Samyak2 commented on code in PR #7919: URL: https://github.com/apache/arrow-rs/pull/7919#discussion_r2208020690
########## parquet-variant-compute/src/variant_get.rs: ########## @@ -0,0 +1,202 @@ +// 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 std::sync::Arc; + +use arrow::{ + array::{Array, ArrayRef}, + compute::CastOptions, + error::Result, +}; +use arrow_schema::{ArrowError, Field}; +use parquet_variant::path::VariantPath; + +use crate::{VariantArray, VariantArrayBuilder}; + +/// Returns an array with the specified path extracted from the variant values. +/// +/// The return array type depends on the `as_type` field of the options parameter +/// 1. `as_type: None`: a VariantArray is returned. The values in this new VariantArray will point +/// to the specified path. +/// 2. `as_type: Some(<specific field>)`: an array of the specified type is returned. +pub fn variant_get(input: &ArrayRef, options: GetOptions) -> Result<ArrayRef> { + let variant_array: &VariantArray = input.as_any().downcast_ref().ok_or_else(|| { + ArrowError::InvalidArgumentError( + "expected a VariantArray as the input for variant_get".to_owned(), + ) + })?; + + if let Some(as_type) = options.as_type { + return Err(ArrowError::NotYetImplemented(format!( + "getting a {} from a VariantArray is not implemented yet", + as_type + ))); + } + + let mut builder = VariantArrayBuilder::new(variant_array.len()); + for i in 0..variant_array.len() { + let new_variant = variant_array.value(i); + // TODO: perf? + let new_variant = new_variant.get_path(&options.path); + if let Some(new_variant) = new_variant { + // TODO: we're decoding the value and doing a copy into a variant value again. This + // copy can be much smarter. + builder.append_variant(new_variant); + } else { + builder.append_null(); + } + } + + Ok(Arc::new(builder.build())) +} + +/// Controls the action of the variant_get kernel. +#[derive(Debug, Clone)] +pub struct GetOptions<'a> { + /// What path to extract + pub path: VariantPath<'a>, + /// if `as_type` is None, the returned array will itself be a VariantArray. + /// + /// if `as_type` is `Some(type)` the field is returned as the specified type if possible. To specify returning + /// a Variant, pass a Field with variant type in the metadata. + pub as_type: Option<Field>, Review Comment: > But meanwhile -- I tend to agree with @alamb that we should separate out casting from pathing. If get_path anyway has to return a Variant, somebody (ie arrow array builder) who actually cares about the type will still have to match on the result even if they just panic in the "impossible" case of an unexpected enum variant. Seems better to let the caller do the casting themselves since they probably have a strongly-typed place to put the result. This makes sense. But I'm not sure what you're suggesting here? Should we have a version of `variant_get` here that doesn't do casting and always returns a `VariantArray`? > As a bonus, that would also mean we don't need to define GetOptions at this low level -- get_path only needs to know about VariantPath. Arrow variant compute and the array builders could worry about the rest of the options space. `Variant::get_path` already only knows about `VariantPath`. `GetOptions` is defined in this `parquet-variant-compute` crate. Or are you suggesting that we add a `get_path` method to `VariantArray`? -- 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: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
