mbrobbel commented on code in PR #8408: URL: https://github.com/apache/arrow-rs/pull/8408#discussion_r2378240955
########## parquet/src/arrow/schema/extension.rs: ########## @@ -0,0 +1,68 @@ +// 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. + +//! Arrow Extension Type Support for Parquet +//! +//! This module contains mapping code to map Parquet [`LogicalType`]s to/from +//! Arrow [`ExtensionType`]s. +//! +//! Extension types are represented using the metadata from Arrow [`Field`]s +//! with the key "ARROW:extension:name". + +use crate::basic::LogicalType; +use crate::schema::types::Type; +use arrow_schema::extension::ExtensionType; +use arrow_schema::Field; + +/// Adds extension type metadata, if necessary, based on the Parquet field's +/// [`LogicalType`] +/// +/// Some Parquet logical types, such as Variant, do not map directly to an +/// Arrow DataType, and instead are represented by an Arrow ExtensionType. +/// Extension types are attached to Arrow Fields via metadata. +pub(crate) fn add_extension_type(arrow_field: Field, parquet_type: &Type) -> Field { + let result = match parquet_type.get_basic_info().logical_type() { + #[cfg(feature = "variant_experimental")] + Some(LogicalType::Variant) => { + arrow_field.with_extension_type(parquet_variant_compute::VariantType) + } + // TODO add other LogicalTypes here + _ => arrow_field, + }; + result +} + +/// Return the Parquet logical type to use for the specified Arrow field, if any. +#[cfg(feature = "variant_experimental")] +pub(crate) fn logical_type_for_struct(field: &Field) -> Option<LogicalType> { + use parquet_variant_compute::VariantType; + // Check the name (= quick and cheap) and only try_extension_type if the name matches + // to avoid unnecessary String allocations in ArrowError Review Comment: Should we add a method to `Field` for this? ########## parquet/src/arrow/schema/extension.rs: ########## @@ -0,0 +1,62 @@ +// 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. + +//! Arrow Extension Type Support for Parquet +//! +//! This module contains mapping code to map Parquet [`LogicalType`]s to/from +//! Arrow [`ExtensionType`]s. +//! +//! Extension types are represented using the metadata from Arrow [`Field`]s +//! with the key "ARROW:extension:name". + +use crate::basic::LogicalType; +use crate::schema::types::Type; +use arrow_schema::extension::ExtensionType; +use arrow_schema::Field; + +/// Adds extension type metadata, if necessary, based on the Parquet field's +/// [`LogicalType`] +/// +/// Some Parquet logical types, such as Variant, do not map directly to an +/// Arrow DataType, and instead are represented by an Arrow ExtensionType. +/// Extension types are attached to Arrow Fields via metadata. +pub(crate) fn add_extension_type(arrow_field: Field, parquet_type: &Type) -> Field { + let result = match parquet_type.get_basic_info().logical_type() { + #[cfg(feature = "variant_experimental")] + Some(LogicalType::Variant) => { + arrow_field.with_extension_type(parquet_variant_compute::VariantType) + } + // TODO add other LogicalTypes here + _ => arrow_field, + }; + result Review Comment: ```suggestion match parquet_type.get_basic_info().logical_type() { #[cfg(feature = "variant_experimental")] Some(LogicalType::Variant) => { arrow_field.with_extension_type(parquet_variant_compute::VariantType) } // TODO add other LogicalTypes here _ => arrow_field, } ``` ########## parquet/src/variant.rs: ########## @@ -67,37 +65,29 @@ //! # } //! ``` //! -//! # Example: Writing JSON with a Parquet file with Variant column +//! # Example: Writing JSON into a Parquet file with Variant column //! ```rust //! # use std::sync::Arc; //! # use arrow_array::{ArrayRef, RecordBatch, StringArray}; -//! # use parquet::variant::compute::json_to_variant; -//! # use parquet::variant::compute::VariantArray; +//! # use arrow_schema::Schema; +//! # use parquet::variant::{json_to_variant, VariantArray}; //! # use parquet::arrow::ArrowWriter; //! # fn main() -> Result<(), parquet::errors::ParquetError> { //! // Create an array of JSON strings, simulating a column of JSON data -//! // TODO use StringViewArray when available -//! let input_array = StringArray::from(vec![ +//! let input_array: ArrayRef = Arc::new(StringArray::from(vec![ //! Some(r#"{"name": "Alice", "age": 30}"#), //! Some(r#"{"name": "Bob", "age": 25, "address": {"city": "New York"}}"#), //! None, //! Some("{}"), -//! ]); -//! let input_array: ArrayRef = Arc::new(input_array); +//! ])); //! //! // Convert the JSON strings to a VariantArray //! let array: VariantArray = json_to_variant(&input_array)?; -//! -//! // TODO support writing VariantArray directly -//! // at the moment it panics when trying to downcast to a struct array -//! // https://github.com/apache/arrow-rs/issues/8296 -//! // let array: ArrayRef = Arc::new(array); -//! let array: ArrayRef = Arc::new(array.into_inner()); -//! //! // create a RecordBatch with the VariantArray -//! let batch = RecordBatch::try_from_iter(vec![("data", array)])?; +//! let schema = Schema::new(vec![array.field("data")]); +//! let batch = RecordBatch::try_new(Arc::new(schema), vec![ArrayRef::from(array)])?; //! -//! // write the RecordBatch to a Parquet file +//! // write the RecordBatch to a Parquet file as normal //! let file = std::fs::File::create("variant-json.parquet")?; //! let mut writer = ArrowWriter::try_new(file, batch.schema(), None)?; //! writer.write(&batch)?; Review Comment: ```suggestion //! // create a RecordBatch with the VariantArray //! let schema = Schema::new(vec![array.field("data")]); //! let batch = RecordBatch::try_new(Arc::new(schema), vec![ArrayRef::from(array)])?; //! //! // write the RecordBatch to a Parquet file as normal //! let file = std::fs::File::create("variant-json.parquet")?; //! let mut writer = ArrowWriter::try_new(file, batch.schema(), None)?; //! writer.write(&batch)?; ``` -- This is an automated message from the Apache Git Service. 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