Weijun-H commented on code in PR #11969: URL: https://github.com/apache/datafusion/pull/11969#discussion_r1719951398
########## datafusion/functions-nested/src/map_extract.rs: ########## @@ -0,0 +1,173 @@ +// 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. + +//! [`ScalarUDFImpl`] definitions for map_extract functions. + +use arrow::array::{ArrayRef, Capacities, MutableArrayData}; +use arrow_array::{make_array, ListArray}; + +use arrow::datatypes::DataType; +use arrow_array::{Array, MapArray}; +use arrow_buffer::OffsetBuffer; +use arrow_schema::Field; +use datafusion_common::utils::get_map_entry_field; + +use datafusion_common::{cast::as_map_array, exec_err, Result}; +use datafusion_expr::{ColumnarValue, ScalarUDFImpl, Signature, Volatility}; +use std::any::Any; +use std::sync::Arc; +use std::vec; + +use crate::utils::make_scalar_function; + +// Create static instances of ScalarUDFs for each function +make_udf_expr_and_func!( + MapExtract, + map_extract, + map key, + "Return a list containing the value for a given key or an empty list if the key is not contained in the map.", + map_extract_udf +); + +#[derive(Debug)] +pub(super) struct MapExtract { + signature: Signature, + aliases: Vec<String>, +} + +impl MapExtract { + pub fn new() -> Self { + Self { + signature: Signature::user_defined(Volatility::Immutable), + aliases: vec![String::from("element_at")], + } + } +} + +impl ScalarUDFImpl for MapExtract { + fn as_any(&self) -> &dyn Any { + self + } + fn name(&self) -> &str { + "map_extract" + } + + fn signature(&self) -> &Signature { + &self.signature + } + + fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> { + if arg_types.len() != 2 { + return exec_err!("map_extract expects two arguments"); + } + let map_type = &arg_types[0]; + let map_fields = get_map_entry_field(map_type)?; Review Comment: The value type is not `List`, so we cannot return it directly. -- 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: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
