rluvaton commented on code in PR #15591: URL: https://github.com/apache/datafusion/pull/15591#discussion_r3796078674
########## datafusion/functions-aggregate-common/src/aggregate/groups_accumulator/block_store/blocked.rs: ########## @@ -0,0 +1,436 @@ +// 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. + +//! Blocked [`BlockStore`] implementation. + +use std::{ + fmt::Debug, + mem, + ops::{Index, IndexMut}, +}; + +use crate::aggregate::groups_accumulator::block_store::{Block, BlockStore}; + +/// Structure used to store aggregation intermediate results in `blocked approach` +/// +/// Aggregation intermediate results will be stored as multiple [`Block`]s +/// (simply you can think a [`Block`] as a `Vec`). And `Blocks` is the structure +/// to represent such multiple [`Block`]s. +/// +/// Blocks are popped in FIFO order by keeping a cursor into `inner`. Popping a +/// block swaps it out in O(1) using `mem::take` and advances the cursor, +/// avoiding the O(n) shift cost of `Vec::remove(0)`. +/// +/// More details about `blocked approach` can see in: [`GroupsAccumulator::supports_blocked_groups`]. +/// +/// [`GroupsAccumulator::supports_blocked_groups`]: datafusion_expr_common::groups_accumulator::GroupsAccumulator::supports_blocked_groups +/// +#[derive(Debug)] +pub struct BlockedBlockStore<B: Block> { Review Comment: I've tried to copy the code `ArrowBytesMap` to `BlockedArrowBytesMap` where the `Block` is: ```rust #[derive(Debug)] struct BufferAndOffsetBlock<O: OffsetSizeTrait> { /// In progress arrow `Buffer` containing all values buffer: BufferBuilder<u8>, /// Offsets into `buffer` for each distinct value. These offsets as used /// directly to create the final `GenericBinaryArray`. The `i`th string is /// stored in the range `offsets[i]..offsets[i+1]` in `buffer`. Null values /// are stored as a zero length string. offsets: Vec<O>, } impl<O: OffsetSizeTrait> Default for BufferAndOffsetBlock<O> { fn default() -> Self { Self::new(INITIAL_BUFFER_CAPACITY) } } impl<O: OffsetSizeTrait> Block for BufferAndOffsetBlock<O> { type T = Vec<u8>; fn new(capacity: usize) -> Self { Self { buffer: BufferBuilder::new(capacity), offsets: vec![O::default()], // first offset is always 0 } } fn fill_default_value(&mut self, fill_len: usize, default_value: Self::T) { for _ in 0..fill_len { self.buffer.append_slice(&default_value); } let mut last_offset = *self.offsets.last().unwrap(); let len_in_bytes = O::usize_as(default_value.len()); for _ in 0..fill_len { self.offsets.push(last_offset + len_in_bytes); last_offset = last_offset + len_in_bytes; } } fn len(&self) -> usize { self.offsets.len() - 1 } } ``` but then I realized the `fill_default_value` will not serve any benefit when called from resize since I will have to update the offsets (zero cost, O(1)) and add to the buffer - expensive since it requires shifting the bytes (unless the default value is 0) -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
