risingwave_expr/table_function/
empty.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use super::*;
16
17/// An empty table function that returns nothing.
18pub fn empty(return_type: DataType) -> BoxedTableFunction {
19    Empty { return_type }.boxed()
20}
21
22#[derive(Debug)]
23struct Empty {
24    return_type: DataType,
25}
26
27#[async_trait::async_trait]
28impl TableFunction for Empty {
29    fn return_type(&self) -> DataType {
30        self.return_type.clone()
31    }
32
33    async fn eval<'a>(&'a self, _input: &'a DataChunk) -> BoxStream<'a, Result<DataChunk>> {
34        futures_util::stream::empty().boxed()
35    }
36}
risingwave_expr/table_function/empty.rs

risingwave_expr/table_function/
empty.rs
