risingwave_expr/window_function/
kind.rs

// 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 anyhow::Context;
use enum_as_inner::EnumAsInner;
use parse_display::{Display, FromStr};
use risingwave_common::bail;

use crate::aggregate::AggType;
use crate::Result;

/// Kind of window functions.
#[expect(clippy::large_enum_variant)]
#[derive(Debug, Display, FromStr /* for builtin */, Clone, PartialEq, Eq, Hash, EnumAsInner)]
#[display(style = "snake_case")]
pub enum WindowFuncKind {
    // General-purpose window functions.
    RowNumber,
    Rank,
    DenseRank,
    Lag,
    Lead,

    // Aggregate functions that are used with `OVER`.
    #[display("{0}")]
    Aggregate(AggType),
}

impl WindowFuncKind {
    pub fn from_protobuf(
        window_function_type: &risingwave_pb::expr::window_function::PbType,
    ) -> Result<Self> {
        use risingwave_pb::expr::agg_call::PbKind as PbAggKind;
        use risingwave_pb::expr::window_function::{PbGeneralType, PbType};

        let kind = match window_function_type {
            PbType::General(typ) => match PbGeneralType::try_from(*typ) {
                Ok(PbGeneralType::Unspecified) => bail!("Unspecified window function type"),
                Ok(PbGeneralType::RowNumber) => Self::RowNumber,
                Ok(PbGeneralType::Rank) => Self::Rank,
                Ok(PbGeneralType::DenseRank) => Self::DenseRank,
                Ok(PbGeneralType::Lag) => Self::Lag,
                Ok(PbGeneralType::Lead) => Self::Lead,
                Err(_) => bail!("no such window function type"),
            },
            PbType::Aggregate(kind) => Self::Aggregate(AggType::from_protobuf_flatten(
                PbAggKind::try_from(*kind).context("no such aggregate function type")?,
                None,
                None,
            )?),
            PbType::Aggregate2(agg_type) => Self::Aggregate(AggType::from_protobuf(agg_type)?),
        };
        Ok(kind)
    }
}

impl WindowFuncKind {
    pub fn is_numbering(&self) -> bool {
        matches!(self, Self::RowNumber | Self::Rank | Self::DenseRank)
    }
}
risingwave_expr/window_function/kind.rs

risingwave_expr/window_function/
kind.rs
