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// 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 super::rel::*; use super::exec::*; #[derive(Debug)] pub enum DataFrameError { TBD, NotImplemented } impl From<ExecutionError> for DataFrameError { fn from(e: ExecutionError) -> Self { //TODO: DataFrameError::TBD } } impl From<Error> for DataFrameError { fn from(e: Error) -> Self { //TODO: DataFrameError::TBD } } /// DataFrame is an abstraction of a distributed query plan pub trait DataFrame { /// Change the number of partitions fn repartition(&self, n: u32) -> Result<Box<DataFrame>,DataFrameError>; /// Projection fn select(&self, expr: Vec<Rex>) -> Result<Box<DataFrame>,DataFrameError>; /// Selection fn filter(&self, expr: Rex) -> Result<Box<DataFrame>,DataFrameError>; /// Write to CSV ... will support other formats in the future fn write(&self, filename: &str) -> Result<(),DataFrameError>; /// Return an expression representing the specified column fn col(&self, column_name: &str) -> Result<Rex,DataFrameError>; }