mustafasrepo commented on code in PR #6932: URL: https://github.com/apache/arrow-datafusion/pull/6932#discussion_r1265187924
########## datafusion/core/src/physical_plan/aggregates/order/full.rs: ########## @@ -0,0 +1,167 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you 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 datafusion_execution::memory_pool::proxy::VecAllocExt; + +use crate::physical_expr::EmitTo; + +/// Tracks grouping state when the data is ordered entirely by its +/// group keys +/// +/// When the group values are sorted, as soon as we see group `n+1` we +/// know we will never see any rows for group `n again and thus they +/// can be emitted. +/// +/// For example, given `SUM(amt) GROUP BY id` if the input is sorted +/// by `id` as soon as a new `id` value is seen all previous values +/// can be emitted. +/// +/// The state is tracked like this: +/// +/// ```text +/// ┌─────┐ ┌──────────────────┐ +/// │┌───┐│ │ ┌──────────────┐ │ ┏━━━━━━━━━━━━━━┓ +/// ││ 0 ││ │ │ 123 │ │ ┌─────┃ 13 ┃ +/// │└───┘│ │ └──────────────┘ │ │ ┗━━━━━━━━━━━━━━┛ +/// │ ... │ │ ... │ │ +/// │┌───┐│ │ ┌──────────────┐ │ │ current +/// ││12 ││ │ │ 234 │ │ │ +/// │├───┤│ │ ├──────────────┤ │ │ +/// ││12 ││ │ │ 234 │ │ │ +/// │├───┤│ │ ├──────────────┤ │ │ +/// ││13 ││ │ │ 456 │◀┼───┘ +/// │└───┘│ │ └──────────────┘ │ +/// └─────┘ └──────────────────┘ +/// +/// group indices group_values current tracks the most +/// (in group value recent group index +/// order) +/// ``` +/// +/// In this diagram, the current group is `13`, and thus groups +/// `0..12` can be emitted. Note that `13` can not yet be emitted as +/// there may be more values in the next batch with the same group_id. +#[derive(Debug)] +pub(crate) struct GroupOrderingFull { + state: State, + /// Hash values for groups in 0..current + hashes: Vec<u64>, +} + +#[derive(Debug)] +enum State { + /// Seen no input yet + Start, + + /// Data is in progress. `current is the current group for which + /// values are being generated. Can emit `current` - 1 + InProgress { current: usize }, + + /// Seen end of input: all groups can be emitted + Complete, +} + +impl GroupOrderingFull { + pub fn new() -> Self { + Self { + state: State::Start, + hashes: vec![], + } + } + + // How many groups be emitted, or None if no data can be emitted + pub fn emit_to(&self) -> Option<EmitTo> { + match &self.state { + State::Start => None, + State::InProgress { current, .. } => { + if *current == 0 { + // Can not emit if still on the first row + None + } else { + // otherwise emit all rows prior to the current group + Some(EmitTo::First(*current)) + } + } + State::Complete { .. } => Some(EmitTo::All), + } + } + + /// remove the first n groups from the internal state, shifting + /// all existing indexes down by `n`. Returns stored hash values + pub fn remove_groups(&mut self, n: usize) -> &[u64] { + match &mut self.state { + State::Start => panic!("invalid state: start"), + State::InProgress { current } => { + // shift down by n + assert!(*current >= n); + *current -= n; + self.hashes.drain(0..n); + } + State::Complete { .. } => panic!("invalid state: complete"), + }; + &self.hashes + } + + /// Note that the input is complete so any outstanding groups are done as well + pub fn input_done(&mut self) { + self.state = match self.state { + State::Start => State::Complete, + State::InProgress { .. } => State::Complete, + State::Complete => State::Complete, + }; Review Comment: Maybe we can use `self.state = State::Complete;` directly. However, being explicit may be better. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
