dharanad commented on code in PR #1199: URL: https://github.com/apache/datafusion-comet/pull/1199#discussion_r1901024382
########## native/spark-expr/src/rand.rs: ########## @@ -0,0 +1,261 @@ +// 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::spark_hash::spark_compatible_murmur3_hash; +use arrow_array::builder::Float64Builder; +use arrow_array::{Float64Array, RecordBatch}; +use arrow_schema::{DataType, Schema}; +use datafusion::logical_expr::ColumnarValue; +use datafusion::physical_expr::PhysicalExpr; +use datafusion::physical_expr_common::physical_expr::down_cast_any_ref; +use datafusion_common::ScalarValue; +use datafusion_common::{DataFusionError, Result}; +use std::any::Any; +use std::fmt::Display; +use std::hash::{Hash, Hasher}; +use std::sync::{Arc, Mutex}; + +const DOUBLE_UNIT: f64 = 1.1102230246251565e-16; +const SPARK_MURMUR_ARRAY_SEED: u32 = 0x3c074a61; + +#[derive(Debug, Clone)] +struct XorShiftRandom { + seed: i64, +} + +impl XorShiftRandom { + fn from_init_seed(init_seed: i64) -> Self { + XorShiftRandom { + seed: Self::init_seed(init_seed), + } + } + + fn from_stored_seed(stored_seed: i64) -> Self { + XorShiftRandom { seed: stored_seed } + } + + fn next(&mut self, bits: u8) -> i32 { + let mut next_seed = self.seed ^ (self.seed << 21); + next_seed ^= ((next_seed as u64) >> 35) as i64; + next_seed ^= next_seed << 4; + self.seed = next_seed; + (next_seed & ((1i64 << bits) - 1)) as i32 + } + + pub fn next_f64(&mut self) -> f64 { + let a = self.next(26) as i64; + let b = self.next(27) as i64; + ((a << 27) + b) as f64 * DOUBLE_UNIT + } + + fn init_seed(init: i64) -> i64 { + let bytes_repr = init.to_be_bytes(); + let low_bits = spark_compatible_murmur3_hash(bytes_repr, SPARK_MURMUR_ARRAY_SEED); + let high_bits = spark_compatible_murmur3_hash(bytes_repr, low_bits); + ((high_bits as i64) << 32) | (low_bits as i64 & 0xFFFFFFFFi64) + } +} + +#[derive(Debug)] +pub struct RandExpr { + seed: Arc<dyn PhysicalExpr>, + init_seed_shift: i32, + state_holder: Arc<Mutex<Option<i64>>>, +} + +impl RandExpr { + pub fn new(seed: Arc<dyn PhysicalExpr>, init_seed_shift: i32) -> Self { + Self { + seed, + init_seed_shift, + state_holder: Arc::new(Mutex::new(None::<i64>)), + } + } + + fn extract_init_state(seed: ScalarValue) -> Result<i64> { + if let ScalarValue::Int64(seed_opt) = seed.cast_to(&DataType::Int64)? { + Ok(seed_opt.unwrap_or(0)) + } else { + Err(DataFusionError::Internal( + "unexpected execution branch".to_string(), + )) + } + } + fn evaluate_batch(&self, seed: ScalarValue, num_rows: usize) -> Result<ColumnarValue> { + let mut seed_state = self.state_holder.lock().unwrap(); + let mut rnd = if seed_state.is_none() { + let init_seed = RandExpr::extract_init_state(seed)?; + let init_seed = init_seed.wrapping_add(self.init_seed_shift as i64); + *seed_state = Some(init_seed); + XorShiftRandom::from_init_seed(init_seed) + } else { + let stored_seed = seed_state.unwrap(); + XorShiftRandom::from_stored_seed(stored_seed) + }; + + let mut arr_builder = Float64Builder::with_capacity(num_rows); + std::iter::repeat_with(|| rnd.next_f64()) + .take(num_rows) + .for_each(|v| arr_builder.append_value(v)); + let array_ref = Arc::new(Float64Array::from(arr_builder.finish())); + *seed_state = Some(rnd.seed); + Ok(ColumnarValue::Array(array_ref)) + } +} + +impl Display for RandExpr { + fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { + write!(f, "RAND({})", self.seed) + } +} + +impl PartialEq<dyn Any> for RandExpr { + fn eq(&self, other: &dyn Any) -> bool { + down_cast_any_ref(other) + .downcast_ref::<Self>() + .map(|x| self.seed.eq(&x.seed)) + .unwrap_or(false) + } +} + +impl PhysicalExpr for RandExpr { + fn as_any(&self) -> &dyn Any { + self + } + + fn data_type(&self, _input_schema: &Schema) -> Result<DataType> { + Ok(DataType::Float64) + } + + fn nullable(&self, _input_schema: &Schema) -> Result<bool> { + Ok(false) + } + + fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue> { + match self.seed.evaluate(batch)? { + ColumnarValue::Scalar(seed) => self.evaluate_batch(seed, batch.num_rows()), + ColumnarValue::Array(_arr) => Err(DataFusionError::NotImplemented(format!( + "Only literal seeds are not supported for {}", Review Comment: Error message seems to have a typo -- This is an automated message from the Apache Git Service. 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