mustafasrepo commented on code in PR #6904: URL: https://github.com/apache/arrow-datafusion/pull/6904#discussion_r1260709846
########## 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 + let new_accumulators = total_num_groups - self.states.len(); + for _ in 0..new_accumulators { + let accumulator = (self.factory)()?; + let state = AccumulatorState::new(accumulator); + self.allocation_bytes += state.size(); + self.states.push(state); + } + + self.allocation_bytes += + std::mem::size_of::<AccumulatorState>() * self.states.capacity(); + self.allocation_bytes -= vec_size_pre; + Ok(()) + } + + /// invokes f(accumulator, values) for each group that has values + /// in group_indices. + /// + /// This function first reorders the input and filter so that + /// values for each group_index are contiguous and then invokes f + /// on the contiguous ranges, to minimize per-row overhead + /// + /// ```text + /// ┌─────────┐ ┌─────────┐ ┌ ─ ─ ─ ─ ┐ ┌─────────┐ ┌ ─ ─ ─ ─ ┐ + /// │ ┌─────┐ │ │ ┌─────┐ │ ┌─────┐ ┏━━━━━┓ │ ┌─────┐ │ ┌─────┐ + /// │ │ 2 │ │ │ │ 200 │ │ │ │ t │ │ ┃ 0 ┃ │ │ 200 │ │ │ │ t │ │ + /// │ ├─────┤ │ │ ├─────┤ │ ├─────┤ ┣━━━━━┫ │ ├─────┤ │ ├─────┤ + /// │ │ 2 │ │ │ │ 100 │ │ │ │ f │ │ ┃ 0 ┃ │ │ 300 │ │ │ │ t │ │ + /// │ ├─────┤ │ │ ├─────┤ │ ├─────┤ ┣━━━━━┫ │ ├─────┤ │ ├─────┤ + /// │ │ 0 │ │ │ │ 200 │ │ │ │ t │ │ ┃ 1 ┃ │ │ 200 │ │ │ │NULL │ │ + /// │ ├─────┤ │ │ ├─────┤ │ ├─────┤ ────────▶ ┣━━━━━┫ │ ├─────┤ │ ├─────┤ + /// │ │ 1 │ │ │ │ 200 │ │ │ │NULL │ │ ┃ 2 ┃ │ │ 200 │ │ │ │ t │ │ + /// │ ├─────┤ │ │ ├─────┤ │ ├─────┤ ┣━━━━━┫ │ ├─────┤ │ ├─────┤ + /// │ │ 0 │ │ │ │ 300 │ │ │ │ t │ │ ┃ 2 ┃ │ │ 100 │ │ │ │ f │ │ + /// │ └─────┘ │ │ └─────┘ │ └─────┘ ┗━━━━━┛ │ └─────┘ │ └─────┘ + /// └─────────┘ └─────────┘ └ ─ ─ ─ ─ ┘ └─────────┘ └ ─ ─ ─ ─ ┘ + /// + /// values opt_filter logical group values opt_filter Review Comment: I think this line and columns above mis-aligned, Is this the case? -- This is an automated message from the Apache Git Service. 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