datafusion 0.2.4

// Copyright 2018 Grove Enterprises LLC
//
// 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::io::Error;
use std::rc::Rc;

use arrow::array::Array;
use arrow::datatypes::{DataType, Field};

use super::sqlparser::ParserError;

/// Value holder for all supported data types
#[derive(Debug, Clone, PartialEq)]
pub enum ScalarValue {
    Null,
    Boolean(bool),
    Float32(f32),
    Float64(f64),
    Int8(i8),
    Int16(i16),
    Int32(i32),
    Int64(i64),
    UInt8(u8),
    UInt16(u16),
    UInt32(u32),
    UInt64(u64),
    Utf8(String),
    Struct(Vec<ScalarValue>),
}

#[derive(Clone)]
pub enum Value {
    Column(Rc<Array>),
    Scalar(Rc<ScalarValue>),
}

/// Scalar function. User-defined implementations will be dynamically loaded at runtime.
pub trait ScalarFunction {
    fn name(&self) -> String;
    fn args(&self) -> Vec<Field>;
    fn return_type(&self) -> DataType;
    fn execute(&self, args: Vec<Rc<Value>>) -> Result<Rc<Value>, ExecutionError>;
}

#[derive(Debug)]
pub enum ExecutionError {
    IoError(Error),
    ParserError(ParserError),
    Custom(String),
}

impl From<Error> for ExecutionError {
    fn from(e: Error) -> Self {
        ExecutionError::IoError(e)
    }
}

impl From<String> for ExecutionError {
    fn from(e: String) -> Self {
        ExecutionError::Custom(e)
    }
}

impl From<ParserError> for ExecutionError {
    fn from(e: ParserError) -> Self {
        ExecutionError::ParserError(e)
    }
}