Result<()> {
     let field_a = Field::new("a", DataType::Int64, false);