jorgecarleitao commented on a change in pull request #8090: URL: https://github.com/apache/arrow/pull/8090#discussion_r481274249
########## File path: rust/datafusion/src/execution/physical_plan/string_expressions.rs ########## @@ -0,0 +1,63 @@ +// 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. + +//! String expressions + +use crate::error::{ExecutionError, Result}; +use arrow::array::{Array, ArrayRef, StringArray, StringBuilder}; + +macro_rules! downcast_vec { + ($ARGS:expr, $ARRAY_TYPE:ident) => {{ + $ARGS + .iter() + .map(|e| match e.as_any().downcast_ref::<$ARRAY_TYPE>() { + Some(array) => Ok(array), + _ => Err(ExecutionError::General("failed to downcast".to_string())), + }) + }}; +} + +/// concatenate string columns together. +pub fn concatenate(args: &[ArrayRef]) -> Result<StringArray> { + // downcast all arguments to strings + let args = downcast_vec!(args, StringArray).collect::<Result<Vec<&StringArray>>>()?; + // do not accept 0 arguments. + assert!(args.len() != 0); Review comment: Thanks for the suggestions 👍 I've added an error when the plan has 0 arguments. ---------------------------------------------------------------- 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: [email protected]
