viirya commented on code in PR #4393: URL: https://github.com/apache/arrow-rs/pull/4393#discussion_r1248119742
########## arrow-array/src/scalar.rs: ########## @@ -0,0 +1,116 @@ +// 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::Array; + +/// A possibly [`Scalar`] [`Array`] +/// +/// This allows optimised binary kernels where one or more arguments are constant +/// +/// ``` +/// # use arrow_array::*; +/// # use arrow_buffer::{BooleanBuffer, MutableBuffer, NullBuffer}; +/// # use arrow_schema::ArrowError; +/// # +/// fn eq_impl<T: ArrowPrimitiveType>( +/// a: &PrimitiveArray<T>, +/// a_scalar: bool, +/// b: &PrimitiveArray<T>, +/// b_scalar: bool, +/// ) -> BooleanArray { +/// let (array, scalar) = match (a_scalar, b_scalar) { +/// (true, true) | (false, false) => { +/// let len = a.len().min(b.len()); +/// let nulls = NullBuffer::union(a.nulls(), b.nulls()); +/// let buffer = BooleanBuffer::collect_bool(len, |idx| a.value(idx) == b.value(idx)); +/// return BooleanArray::new(buffer, nulls); +/// } +/// (true, false) => (b, (a.null_count() == 0).then(|| a.value(0))), +/// (false, true) => (a, (b.null_count() == 0).then(|| b.value(0))), +/// }; +/// match scalar { +/// Some(v) => { +/// let len = array.len(); +/// let nulls = array.nulls().cloned(); +/// let buffer = BooleanBuffer::collect_bool(len, |idx| array.value(idx) == v); +/// BooleanArray::new(buffer, nulls) +/// } +/// None => BooleanArray::new_null(array.len()), +/// } +/// } +/// +/// pub fn eq(l: &dyn Datum, r: &dyn Datum) -> Result<BooleanArray, ArrowError> { +/// let (l_array, l_scalar) = l.get(); +/// let (r_array, r_scalar) = r.get(); +/// downcast_primitive_array!( +/// (l_array, r_array) => Ok(eq_impl(l_array, l_scalar, r_array, r_scalar)), +/// (a, b) => Err(ArrowError::NotYetImplemented(format!("{a} == {b}"))), +/// ) +/// } +/// +/// // Comparison of two arrays +/// let a = Int32Array::from(vec![1, 2, 3, 4, 5]); +/// let b = Int32Array::from(vec![1, 2, 4, 7, 3]); +/// let r = eq(&a, &b).unwrap(); +/// let values: Vec<_> = r.values().iter().collect(); +/// assert_eq!(values, &[true, true, false, false, false]); +/// +/// // Comparison of an array and a scalar +/// let a = Int32Array::from(vec![1, 2, 3, 4, 5]); +/// let b = Int32Array::from(vec![1]); +/// let r = eq(&a, &Scalar::new(&b)).unwrap(); +/// let values: Vec<_> = r.values().iter().collect(); +/// assert_eq!(values, &[true, false, false, false, false]); +pub trait Datum { + /// Returns the value for this [`Datum`] and a boolean indicating if the value is scalar + fn get(&self) -> (&dyn Array, bool); +} + +impl<T: Array> Datum for T { + fn get(&self) -> (&dyn Array, bool) { + (self, false) + } +} Review Comment: Yea, that is what I wanted to ask, I think. Not all arrays with length 1 are all scalars, but only wrapped with `Scalar` they are scalars. The view maybe be reversed. Not array is treated as scalar but scalar is treated as array. When any one wants to talk with this crate, this crate only understands language in array. So if you want to mention a scalar, you need to fit it into an array and let this crate know it behaves like a scalar. -- 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]
