sweb commented on a change in pull request #9428: URL: https://github.com/apache/arrow/pull/9428#discussion_r577945055
########## File path: rust/arrow/src/compute/kernels/regexp.rs ########## @@ -0,0 +1,117 @@ +// 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. + +//! Defines kernel to extract substrings based on a regular +//! expression of a \[Large\]StringArray + +use crate::array::{ + Array, ArrayRef, GenericStringArray, GenericStringBuilder, LargeStringArray, + StringArray, StringOffsetSizeTrait, +}; +use crate::datatypes::DataType; +use crate::error::{ArrowError, Result}; + +use std::sync::Arc; + +use regex::Regex; + +fn generic_regexp_extract<OffsetSize: StringOffsetSizeTrait>( + array: &GenericStringArray<OffsetSize>, + re: &Regex, + idx: usize, +) -> Result<ArrayRef> { + let mut builder: GenericStringBuilder<OffsetSize> = GenericStringBuilder::new(0); + + for maybe_value in array.iter() { + match maybe_value { + Some(value) => match re.captures(value) { + Some(caps) => { + let m = caps.get(idx).ok_or_else(|| { + ArrowError::ComputeError(format!( + "Regexp has no group with index {}", + idx + )) + })?; + builder.append_value(m.as_str())? + } + None => builder.append_null()?, + }, + None => builder.append_null()?, + } + } + Ok(Arc::new(builder.finish())) +} + +/// Extracts a specific group matched by a regular expression for a given String array. +/// Group index 0 returns the whole match, index 1 returns the first group and so on. Please +/// refer to regex crate for details on pattern specifics. +pub fn regexp_extract(array: &Array, pattern: &str, idx: usize) -> Result<ArrayRef> { Review comment: Hey @jorgecarleitao thank you very much for your review. I will try to address your comments in the next days. Since @seddonm1 remarked that Postgres compatibility, I was thinking about changing the function signature of the kernel to: ``` pub fn regexp_match(array: &Array, pattern: &str) -> Result<ArrayRef> ``` where the returned array is of type `GenericListArray` with values of type `&str`. A list is closer to the Postgres signature and would provide the flexibility to choose multiple groups. Would this be fine as well or is `Vec<ArrayRef>` preferable to you? ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
