gstvg commented on code in PR #21679: URL: https://github.com/apache/datafusion/pull/21679#discussion_r3135646631
########## datafusion/functions-nested/src/array_transform.rs: ########## @@ -0,0 +1,457 @@ +// 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. + +//! [`HigherOrderUDF`] definitions for array_transform function. + +use arrow::{ + array::{ + Array, ArrayRef, AsArray, FixedSizeListArray, LargeListArray, ListArray, + new_null_array, + }, + datatypes::{DataType, Field, FieldRef}, +}; +use datafusion_common::{ + Result, exec_err, plan_err, + utils::{adjust_offsets_for_slice, list_values, take_function_args}, +}; +use datafusion_expr::{ + ColumnarValue, Documentation, HigherOrderFunctionArgs, HigherOrderReturnFieldArgs, + HigherOrderSignature, HigherOrderUDF, ValueOrLambda, Volatility, +}; +use datafusion_macros::user_doc; +use std::{fmt::Debug, sync::Arc}; + +make_udhof_expr_and_func!( + ArrayTransform, + array_transform, + array lambda, + "transforms the values of an array", + array_transform_udhof +); + +#[user_doc( + doc_section(label = "Array Functions"), + description = "transforms the values of an array", + syntax_example = "array_transform(array, x -> x*2)", + sql_example = r#"```sql +> select array_transform([1, 2, 3, 4, 5], x -> x*2); ++-------------------------------------------+ +| array_transform([1, 2, 3, 4, 5], x -> x*2) | ++-------------------------------------------+ +| [2, 4, 6, 8, 10] | ++-------------------------------------------+ +```"#, + argument( + name = "array", + description = "Array expression. Can be a constant, column, or function, and any combination of array operators." + ), + argument(name = "lambda", description = "Lambda") +)] +#[derive(Debug, PartialEq, Eq, Hash)] +pub struct ArrayTransform { + signature: HigherOrderSignature, + aliases: Vec<String>, +} + +impl Default for ArrayTransform { + fn default() -> Self { + Self::new() + } +} + +impl ArrayTransform { + pub fn new() -> Self { + Self { + signature: HigherOrderSignature::user_defined(Volatility::Immutable), + aliases: vec![String::from("list_transform")], + } + } +} + +impl HigherOrderUDF for ArrayTransform { + fn name(&self) -> &str { + "array_transform" + } + + fn aliases(&self) -> &[String] { + &self.aliases + } + + fn signature(&self) -> &HigherOrderSignature { + &self.signature + } + + fn coerce_value_types(&self, arg_types: &[DataType]) -> Result<Vec<DataType>> { + let list = if arg_types.len() == 1 { + &arg_types[0] + } else { + return plan_err!( + "{} function requires 1 value arguments, got {}", + self.name(), + arg_types.len() + ); + }; + + let coerced = match list { + DataType::List(_) + | DataType::LargeList(_) + | DataType::FixedSizeList(_, _) => list.clone(), + DataType::ListView(field) => DataType::List(Arc::clone(field)), + DataType::LargeListView(field) => DataType::LargeList(Arc::clone(field)), + _ => { + return plan_err!( + "{} expected a list as first argument, got {}", + self.name(), + list + ); + } + }; + + Ok(vec![coerced]) + } + + fn lambda_parameters(&self, value_fields: &[FieldRef]) -> Result<Vec<Vec<Field>>> { + let list = if value_fields.len() == 1 { + &value_fields[0] + } else { + return plan_err!( + "{} function requires 1 value arguments, got {}", + self.name(), + value_fields.len() + ); + }; + + let field = match list.data_type() { + DataType::List(field) => field, + DataType::LargeList(field) => field, + DataType::FixedSizeList(field, _) => field, + _ => return plan_err!("expected list, got {list}"), + }; + + // we don't need to check whether the lambda contains more than two parameters, + // e.g. array_transform([], (v, i, j) -> v+i+j), as datafusion will do that for us + let value = Field::new("", field.data_type().clone(), field.is_nullable()) + .with_metadata(field.metadata().clone()); Review Comment: Was being overzealous to avoid anyone from relying on the name being the list field *recommended* name (`item`), fixed at https://github.com/apache/datafusion/pull/21679/changes/9a83018838cefda0a51bd7dd708e85dcc63c8b31#diff-e464d894d5a0fe37392c40f9e54f67590220578259a8dc41fa57b329f6f0d343R142-R144 https://github.com/apache/datafusion/blob/9a83018838cefda0a51bd7dd708e85dcc63c8b31/datafusion/functions-nested/src/array_transform.rs#L135-L144 Note: I'll change this to FieldRef on another commit to not add noise to your reviewed code -- This is an automated message from the Apache Git Service. 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