UBarney commented on code in PR #19411: URL: https://github.com/apache/datafusion/pull/19411#discussion_r2672449674
########## datafusion/physical-plan/src/joins/array_map.rs: ########## @@ -0,0 +1,540 @@ +// 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 arrow_schema::DataType; +use num_traits::AsPrimitive; +use std::mem::size_of; + +use crate::joins::MapOffset; +use crate::joins::chain::traverse_chain; +use arrow::array::{Array, ArrayRef, AsArray, BooleanArray}; +use arrow::buffer::BooleanBuffer; +use arrow::datatypes::ArrowNumericType; +use datafusion_common::{Result, ScalarValue, internal_err}; + +/// A macro to downcast only supported integer types (up to 64-bit) and invoke a generic function. +/// +/// Usage: `downcast_supported_integer!(data_type => (Method, arg1, arg2, ...))` +/// +/// The `Method` must be an associated method of [`ArrayMap`] that is generic over +/// `<T: ArrowNumericType>` and allow `T::Native: AsPrimitive<u64>`. +macro_rules! downcast_supported_integer { + ($DATA_TYPE:expr => ($METHOD:ident $(, $ARGS:expr)*)) => { + match $DATA_TYPE { + arrow::datatypes::DataType::Int8 => ArrayMap::$METHOD::<arrow::datatypes::Int8Type>($($ARGS),*), + arrow::datatypes::DataType::Int16 => ArrayMap::$METHOD::<arrow::datatypes::Int16Type>($($ARGS),*), + arrow::datatypes::DataType::Int32 => ArrayMap::$METHOD::<arrow::datatypes::Int32Type>($($ARGS),*), + arrow::datatypes::DataType::Int64 => ArrayMap::$METHOD::<arrow::datatypes::Int64Type>($($ARGS),*), + arrow::datatypes::DataType::UInt8 => ArrayMap::$METHOD::<arrow::datatypes::UInt8Type>($($ARGS),*), + arrow::datatypes::DataType::UInt16 => ArrayMap::$METHOD::<arrow::datatypes::UInt16Type>($($ARGS),*), + arrow::datatypes::DataType::UInt32 => ArrayMap::$METHOD::<arrow::datatypes::UInt32Type>($($ARGS),*), + arrow::datatypes::DataType::UInt64 => ArrayMap::$METHOD::<arrow::datatypes::UInt64Type>($($ARGS),*), + _ => { + return internal_err!( + "Unsupported type for ArrayMap: {:?}", + $DATA_TYPE + ); + } + } + }; +} + +/// A dense map for single-column integer join keys within a limited range. +/// +/// Maps join keys to build-side indices using direct array indexing: +/// `data[val - min_val_in_build_side] -> val_idx_in_build_side + 1`. +/// +/// NULL values are ignored on both the build side and the probe side. +/// +/// # Handling Negative Numbers with `wrapping_sub` +/// +/// This implementation supports signed integer ranges (e.g., `[-5, 5]`) efficiently by +/// treating them as `u64` (Two's Complement) and relying on the bitwise properties of +/// wrapping arithmetic (`wrapping_sub`). +/// +/// In Two's Complement representation, `a_signed - b_signed` produces the same bit pattern +/// as `a_unsigned.wrapping_sub(b_unsigned)` (modulo 2^N). This allows us to perform +/// range calculations and zero-based index mapping uniformly for both signed and unsigned +/// types without branching. +/// +/// ## Examples +/// +/// Consider an `Int64` range `[-5, 5]`. +/// * `min_val (-5)` casts to `u64`: `...11111011` (`u64::MAX - 4`) +/// * `max_val (5)` casts to `u64`: `...00000101` (`5`) +/// +/// **1. Range Calculation** +/// +/// ```text +/// In modular arithmetic, this is equivalent to: +/// (5 - (2^64 - 5)) mod 2^64 +/// = (5 - 2^64 + 5) mod 2^64 +/// = (10 - 2^64) mod 2^64 +/// = 10 +/// +/// ``` +/// The resulting `range` (10) correctly represents the size of the interval `[-5, 5]`. +/// +/// **2. Index Lookup (in `get_matched_indices`)** +/// +/// For a probe value of `0` (which is stored as `0u64`): +/// ```text +/// In modular arithmetic, this is equivalent to: +/// (0 - (2^64 - 5)) mod 2^64 +/// = (-2^64 + 5) mod 2^64 +/// = 5 +/// ``` +/// This correctly maps `-5` to index `0`, `0` to index `5`, etc. +#[derive(Debug)] +pub struct ArrayMap { + // data[probSideVal-offset] -> valIdxInBuildSide + 1; 0 for absent + data: Vec<u32>, + // min val in buildSide + offset: u64, + // next[buildSideIdx] -> next matching valIdxInBuildSide + 1; 0 for end of chain. + // If next is empty, it means there are no duplicate keys (no conflicts). + // It uses the same chain-based conflict resolution as [`JoinHashMapType`]. + next: Vec<u32>, + num_of_distinct_key: usize, +} + +impl ArrayMap { + pub fn is_supported_type(data_type: &DataType) -> bool { + matches!( + data_type, + DataType::Int8 + | DataType::Int16 + | DataType::Int32 + | DataType::Int64 + | DataType::UInt8 + | DataType::UInt16 + | DataType::UInt32 + | DataType::UInt64 + ) + } + + pub(crate) fn key_to_u64(v: &ScalarValue) -> Option<u64> { + match v { + ScalarValue::Int8(Some(v)) => Some(*v as u64), + ScalarValue::Int16(Some(v)) => Some(*v as u64), + ScalarValue::Int32(Some(v)) => Some(*v as u64), + ScalarValue::Int64(Some(v)) => Some(*v as u64), + ScalarValue::UInt8(Some(v)) => Some(*v as u64), + ScalarValue::UInt16(Some(v)) => Some(*v as u64), + ScalarValue::UInt32(Some(v)) => Some(*v as u64), + ScalarValue::UInt64(Some(v)) => Some(*v), + _ => None, + } + } + + /// Estimates the maximum memory usage for an `ArrayMap` with the given parameters. + /// + pub fn estimate_memory_size(min_val: u64, max_val: u64, num_rows: usize) -> usize { + let range = Self::calculate_range(min_val, max_val); + let size = (range + 1) as usize; Review Comment: I've added a check to prevent potential overflow when calculating size. -- This is an automated message from the Apache Git Service. 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