mustafasrepo commented on code in PR #6904: URL: https://github.com/apache/arrow-datafusion/pull/6904#discussion_r1259869497
########## datafusion/physical-expr/src/aggregate/groups_accumulator/mod.rs: ########## @@ -0,0 +1,122 @@ +// 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. + +//! Vectorized [`GroupsAccumulator`] + +pub(crate) mod accumulate; +mod adapter; +pub use adapter::GroupsAccumulatorAdapter; + +pub(crate) mod bool_op; +pub(crate) mod prim_op; + +use arrow_array::{ArrayRef, BooleanArray}; +use datafusion_common::Result; + +/// `GroupAccumulator` implements a single aggregate (e.g. AVG) and +/// stores the state for *all* groups internally. +/// +/// Each group is assigned a `group_index` by the hash table and each +/// accumulator manages the specific state, one per group_index. +/// +/// group_indexes are contiguous (there aren't gaps), and thus it is +/// expected that each GroupAccumulator will use something like `Vec<..>` +/// to store the group states. +pub trait GroupsAccumulator: Send { + /// Updates the accumulator's state from its arguments, encoded as + /// a vector of [`ArrayRef`]s. + /// + /// * `values`: the input arguments to the accumulator + /// + /// * `group_indices`: To which groups do the rows in `values` + /// belong, group id) + /// + /// * `opt_filter`: if present, only update aggregate state using + /// `values[i]` if `opt_filter[i]` is true + /// + /// * `total_num_groups`: the number of groups (the largest + /// group_index is thus `total_num_groups - 1`). + /// + /// Note thats subsequent calls to update_batch may have larger + /// total_num_groups as new groups are seen. + fn update_batch( + &mut self, + values: &[ArrayRef], + group_indices: &[usize], + opt_filter: Option<&BooleanArray>, + total_num_groups: usize, + ) -> Result<()>; + + /// Returns the final aggregate value for each group as a single + /// `RecordBatch`, resetting the internal state. + /// + /// The rows returned *must* be in group_index order: The value + /// for group_index 0, followed by 1, etc. Any group_index that + /// did not have values, should be null. + /// + /// For example, a `SUM` accumulator maintains a running sum for + /// each group, and `evaluate` will produce that running sum as + /// its output for all groups, in group_index order + /// + /// The accumulator should free to release / reset it is internal + /// state after this call to the same as it was after being + /// initially created. + fn evaluate(&mut self) -> Result<ArrayRef>; + + /// Returns the intermediate aggregate state for this accumulator, + /// used for multi-phase grouping, resetting its internal state. + /// + /// The rows returned *must* be in group_index order: The value + /// for group_index 0, followed by 1, etc. Any group_index that + /// did not have values, should be null. + /// + /// For example, `AVG` might return two arrays: `SUM` and `COUNT` + /// but the `MIN` aggregate would just return a single array. + /// + /// Note more sophisticated internal state can be passed as + /// single `StructArray` rather than multiple arrays. + /// + /// The accumulator should free to release / reset it is internal + /// state after this call to the same as it was after being + /// initially created. + fn state(&mut self) -> Result<Vec<ArrayRef>>; + + /// Merges intermediate state (the output from [`Self::state`]) + /// into this accumulator's values. + /// + /// For some aggregates (such as `SUM`), `merge_batch` is the same + /// as `update_batch`, but for some aggregrates (such as `COUNT`, Review Comment: ```suggestion /// as `update_batch`, but for some aggregates (such as `COUNT`, ``` -- 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]
