feat(frontend): add stateless two-phase ApproxPercentile

proto/expr.proto

@@ -436,6 +436,8 @@ message AggCall {
     LAST_VALUE = 25;
     GROUPING = 26;
     INTERNAL_LAST_SEEN_VALUE = 27;
+    APPROX_PERCENTILE = 28;
+
     // user defined aggregate function
     USER_DEFINED = 100;
     // wraps a scalar function that takes a list as input as an aggregate function.

src/expr/core/src/aggregate/def.rs

@@ -313,7 +313,10 @@ pub mod agg_kinds {
                     | PbAggKind::StddevSamp
                     | PbAggKind::VarPop
                     | PbAggKind::VarSamp
-                    | PbAggKind::Grouping,
+                    | PbAggKind::Grouping
+                    // ApproxPercentile always uses custom agg executors,
+                    // rather than an aggregation operator
+                    | PbAggKind::ApproxPercentile
             )
         };
     }
@@ -443,7 +446,10 @@ pub mod agg_kinds {
     macro_rules! ordered_set {
         () => {
             AggKind::Builtin(
-                PbAggKind::PercentileCont | PbAggKind::PercentileDisc | PbAggKind::Mode,
+                PbAggKind::PercentileCont
+                    | PbAggKind::PercentileDisc
+                    | PbAggKind::Mode
+                    | PbAggKind::ApproxPercentile,
             )
         };
     }

src/expr/impl/src/aggregate/approx_percentile.rs

@@ -0,0 +1,67 @@
+// Copyright 2024 RisingWave Labs
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::ops::Range;
+
+use risingwave_common::array::*;
+use risingwave_common::types::*;
+use risingwave_common_estimate_size::EstimateSize;
+use risingwave_expr::aggregate::{AggCall, AggStateDyn, AggregateFunction, AggregateState};
+use risingwave_expr::{build_aggregate, Result};
+
+#[build_aggregate("approx_percentile(float8) -> float8")]
+fn build(agg: &AggCall) -> Result<Box<dyn AggregateFunction>> {
+    let fraction = agg.direct_args[0]
+        .literal()
+        .map(|x| (*x.as_float64()).into());
+    Ok(Box::new(ApproxPercentile { fraction }))
+}
+
+#[allow(dead_code)]
+pub struct ApproxPercentile {
+    fraction: Option<f64>,
+}
+
+#[derive(Debug, Default, EstimateSize)]
+struct State(Vec<f64>);
+
+impl AggStateDyn for State {}
+
+#[async_trait::async_trait]
+impl AggregateFunction for ApproxPercentile {
+    fn return_type(&self) -> DataType {
+        DataType::Float64
+    }
+
+    fn create_state(&self) -> Result<AggregateState> {
+        todo!()
+    }
+
+    async fn update(&self, _state: &mut AggregateState, _input: &StreamChunk) -> Result<()> {
+        todo!()
+    }
+
+    async fn update_range(
+        &self,
+        _state: &mut AggregateState,
+        _input: &StreamChunk,
+        _range: Range<usize>,
+    ) -> Result<()> {
+        todo!()
+    }
+
+    async fn get_result(&self, _state: &AggregateState) -> Result<Datum> {
+        todo!()
+    }
+}

src/expr/impl/src/aggregate/mod.rs

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 mod approx_count_distinct;
+mod approx_percentile;
 mod array_agg;
 mod bit_and;
 mod bit_or;

src/frontend/planner_test/tests/testdata/input/agg.yaml

@@ -1000,3 +1000,59 @@
   expected_outputs:
     - batch_plan
     - stream_plan
+- name: test duplicate agg
+  sql: |
+    CREATE TABLE t (v1 int);
+    SELECT sum(v1) as x, count(v1) as y, sum(v1) as z, count(v1) as w from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile alone
+  sql: |
+    CREATE TABLE t (v1 int);
+    SELECT approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1) from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with other simple aggs
+  sql: |
+    CREATE TABLE t (v1 int);
+    SELECT approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1), sum(v1) from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with other simple aggs (sum, count)
+  sql: |
+    CREATE TABLE t (v1 int);
+    SELECT sum(v1) as s1, approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1), sum(v1) as s2, count(v1) from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with duplicate approx_percentile
+  sql: |
+    CREATE TABLE t (v1 int);
+    SELECT approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1) as x, approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1) as y from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with different approx_percentile
+  sql: |
+    CREATE TABLE t (v1 int, v2 int);
+    SELECT approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1) as x, approx_percentile(0.5, 0.01) WITHIN GROUP (order by v2) as y from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with different approx_percentile interleaved with stateless simple aggs
+  sql: |
+    CREATE TABLE t (v1 int, v2 int);
+    SELECT sum(v1) as s1, approx_percentile(0.5, 0.01) WITHIN GROUP (order by v1) as x, count(*), sum(v2) as s2, approx_percentile(0.5, 0.01) WITHIN GROUP (order by v2) as y from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan
+- name: test simple approx_percentile with descending order
+  sql: |
+    CREATE TABLE t (v1 int, v2 int);
+    SELECT sum(v1) as s1, approx_percentile(0.2, 0.01) WITHIN GROUP (order by v1 desc) from t;
+  expected_outputs:
+    - logical_plan
+    - stream_plan