Dandandan commented on code in PR #16136: URL: https://github.com/apache/datafusion/pull/16136#discussion_r2104357071
########## datafusion/physical-plan/src/aggregates/group_values/single_group_by/primitive/large_primitive.rs: ########## @@ -0,0 +1,139 @@ +// 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 crate::aggregates::group_values::single_group_by::primitive::{ + emit_internal, HashValue, +}; +use crate::aggregates::group_values::GroupValues; +use ahash::RandomState; +use arrow::array::{ + cast::AsArray, ArrayRef, ArrowNativeTypeOp, ArrowPrimitiveType, PrimitiveArray, +}; +use arrow::datatypes::DataType; +use arrow::record_batch::RecordBatch; +use datafusion_common::Result; +use datafusion_execution::memory_pool::proxy::VecAllocExt; +use datafusion_expr::EmitTo; +use hashbrown::hash_table::HashTable; +use std::mem::size_of; + +/// A [`GroupValues`] storing a single column of large primitive values (bits > 64) +/// +/// This specialization is significantly faster than using the more general +/// purpose `Row`s format +pub struct GroupValuesLargePrimitive<T: ArrowPrimitiveType> { + /// The data type of the output array + data_type: DataType, + /// Stores the `(group_index, hash)` based on the hash of its value + /// + /// We also store `hash` is for reducing cost of rehashing. Such cost + /// is obvious in high cardinality group by situation. + /// More details can see: + /// <https://github.com/apache/datafusion/issues/15961> + /// + map: HashTable<(usize, u64)>, + /// The group index of the null value if any + null_group: Option<usize>, + /// The values for each group index + values: Vec<T::Native>, + /// The random state used to generate hashes + random_state: RandomState, +} + +impl<T: ArrowPrimitiveType> GroupValuesLargePrimitive<T> { + pub fn new(data_type: DataType) -> Self { + assert!(PrimitiveArray::<T>::is_compatible(&data_type)); + Self { + data_type, + map: HashTable::with_capacity(128), + values: Vec::with_capacity(128), + null_group: None, + random_state: Default::default(), + } + } +} + +impl<T: ArrowPrimitiveType> GroupValues for GroupValuesLargePrimitive<T> +where + T::Native: HashValue, +{ + fn intern(&mut self, cols: &[ArrayRef], groups: &mut Vec<usize>) -> Result<()> { + assert_eq!(cols.len(), 1); + groups.clear(); + + for v in cols[0].as_primitive::<T>() { + let group_id = match v { + None => *self.null_group.get_or_insert_with(|| { + let group_id = self.values.len(); + self.values.push(Default::default()); + group_id + }), + Some(key) => { + let state = &self.random_state; + let hash = key.hash(state); + let insert = self.map.entry( + hash, + |&(g, _)| unsafe { self.values.get_unchecked(g).is_eq(key) }, + |&(_, h)| h, + ); + + match insert { + hashbrown::hash_table::Entry::Occupied(o) => o.get().0, + hashbrown::hash_table::Entry::Vacant(v) => { + let g = self.values.len(); + v.insert((g, hash)); + self.values.push(key); + g + } + } + } + }; + groups.push(group_id) Review Comment: It can `extend` to groups here by writing this as iterator. -- 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...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
