andygrove commented on code in PR #805: URL: https://github.com/apache/datafusion-comet/pull/805#discussion_r1731420219
########## native/spark-expr/src/to_json.rs: ########## @@ -0,0 +1,295 @@ +// 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. + +// TODO upstream this to DataFusion as long as we have a way to specify all +// of the Spark-specific compatibility features that we need (including +// being able to specify Spark-compatible cast from all types to string) + +use crate::{spark_cast, EvalMode}; +use arrow_array::builder::StringBuilder; +use arrow_array::{Array, ArrayRef, RecordBatch, StringArray, StructArray}; +use arrow_schema::{DataType, Schema}; +use datafusion_common::Result; +use datafusion_expr::ColumnarValue; +use datafusion_physical_expr_common::physical_expr::PhysicalExpr; +use std::any::Any; +use std::fmt::{Debug, Display, Formatter}; +use std::hash::{Hash, Hasher}; +use std::sync::Arc; + +/// to_json function +#[derive(Debug, Hash)] +pub struct ToJson { + /// The input to convert to JSON + expr: Arc<dyn PhysicalExpr>, + /// Timezone to use when converting timestamps to JSON + timezone: String, +} + +impl ToJson { + pub fn new(expr: Arc<dyn PhysicalExpr>, timezone: &str) -> Self { + Self { + expr, + timezone: timezone.to_owned(), + } + } +} + +impl Display for ToJson { + fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result { + write!(f, "to_json({}, timezone={})", self.expr, self.timezone) + } +} + +impl PartialEq<dyn Any> for ToJson { + fn eq(&self, other: &dyn Any) -> bool { + if let Some(other) = other.downcast_ref::<ToJson>() { + self.expr.eq(&other.expr) && self.timezone.eq(&other.timezone) + } else { + false + } + } +} + +impl PhysicalExpr for ToJson { + fn as_any(&self) -> &dyn Any { + self + } + + fn data_type(&self, _: &Schema) -> Result<DataType> { + Ok(DataType::Utf8) + } + + fn nullable(&self, input_schema: &Schema) -> Result<bool> { + self.expr.nullable(input_schema) + } + + fn evaluate(&self, batch: &RecordBatch) -> Result<ColumnarValue> { + let input = self.expr.evaluate(batch)?.into_array(batch.num_rows())?; + Ok(ColumnarValue::Array(array_to_json_string( + &input, + &self.timezone, + )?)) + } + + fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>> { + vec![&self.expr] + } + + fn with_new_children( + self: Arc<Self>, + children: Vec<Arc<dyn PhysicalExpr>>, + ) -> Result<Arc<dyn PhysicalExpr>> { + assert!(children.len() == 1); + Ok(Arc::new(Self::new(children[0].clone(), &self.timezone))) + } + + fn dyn_hash(&self, state: &mut dyn Hasher) { + let mut s = state; + self.expr.hash(&mut s); + self.timezone.hash(&mut s); + self.hash(&mut s); + } +} + +/// Convert an array into a JSON value string representation +fn array_to_json_string(arr: &Arc<dyn Array>, timezone: &str) -> Result<ArrayRef> { + if let Some(struct_array) = arr.as_any().downcast_ref::<StructArray>() { + struct_to_json(struct_array, timezone) + } else { + spark_cast( + ColumnarValue::Array(Arc::clone(arr)), + &DataType::Utf8, + EvalMode::Legacy, + timezone, + )? + .into_array(arr.len()) + } +} + +fn struct_to_json(array: &StructArray, timezone: &str) -> Result<ArrayRef> { + // get field names + let field_names: Vec<String> = array.fields().iter().map(|f| f.name().clone()).collect(); + // determine which fields need to have their values quoted + let quotes_needed: Vec<bool> = array + .fields() + .iter() + .map(|f| match f.data_type() { + DataType::Utf8 | DataType::LargeUtf8 => true, + DataType::Dictionary(_, dt) => { + matches!(dt.as_ref(), DataType::Utf8 | DataType::LargeUtf8) + } + _ => false, + }) + .collect(); + // create JSON string representation of each column + let string_arrays: Vec<ArrayRef> = array + .columns() + .iter() + .map(|arr| array_to_json_string(arr, timezone)) + .collect::<Result<Vec<_>>>()?; + let string_arrays: Vec<&StringArray> = string_arrays + .iter() + .map(|arr| { + arr.as_any() + .downcast_ref::<StringArray>() + .expect("string array") + }) + .collect(); + // build the JSON string containing entries in the format `"field_name":field_value` + let mut builder = StringBuilder::with_capacity(array.len(), array.len() * 16); + let mut json = String::with_capacity(array.len() * 16); + for row_index in 0..array.len() { + if array.is_null(row_index) { + builder.append_null(); + } else { + json.clear(); + let mut any_fields_written = false; + json.push('{'); + for col_index in 0..string_arrays.len() { + if !string_arrays[col_index].is_null(row_index) { + if any_fields_written { + json.push(','); + } + // quoted field name + json.push('"'); + json.push_str(&field_names[col_index]); + json.push_str("\":"); + // value + if quotes_needed[col_index] { + json.push('"'); + } + json.push_str(string_arrays[col_index].value(row_index)); + if quotes_needed[col_index] { + json.push('"'); + } Review Comment: I have now added escaping for common cases such as \t \r \n \b \f and double quotes -- This is an automated message from the Apache Git Service. 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