vustef commented on code in PR #8715: URL: https://github.com/apache/arrow-rs/pull/8715#discussion_r2496044182
########## parquet/src/arrow/schema/virtual_type.rs: ########## @@ -0,0 +1,141 @@ +// 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. + +//! RowNumber +//! + +use arrow_schema::{ArrowError, DataType, Field, extension::ExtensionType}; + +/// The extension type for `8-bit Boolean`. +/// +/// Extension name: `arrow.row_number`. +/// +/// The storage type of the extension is `Int64`. +/// +#[derive(Debug, Default, Clone, Copy, PartialEq)] +pub struct RowNumber; + +impl ExtensionType for RowNumber { + const NAME: &'static str = "arrow.virtual.row_number"; // TODO @vustef: What should it be named? + + type Metadata = &'static str; + + fn metadata(&self) -> &Self::Metadata { + &"" + } + + fn serialize_metadata(&self) -> Option<String> { + Some(String::default()) + } + + fn deserialize_metadata(metadata: Option<&str>) -> Result<Self::Metadata, ArrowError> { + if metadata.is_some_and(str::is_empty) { + Ok("") + } else { + Err(ArrowError::InvalidArgumentError( + "RowNumber extension type expects an empty string as metadata".to_owned(), + )) + } + } + + fn supports_data_type(&self, data_type: &DataType) -> Result<(), ArrowError> { + match data_type { + DataType::Int64 => Ok(()), + data_type => Err(ArrowError::InvalidArgumentError(format!( + "RowNumber data type mismatch, expected Int64, found {data_type}" + ))), + } + } + + fn try_new(data_type: &DataType, _metadata: Self::Metadata) -> Result<Self, ArrowError> { + Self.supports_data_type(data_type).map(|_| Self) + } +} + +#[cfg(test)] +mod tests { + use arrow_schema::{ + ArrowError, DataType, Field, + extension::{EXTENSION_TYPE_METADATA_KEY, EXTENSION_TYPE_NAME_KEY}, + }; + + use super::*; + + #[test] + fn valid() -> Result<(), ArrowError> { + let mut field = Field::new("", DataType::Int64, false); + field.try_with_extension_type(RowNumber)?; + field.try_extension_type::<RowNumber>()?; + + Ok(()) + } + + #[test] + #[should_panic(expected = "Field extension type name missing")] + fn missing_name() { + let field = Field::new("", DataType::Int64, false).with_metadata( + [(EXTENSION_TYPE_METADATA_KEY.to_owned(), "".to_owned())] + .into_iter() + .collect(), + ); + field.extension_type::<RowNumber>(); + } + + #[test] + #[should_panic(expected = "expected Int64, found Int32")] + fn invalid_type() { + Field::new("", DataType::Int32, false).with_extension_type(RowNumber); + } + + #[test] + #[should_panic(expected = "RowNumber extension type expects an empty string as metadata")] + fn missing_metadata() { + let field = Field::new("", DataType::Int64, false).with_metadata( + [(EXTENSION_TYPE_NAME_KEY.to_owned(), RowNumber::NAME.to_owned())] + .into_iter() + .collect(), + ); + field.extension_type::<RowNumber>(); + } + + #[test] + #[should_panic(expected = "RowNumber extension type expects an empty string as metadata")] + fn invalid_metadata() { + let field = Field::new("", DataType::Int64, false).with_metadata( + [ + (EXTENSION_TYPE_NAME_KEY.to_owned(), RowNumber::NAME.to_owned()), + ( + EXTENSION_TYPE_METADATA_KEY.to_owned(), + "non-empty".to_owned(), + ), + ] + .into_iter() + .collect(), + ); + field.extension_type::<RowNumber>(); + } +} + +/// Returns `true` if the field is a virtual column. +/// +/// Virtual columns have extension type names starting with `arrow.virtual.`. +pub fn is_virtual_column(field: &Field) -> bool { + // TODO @vustef: Make this more typed through another approach that doesn't rely on a naming convention. Review Comment: I plan to have something smarter here if possible, i.e. something that would have help from type system. -- 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]
