amladik commented on code in PR #14470: URL: https://github.com/apache/datafusion/pull/14470#discussion_r1945270542
########## datafusion/functions-nested/src/max.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 array_max function. +use crate::sort::array_sort_inner; +use crate::utils::make_scalar_function; +use arrow_array::{Array, ArrayRef, StringArray}; +use arrow_schema::DataType; +use arrow_schema::DataType::{FixedSizeList, LargeList, List}; +use datafusion_common::cast::as_list_array; +use datafusion_common::exec_err; +use datafusion_doc::Documentation; +use datafusion_expr::{ColumnarValue, Expr, ScalarUDFImpl, Signature, Volatility}; +use datafusion_macros::user_doc; +use std::any::Any; +use std::sync::Arc; + +make_udf_expr_and_func!( + ArrayMax, + array_max, + array, + "returns the maximum value in the array.", + array_max_udf +); + +#[user_doc( + doc_section(label = "Array Functions"), + description = "Returns the maximum value in the array.", + syntax_example = "array_max(array)", + sql_example = r#"```sql +> select array_max([3,1,4,2]); ++-----------------------------------------+ +| array_max(List([3,1,4,2])) | ++-----------------------------------------+ +| 4 | ++-----------------------------------------+ +```"#, + argument( + name = "array", + description = "Array expression. Can be a constant, column, or function, and any combination of array operators." + ) +)] +#[derive(Debug)] +pub struct ArrayMax { + signature: Signature, + aliases: Vec<String>, +} + +impl Default for ArrayMax { + fn default() -> Self { + Self::new() + } +} + +impl ArrayMax { + pub fn new() -> Self { + Self { + signature: Signature::array(Volatility::Immutable), + aliases: vec!["list_max".to_string()], + } + } +} + +impl ScalarUDFImpl for ArrayMax { + fn as_any(&self) -> &dyn Any { + self + } + + fn name(&self) -> &str { + "array_max" + } + + fn display_name(&self, args: &[Expr]) -> datafusion_common::Result<String> { + let args_name = args.iter().map(ToString::to_string).collect::<Vec<_>>(); + if args_name.len() != 1 { + return exec_err!("expects 1 arg, got {}", args_name.len()); + } + + Ok(format!("{}", args_name[0])) + } + + fn schema_name(&self, args: &[Expr]) -> datafusion_common::Result<String> { + let args_name = args + .iter() + .map(|e| e.schema_name().to_string()) + .collect::<Vec<_>>(); + if args_name.len() != 1 { + return exec_err!("expects 1 arg, got {}", args_name.len()); + } + + Ok(format!("{}", args_name[0])) + } + + fn signature(&self) -> &Signature { + &self.signature + } + + fn return_type(&self, arg_types: &[DataType]) -> datafusion_common::Result<DataType> { + match &arg_types[0] { + List(field) | LargeList(field) | FixedSizeList(field, _) => { + Ok(field.data_type().clone()) + } + _ => exec_err!( + "Not reachable, data_type should be List, LargeList or FixedSizeList" + ), + } + } + + fn invoke_batch( + &self, + args: &[ColumnarValue], + _number_rows: usize, + ) -> datafusion_common::Result<ColumnarValue> { + make_scalar_function(array_max_inner)(args) + } + + fn aliases(&self) -> &[String] { + &self.aliases + } + + fn documentation(&self) -> Option<&Documentation> { + self.doc() + } +} + +/// array_max SQL function +/// +/// There is one argument for array_max as the array. +/// `array_max(array)` +/// +/// For example: +/// > array_max(\[1, 3, 2]) -> 3 +pub fn array_max_inner(args: &[ArrayRef]) -> datafusion_common::Result<ArrayRef> { + if args.len() != 1 { + return exec_err!("array_max needs one argument"); + } + + match &args[0].data_type() { + List(_) | LargeList(_) | FixedSizeList(_, _) => { + let new_args = vec![ + args[0].clone(), + Arc::new(StringArray::from_iter(vec![Some("DESC")])), + Arc::new(StringArray::from_iter(vec![Some("NULLS LAST")])), + ]; + array_max_internal(&new_args) + } + _ => exec_err!("array_max does not support type: {:?}", args[0].data_type()), + } +} + +fn array_max_internal(args: &[ArrayRef]) -> datafusion_common::Result<ArrayRef> { + let sorted_array = array_sort_inner(args)?; + let result_array = as_list_array(&sorted_array)?.value(0); Review Comment: hey hey i believe code like this would help? At least for all primitive types - for things like Decimal128s and Strings I don't think you can use the PrimitiveArray type let list_array = arr.as_any().downcast_ref::<ListArray>().unwrap(); fn max_list_array_primitives <T>(list_array: &ListArray) -> Result<ColumnarValue> where T: ArrowPrimitiveType, T::Native: Ord, { let mut result = Vec::with_capacity(list_array.len()); for i in 0..list_array.len() { if list_array.is_null(i) { result.push(None); } else { let slice = list_array.value(i); let primitive_slice = slice.as_any().downcast_ref::<PrimitiveArray<T>>().unwrap(); let max = primitive_slice.iter().flatten().max(); result.push(max); } } let array = PrimitiveArray::<T>::from_iter(result); Ok(ColumnarValue::Array(Arc::new(array))) } -- 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. 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