mustafasrepo commented on code in PR #6904: URL: https://github.com/apache/arrow-datafusion/pull/6904#discussion_r1260703683
########## datafusion/physical-expr/src/aggregate/groups_accumulator/adapter.rs: ########## @@ -0,0 +1,355 @@ +// 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. + +//! Adapter that makes [`GroupsAccumulator`] out of [`Accumulator`] + +use super::GroupsAccumulator; +use arrow::{ + array::{AsArray, UInt32Builder}, + compute, + datatypes::UInt32Type, +}; +use arrow_array::{ArrayRef, BooleanArray, PrimitiveArray}; +use datafusion_common::{ + utils::get_arrayref_at_indices, DataFusionError, Result, ScalarValue, +}; +use datafusion_expr::Accumulator; + +/// An adpater that implements [`GroupsAccumulator`] for any [`Accumulator`] +/// +/// While [`Accumulator`] are simpler to implement and can support +/// more general calculations (like retractable window functions), +/// they are not as fast as a specialized `GroupsAccumulator`. This +/// interface bridges the gap so the group by operator only operates +/// in terms of [`Accumulator`]. +pub struct GroupsAccumulatorAdapter { + factory: Box<dyn Fn() -> Result<Box<dyn Accumulator>> + Send>, + + /// state for each group, stored in group_index order + states: Vec<AccumulatorState>, + + /// Current memory usage, in bytes. + /// + /// Note this is incrementally updated to avoid size() being a + /// bottleneck, which we saw in earlier implementations. + allocation_bytes: usize, +} + +struct AccumulatorState { + /// [`Accumulator`] that stores the per-group state + accumulator: Box<dyn Accumulator>, + + // scratch space: indexes in the input array that will be fed to + // this accumulator. Stores indexes as `u32` to match the arrow + // `take` kernel input. + indices: Vec<u32>, +} + +impl AccumulatorState { + fn new(accumulator: Box<dyn Accumulator>) -> Self { + Self { + accumulator, + indices: vec![], + } + } + + /// Returns the amount of memory taken by this structre and its accumulator + fn size(&self) -> usize { + self.accumulator.size() + + std::mem::size_of_val(self) + + std::mem::size_of::<u32>() * self.indices.capacity() + } +} + +impl GroupsAccumulatorAdapter { + /// Create a new adapter that will create a new [`Accumulator`] + /// for each group, using the specified factory function + pub fn new<F>(factory: F) -> Self + where + F: Fn() -> Result<Box<dyn Accumulator>> + Send + 'static, + { + let mut new_self = Self { + factory: Box::new(factory), + states: vec![], + allocation_bytes: 0, + }; + new_self.reset_allocation(); + new_self + } + + // Reset the allocation bytes to empty state + fn reset_allocation(&mut self) { + assert!(self.states.is_empty()); + self.allocation_bytes = std::mem::size_of::<GroupsAccumulatorAdapter>(); + } + + /// Ensure that self.accumulators has total_num_groups + fn make_accumulators_if_needed(&mut self, total_num_groups: usize) -> Result<()> { + // can't shrink + assert!(total_num_groups >= self.states.len()); + let vec_size_pre = + std::mem::size_of::<AccumulatorState>() * self.states.capacity(); + + // instanatiate new accumulators Review Comment: ```suggestion // instantiate new accumulators ``` -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
