scovich commented on code in PR #8021: URL: https://github.com/apache/arrow-rs/pull/8021#discussion_r2261159145
########## parquet-variant-compute/src/variant_get/output/primitive.rs: ########## @@ -0,0 +1,166 @@ +// 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::variant_get::output::OutputBuilder; +use crate::VariantArray; +use arrow::error::Result; + +use arrow::array::{ + Array, ArrayRef, ArrowPrimitiveType, AsArray, BinaryViewArray, NullBufferBuilder, + PrimitiveArray, +}; +use arrow::compute::{cast_with_options, CastOptions}; +use arrow::datatypes::Int32Type; +use arrow_schema::{ArrowError, FieldRef}; +use parquet_variant::{Variant, VariantPath}; +use std::marker::PhantomData; +use std::sync::Arc; + +/// Trait for Arrow primitive types that can be used in the output builder +/// +/// This just exists to add a generic way to convert from Variant to the primitive type +pub(super) trait ArrowPrimitiveVariant: ArrowPrimitiveType { + /// Try to extract the primitive value from a Variant, returning None if it + /// cannot be converted + /// + /// TODO: figure out how to handle coercion/casting + fn from_variant(variant: &Variant) -> Option<Self::Native>; +} + +/// Outputs Primitive arrays +pub(super) struct PrimitiveOutputBuilder<'a, T: ArrowPrimitiveVariant> { + /// What path to extract + path: VariantPath<'a>, + /// Returned output type + as_type: FieldRef, + /// Controls the casting behavior (e.g. error vs substituting null on cast error). + cast_options: CastOptions<'a>, + /// Phantom data for the primitive type + _phantom: PhantomData<T>, +} + +impl<'a, T: ArrowPrimitiveVariant> PrimitiveOutputBuilder<'a, T> { + pub(super) fn new( + path: VariantPath<'a>, + as_type: FieldRef, + cast_options: CastOptions<'a>, + ) -> Self { + Self { + path, + as_type, + cast_options, + _phantom: PhantomData, + } + } +} + +impl<'a, T: ArrowPrimitiveVariant> OutputBuilder for PrimitiveOutputBuilder<'a, T> { + fn partially_shredded( + &self, + variant_array: &VariantArray, + _metadata: &BinaryViewArray, + _value_field: &BinaryViewArray, + typed_value: &ArrayRef, + ) -> arrow::error::Result<ArrayRef> { + // build up the output array element by element + let mut nulls = NullBufferBuilder::new(variant_array.len()); + let mut values = Vec::with_capacity(variant_array.len()); + let typed_value = + cast_with_options(typed_value, self.as_type.data_type(), &self.cast_options)?; + // downcast to the primitive array (e.g. Int32Array, Float64Array, etc) + let typed_value = typed_value.as_primitive::<T>(); + + for i in 0..variant_array.len() { + if variant_array.is_null(i) { + nulls.append_null(); + values.push(T::default_value()); // not used, placeholder + continue; + } + + // if the typed value is null, decode the variant and extract the value + if typed_value.is_null(i) { + // todo follow path Review Comment: > > We'd either have to do all the pathing here (recursively), or caller would have to to extract the struct/array once and recurse on its fields. > > Yes, I was imagining that this would do the pathing here on each row -- I am not sure what you mean by extract the struct array (as I don't think we can extract variants as structs in general, as the structures vary row by row) Right, once we get into "true" (unshredded) variant data, we are stuck going row by row. But we can handle the pathing the the (possibly empty) prefix of perfectly shredded columns on a column-wise basis. Identify them when constructing the builders, and then just "snap" them into place when finalizing the builder. No per-row shenanigans needed. If a path isn't perfectly shredded, then the builder needs to take the variant column as input and finish the pathing row by row. -- 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]
