xudong963 commented on code in PR #20768: URL: https://github.com/apache/datafusion/pull/20768#discussion_r2917168108
########## datafusion/common/src/utils/aggregate.rs: ########## @@ -0,0 +1,149 @@ +// 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. + +//! Scalar-level aggregation utilities for statistics merging. +//! +//! Provides a cheap pairwise [`ScalarValue`] addition that directly +//! extracts inner primitive values, avoiding the expensive +//! `ScalarValue::add` path (which round-trips through Arrow arrays). +use arrow::datatypes::i256; + +use crate::stats::Precision; +use crate::{Result, ScalarValue}; + +/// Saturating addition for [`i256`] (which lacks a built-in +/// `saturating_add`). Returns `i256::MAX` on positive overflow and +/// `i256::MIN` on negative overflow. +#[inline] +fn i256_saturating_add(a: i256, b: i256) -> i256 { + match a.checked_add(b) { + Some(sum) => sum, + None => { + // If b is non-negative the overflow is positive, otherwise + // negative. + if b >= i256::ZERO { + i256::MAX + } else { + i256::MIN + } + } + } +} + +/// Add two [`ScalarValue`]s by directly extracting and adding their +/// inner primitive values. +/// +/// This avoids `ScalarValue::add` which converts both operands to +/// single-element Arrow arrays, runs the `add_wrapping` kernel, and +/// converts the result back — 3 heap allocations per call. +/// +/// For non-primitive types, falls back to `ScalarValue::add`. +pub(crate) fn scalar_add(lhs: &ScalarValue, rhs: &ScalarValue) -> Result<ScalarValue> { + macro_rules! add_int { + ($lhs:expr, $rhs:expr, $VARIANT:ident) => { + match ($lhs, $rhs) { + (ScalarValue::$VARIANT(Some(a)), ScalarValue::$VARIANT(Some(b))) => { + Ok(ScalarValue::$VARIANT(Some(a.saturating_add(*b)))) + } + (ScalarValue::$VARIANT(None), other) + | (other, ScalarValue::$VARIANT(None)) => Ok(other.clone()), + _ => unreachable!(), + } + }; + } + + macro_rules! add_decimal { + ($lhs:expr, $rhs:expr, $VARIANT:ident) => { + match ($lhs, $rhs) { + ( + ScalarValue::$VARIANT(Some(a), p, s), + ScalarValue::$VARIANT(Some(b), _, _), + ) => Ok(ScalarValue::$VARIANT(Some(a.saturating_add(*b)), *p, *s)), + (ScalarValue::$VARIANT(None, _, _), other) + | (other, ScalarValue::$VARIANT(None, _, _)) => Ok(other.clone()), + _ => unreachable!(), + } + }; + } + + macro_rules! add_float { + ($lhs:expr, $rhs:expr, $VARIANT:ident) => { + match ($lhs, $rhs) { + (ScalarValue::$VARIANT(Some(a)), ScalarValue::$VARIANT(Some(b))) => { + Ok(ScalarValue::$VARIANT(Some(*a + *b))) + } + (ScalarValue::$VARIANT(None), other) + | (other, ScalarValue::$VARIANT(None)) => Ok(other.clone()), + _ => unreachable!(), + } + }; + } + + match lhs { + ScalarValue::Int8(_) => add_int!(lhs, rhs, Int8), + ScalarValue::Int16(_) => add_int!(lhs, rhs, Int16), + ScalarValue::Int32(_) => add_int!(lhs, rhs, Int32), + ScalarValue::Int64(_) => add_int!(lhs, rhs, Int64), + ScalarValue::UInt8(_) => add_int!(lhs, rhs, UInt8), + ScalarValue::UInt16(_) => add_int!(lhs, rhs, UInt16), + ScalarValue::UInt32(_) => add_int!(lhs, rhs, UInt32), + ScalarValue::UInt64(_) => add_int!(lhs, rhs, UInt64), + ScalarValue::Float16(_) => add_float!(lhs, rhs, Float16), + ScalarValue::Float32(_) => add_float!(lhs, rhs, Float32), + ScalarValue::Float64(_) => add_float!(lhs, rhs, Float64), + ScalarValue::Decimal32(_, _, _) => add_decimal!(lhs, rhs, Decimal32), + ScalarValue::Decimal64(_, _, _) => add_decimal!(lhs, rhs, Decimal64), + ScalarValue::Decimal128(_, _, _) => add_decimal!(lhs, rhs, Decimal128), Review Comment: For Decimal128(Some(a), p, s), saturating to i128::MAX doesn't respect the precision constraint. A Decimal128 with precision 5 can't hold i128::MAX. For example: ``` let a = Decimal128(Some(99999), 5, 2); // 999.99 let b = Decimal128(Some(99999), 5, 2); // 999.99 ``` ########## datafusion/common/src/utils/aggregate.rs: ########## @@ -0,0 +1,149 @@ +// Licensed to the Apache Software Foundation (ASF) under one Review Comment: Not sure if we can put it into a higher level, is it possible that other nodes may use this code in the future, not only agg. -- 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]
