jonathanc-n commented on code in PR #17648: URL: https://github.com/apache/datafusion/pull/17648#discussion_r2361251054
########## datafusion/physical-plan/src/repartition/hash.rs: ########## @@ -0,0 +1,137 @@ +// 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. + +//! Hash utilities for repartitioning data + +use arrow::datatypes::DataType; +use datafusion_common::Result; +use datafusion_expr::{ColumnarValue, ScalarUDFImpl}; + +use ahash::RandomState; + +/// Internal hash function used for repartitioning inputs. +/// This is used for partitioned HashJoinExec and partitioned GroupByExec. +/// Currently we use AHash with fixed seeds, but this is subject to change. +/// We make no promises about stability of this function across versions. +/// Currently this is *not* stable across machines since AHash is not stable across platforms, +/// thus this should only be used in a single node context. +#[derive(Debug)] +pub(crate) struct RepartitionHash { + signature: datafusion_expr::Signature, + /// RandomState for consistent hashing - using the same seed as hash joins + random_state: RandomState, +} + +impl PartialEq for RepartitionHash { + fn eq(&self, other: &Self) -> bool { + // RandomState doesn't implement PartialEq, so we just compare signatures + self.signature == other.signature + } +} + +impl Eq for RepartitionHash {} + +impl std::hash::Hash for RepartitionHash { + fn hash<H: std::hash::Hasher>(&self, state: &mut H) { + // Only hash the signature since RandomState doesn't implement Hash + self.signature.hash(state); + } +} + +impl RepartitionHash { + /// Create a new RepartitionHash + pub(crate) fn new() -> Self { + Self { + signature: datafusion_expr::Signature::one_of( + vec![datafusion_expr::TypeSignature::VariadicAny], + datafusion_expr::Volatility::Immutable, + ), + random_state: REPARTITION_RANDOM_STATE, + } + } +} + +impl ScalarUDFImpl for RepartitionHash { + fn as_any(&self) -> &dyn std::any::Any { + self + } + + fn name(&self) -> &str { + "repartition_hash" + } + + fn signature(&self) -> &datafusion_expr::Signature { + &self.signature + } + + fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> { + // Always return UInt64Array regardless of input types + Ok(DataType::UInt64) + } + + fn invoke_with_args( + &self, + args: datafusion_expr::ScalarFunctionArgs, + ) -> Result<ColumnarValue> { + use arrow::array::{Array, UInt64Array}; + use datafusion_common::hash_utils::create_hashes; + use std::sync::Arc; + + if args.args.is_empty() { + return datafusion_common::plan_err!("hash requires at least one argument"); Review Comment: ```suggestion return datafusion_common::plan_err!("repartition_hash requires at least one argument"); ``` ########## datafusion/physical-plan/src/repartition/hash.rs: ########## @@ -0,0 +1,137 @@ +// 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. + +//! Hash utilities for repartitioning data + +use arrow::datatypes::DataType; +use datafusion_common::Result; +use datafusion_expr::{ColumnarValue, ScalarUDFImpl}; + +use ahash::RandomState; + +/// Internal hash function used for repartitioning inputs. +/// This is used for partitioned HashJoinExec and partitioned GroupByExec. +/// Currently we use AHash with fixed seeds, but this is subject to change. +/// We make no promises about stability of this function across versions. +/// Currently this is *not* stable across machines since AHash is not stable across platforms, +/// thus this should only be used in a single node context. +#[derive(Debug)] +pub(crate) struct RepartitionHash { + signature: datafusion_expr::Signature, + /// RandomState for consistent hashing - using the same seed as hash joins + random_state: RandomState, +} + +impl PartialEq for RepartitionHash { + fn eq(&self, other: &Self) -> bool { + // RandomState doesn't implement PartialEq, so we just compare signatures + self.signature == other.signature + } +} + +impl Eq for RepartitionHash {} + +impl std::hash::Hash for RepartitionHash { + fn hash<H: std::hash::Hasher>(&self, state: &mut H) { + // Only hash the signature since RandomState doesn't implement Hash + self.signature.hash(state); + } +} + +impl RepartitionHash { + /// Create a new RepartitionHash + pub(crate) fn new() -> Self { + Self { + signature: datafusion_expr::Signature::one_of( + vec![datafusion_expr::TypeSignature::VariadicAny], + datafusion_expr::Volatility::Immutable, + ), + random_state: REPARTITION_RANDOM_STATE, + } + } +} + +impl ScalarUDFImpl for RepartitionHash { + fn as_any(&self) -> &dyn std::any::Any { + self + } + + fn name(&self) -> &str { + "repartition_hash" + } + + fn signature(&self) -> &datafusion_expr::Signature { + &self.signature + } + + fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> { + // Always return UInt64Array regardless of input types + Ok(DataType::UInt64) + } + + fn invoke_with_args( + &self, + args: datafusion_expr::ScalarFunctionArgs, + ) -> Result<ColumnarValue> { + use arrow::array::{Array, UInt64Array}; + use datafusion_common::hash_utils::create_hashes; + use std::sync::Arc; + + if args.args.is_empty() { + return datafusion_common::plan_err!("hash requires at least one argument"); + } + + // Convert all arguments to arrays + let arrays = ColumnarValue::values_to_arrays(&args.args)?; + + // Check that all arrays have the same length + let array_len = arrays[0].len(); + for (i, array) in arrays.iter().enumerate() { + if array.len() != array_len { + return datafusion_common::plan_err!( + "All input arrays must have the same length. Array 0 has length {}, but array {} has length {}", + array_len, i, array.len() + ); + } + } + + // If no rows, return an empty UInt64Array + if array_len == 0 { + return Ok(ColumnarValue::Array(Arc::new(UInt64Array::from( + Vec::<u64>::new(), + )))); + } + + // Create hash buffer and compute hashes using DataFusion's internal algorithm + let mut hashes_buffer = vec![0u64; array_len]; + create_hashes(&arrays, &self.random_state, &mut hashes_buffer)?; + + // Return the hash values as a UInt64Array + Ok(ColumnarValue::Array(Arc::new(UInt64Array::from( + hashes_buffer, + )))) + } + + fn documentation(&self) -> Option<&datafusion_expr::Documentation> { + None + } +} + +/// RandomState used by RepartitionExec for consistent hash partitioning +/// This must match the seeds used in RepartitionExec to ensure our hash-based +/// filter expressions compute the same partition assignments as the actual partitioning +const REPARTITION_RANDOM_STATE: RandomState = RandomState::with_seeds(0, 0, 0, 0); Review Comment: Is there a reason this is at the bottom of the file, more idiomatic to put at the top. -- This is an automated message from the Apache Git Service. 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