alamb commented on code in PR #8044: URL: https://github.com/apache/arrow-rs/pull/8044#discussion_r2256758139
########## parquet-variant-compute/src/cast_to_variant.rs: ########## @@ -0,0 +1,348 @@ +// 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::{VariantArray, VariantArrayBuilder}; +use arrow::array::{Array, AsArray}; +use arrow::datatypes::{ + Float32Type, Float64Type, Int16Type, Int32Type, Int64Type, Int8Type, UInt16Type, UInt32Type, + UInt64Type, UInt8Type, +}; +use arrow_schema::{ArrowError, DataType}; +use parquet_variant::Variant; + +/// Convert the input array of a specific primitive type to a `VariantArray` +/// row by row +macro_rules! primtive_conversion { + ($t:ty, $input:expr, $builder:expr) => {{ + let array = $input.as_primitive::<$t>(); + for i in 0..array.len() { + if array.is_null(i) { + $builder.append_null(); + continue; + } + $builder.append_variant(Variant::from(array.value(i))); + } + }}; +} + +/// Casts a typed arrow [`Array`] to a [`VariantArray`]. This is useful when you +/// need to convert a specific data type +/// +/// # Arguments +/// * `input` - A reference to the input [`ArrayRef`] to cast +/// +/// # Notes +/// If the input array element is null, the corresponding element in the +/// output `VariantArray` will also be null (not `Variant::Null`). +/// +/// # Example +/// ``` +/// # use arrow::array::{Array, ArrayRef, Int64Array}; +/// # use parquet_variant::Variant; +/// # use parquet_variant_compute::cast_to_variant::cast_to_variant; +/// // input is an Int64Array, which will be cast to a VariantArray +/// let input = Int64Array::from(vec![Some(1), None, Some(3)]); +/// let result = cast_to_variant(&input).unwrap(); +/// assert_eq!(result.len(), 3); +/// assert_eq!(result.value(0), Variant::Int64(1)); +/// assert!(result.is_null(1)); // note null, not Variant::Null +/// assert_eq!(result.value(2), Variant::Int64(3)); +/// ``` +pub fn cast_to_variant(input: &dyn Array) -> Result<VariantArray, ArrowError> { + let mut builder = VariantArrayBuilder::new(input.len()); + + let input_type = input.data_type(); + // todo: use `downcast_primitive` to avoid the boilerplate and match more types + match input_type { + DataType::Int8 => { + primtive_conversion!(Int8Type, input, builder); + } + DataType::Int16 => { + primtive_conversion!(Int16Type, input, builder); + } + DataType::Int32 => { + primtive_conversion!(Int32Type, input, builder); + } + DataType::Int64 => { + primtive_conversion!(Int64Type, input, builder); + } + DataType::UInt8 => { + primtive_conversion!(UInt8Type, input, builder); + } + DataType::UInt16 => { + primtive_conversion!(UInt16Type, input, builder); + } + DataType::UInt32 => { + primtive_conversion!(UInt32Type, input, builder); + } + DataType::UInt64 => { + primtive_conversion!(UInt64Type, input, builder); + } + DataType::Float32 => { + primtive_conversion!(Float32Type, input, builder); + } + DataType::Float64 => { + primtive_conversion!(Float64Type, input, builder); + } + dt => { + return Err(ArrowError::CastError(format!( + "Unsupported data type for casting to Variant: {dt:?}", + ))); + } + }; + Ok(builder.build()) +} + +// TODO add cast_with_options that allow specifying Review Comment: I thought more about this, and since there is (currently) no way for a conversion from Variant --> Array to fail, that means the cast options are less obviously relevant (and thus I can't file a ticket as I don't know what it should do) I updated the comment to reflect this ########## parquet-variant-compute/src/cast_to_variant.rs: ########## @@ -0,0 +1,348 @@ +// 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::{VariantArray, VariantArrayBuilder}; +use arrow::array::{Array, AsArray}; +use arrow::datatypes::{ + Float32Type, Float64Type, Int16Type, Int32Type, Int64Type, Int8Type, UInt16Type, UInt32Type, + UInt64Type, UInt8Type, +}; +use arrow_schema::{ArrowError, DataType}; +use parquet_variant::Variant; + +/// Convert the input array of a specific primitive type to a `VariantArray` +/// row by row +macro_rules! primtive_conversion { + ($t:ty, $input:expr, $builder:expr) => {{ + let array = $input.as_primitive::<$t>(); + for i in 0..array.len() { + if array.is_null(i) { + $builder.append_null(); + continue; + } + $builder.append_variant(Variant::from(array.value(i))); + } + }}; +} + +/// Casts a typed arrow [`Array`] to a [`VariantArray`]. This is useful when you +/// need to convert a specific data type +/// +/// # Arguments +/// * `input` - A reference to the input [`ArrayRef`] to cast +/// +/// # Notes +/// If the input array element is null, the corresponding element in the +/// output `VariantArray` will also be null (not `Variant::Null`). +/// +/// # Example +/// ``` +/// # use arrow::array::{Array, ArrayRef, Int64Array}; +/// # use parquet_variant::Variant; +/// # use parquet_variant_compute::cast_to_variant::cast_to_variant; +/// // input is an Int64Array, which will be cast to a VariantArray +/// let input = Int64Array::from(vec![Some(1), None, Some(3)]); +/// let result = cast_to_variant(&input).unwrap(); +/// assert_eq!(result.len(), 3); +/// assert_eq!(result.value(0), Variant::Int64(1)); +/// assert!(result.is_null(1)); // note null, not Variant::Null +/// assert_eq!(result.value(2), Variant::Int64(3)); +/// ``` +pub fn cast_to_variant(input: &dyn Array) -> Result<VariantArray, ArrowError> { + let mut builder = VariantArrayBuilder::new(input.len()); + + let input_type = input.data_type(); + // todo: use `downcast_primitive` to avoid the boilerplate and match more types + match input_type { + DataType::Int8 => { + primtive_conversion!(Int8Type, input, builder); + } + DataType::Int16 => { + primtive_conversion!(Int16Type, input, builder); + } + DataType::Int32 => { + primtive_conversion!(Int32Type, input, builder); + } + DataType::Int64 => { + primtive_conversion!(Int64Type, input, builder); + } + DataType::UInt8 => { + primtive_conversion!(UInt8Type, input, builder); + } + DataType::UInt16 => { + primtive_conversion!(UInt16Type, input, builder); + } + DataType::UInt32 => { + primtive_conversion!(UInt32Type, input, builder); + } + DataType::UInt64 => { + primtive_conversion!(UInt64Type, input, builder); + } + DataType::Float32 => { + primtive_conversion!(Float32Type, input, builder); + } + DataType::Float64 => { + primtive_conversion!(Float64Type, input, builder); + } Review Comment: Indeed it does. However, when I make this change, I get the following errorrs (because we need to implement conversion to/from the other types (like Decimal128 --> i128) <img width="898" height="171" alt="Screenshot 2025-08-06 at 6 42 20 AM" src="https://github.com/user-attachments/assets/5075653c-a2cd-4a69-a1f7-65b14a44ca7e"; /> I think we may have to handle those cases specially. I will file a follow on ticket to do so. ``` error[E0277]: the trait bound `parquet_variant::Variant<'_, '_>: std::convert::From<half::binary16::f16>` is not satisfied --> parquet-variant-compute/src/cast_to_variant.rs:72:52 | 72 | Some(value) => builder.append_variant(Variant::from(value)), | ^^^^^^^ the trait `std::convert::From<half::binary16::f16>` is not implemented for `parquet_variant::Variant<'_, '_>` | = help: the following other types implement trait `std::convert::From<T>`: `parquet_variant::Variant<'_, '_>` implements `std::convert::From<&[u8]>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<&str>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<()>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<bool>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<chrono::datetime::DateTime<chrono::offset::utc::Utc>>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<chrono::naive::date::NaiveDate>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<chrono::naive::datetime::NaiveDateTime>` `parquet_variant::Variant<'_, '_>` implements `std::convert::From<f32>` and 12 others ``` -- This is an automated message from the Apache Git Service. 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