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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/01/25 07:10:03 UTC
[GitHub] [arrow] jorgecarleitao commented on a change in pull request #9256: WIP: ARROW-11310: [Rust] implement JSON writer
jorgecarleitao commented on a change in pull request #9256:
URL: https://github.com/apache/arrow/pull/9256#discussion_r563499210
##########
File path: rust/arrow/src/json/writer.rs
##########
@@ -0,0 +1,301 @@
+// 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.
+
+//! JSON Writer
+//!
+//! This JSON writer allows converting Arrow record batches into array of JSON objects. It also
+//! provides a Writer struct to help serialize record batches directly into line-delimited JSON
+//! objects as bytes.
+//!
+//! Serialize record batches into array of JSON objects:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let json_rows = json::writer::record_batches_to_json_rows(&[batch]);
+//! assert_eq!(
+//! serde_json::Value::Object(json_rows[1].clone()),
+//! serde_json::json!({"a": 2}),
+//! );
+//! ```
+//!
+//! Serialize record batches into line-delimited JSON bytes:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let buf = Vec::new();
+//! let mut writer = json::Writer::new(buf);
+//! writer.write_batches(&vec![batch]).unwrap();
+//! ```
+
+use std::io::{BufWriter, Write};
+use std::iter;
+
+use serde_json::map::Map as JsonMap;
+use serde_json::Value;
+
+use crate::array::*;
+use crate::datatypes::*;
+use crate::error::Result;
+use crate::record_batch::RecordBatch;
+
+fn set_column_by_primitive_type<T: ArrowPrimitiveType>(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ let primitive_arr = as_primitive_array::<T>(array);
+ for (i, row) in rows.iter_mut().enumerate().take(row_count) {
+ row.insert(
+ col_name.to_string(),
+ primitive_arr
+ .value(i)
+ .into_json_value()
+ .unwrap_or(Value::Null),
+ );
+ }
+}
+
+fn set_column_for_json_rows(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ match array.data_type() {
+ DataType::Null => {
+ for row in rows.iter_mut().take(row_count) {
+ row.insert(col_name.to_string(), Value::Null);
+ }
+ }
+ DataType::Boolean => {
+ let arr = as_boolean_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), arr.value(i).into());
Review comment:
Same here. Try using `arr.iter()`
##########
File path: rust/arrow/src/json/writer.rs
##########
@@ -0,0 +1,301 @@
+// 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.
+
+//! JSON Writer
+//!
+//! This JSON writer allows converting Arrow record batches into array of JSON objects. It also
+//! provides a Writer struct to help serialize record batches directly into line-delimited JSON
+//! objects as bytes.
+//!
+//! Serialize record batches into array of JSON objects:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let json_rows = json::writer::record_batches_to_json_rows(&[batch]);
+//! assert_eq!(
+//! serde_json::Value::Object(json_rows[1].clone()),
+//! serde_json::json!({"a": 2}),
+//! );
+//! ```
+//!
+//! Serialize record batches into line-delimited JSON bytes:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let buf = Vec::new();
+//! let mut writer = json::Writer::new(buf);
+//! writer.write_batches(&vec![batch]).unwrap();
+//! ```
+
+use std::io::{BufWriter, Write};
+use std::iter;
+
+use serde_json::map::Map as JsonMap;
+use serde_json::Value;
+
+use crate::array::*;
+use crate::datatypes::*;
+use crate::error::Result;
+use crate::record_batch::RecordBatch;
+
+fn set_column_by_primitive_type<T: ArrowPrimitiveType>(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ let primitive_arr = as_primitive_array::<T>(array);
+ for (i, row) in rows.iter_mut().enumerate().take(row_count) {
+ row.insert(
+ col_name.to_string(),
+ primitive_arr
+ .value(i)
Review comment:
This won't take nulls into account.
One way to go here is to use
```rust
rows.iter_mut().zip(primitive_arr.iter()).take(row_count).for_each(|(row, maybe_value)| {
...
})
```
`maybe_value` will be of type `Option<T::Native>`, where `None` represents a null value.
##########
File path: rust/arrow/src/json/writer.rs
##########
@@ -0,0 +1,301 @@
+// 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.
+
+//! JSON Writer
+//!
+//! This JSON writer allows converting Arrow record batches into array of JSON objects. It also
+//! provides a Writer struct to help serialize record batches directly into line-delimited JSON
+//! objects as bytes.
+//!
+//! Serialize record batches into array of JSON objects:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let json_rows = json::writer::record_batches_to_json_rows(&[batch]);
+//! assert_eq!(
+//! serde_json::Value::Object(json_rows[1].clone()),
+//! serde_json::json!({"a": 2}),
+//! );
+//! ```
+//!
+//! Serialize record batches into line-delimited JSON bytes:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let buf = Vec::new();
+//! let mut writer = json::Writer::new(buf);
+//! writer.write_batches(&vec![batch]).unwrap();
+//! ```
+
+use std::io::{BufWriter, Write};
+use std::iter;
+
+use serde_json::map::Map as JsonMap;
+use serde_json::Value;
+
+use crate::array::*;
+use crate::datatypes::*;
+use crate::error::Result;
+use crate::record_batch::RecordBatch;
+
+fn set_column_by_primitive_type<T: ArrowPrimitiveType>(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ let primitive_arr = as_primitive_array::<T>(array);
+ for (i, row) in rows.iter_mut().enumerate().take(row_count) {
+ row.insert(
+ col_name.to_string(),
+ primitive_arr
+ .value(i)
+ .into_json_value()
+ .unwrap_or(Value::Null),
+ );
+ }
+}
+
+fn set_column_for_json_rows(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ match array.data_type() {
+ DataType::Null => {
+ for row in rows.iter_mut().take(row_count) {
+ row.insert(col_name.to_string(), Value::Null);
+ }
+ }
+ DataType::Boolean => {
+ let arr = as_boolean_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), arr.value(i).into());
+ }
+ }
+ DataType::Int8 => {
+ set_column_by_primitive_type::<Int8Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int16 => {
+ set_column_by_primitive_type::<Int16Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int32 => {
+ set_column_by_primitive_type::<Int32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int64 => {
+ set_column_by_primitive_type::<Int64Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt8 => {
+ set_column_by_primitive_type::<UInt8Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt16 => {
+ set_column_by_primitive_type::<UInt16Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt32 => {
+ set_column_by_primitive_type::<UInt32Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt64 => {
+ set_column_by_primitive_type::<UInt64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float32 => {
+ set_column_by_primitive_type::<Float32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float64 => {
+ set_column_by_primitive_type::<Float64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Utf8 => {
+ let strarr = as_string_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), strarr.value(i).into());
+ }
+ }
+ DataType::Struct(_) => {
+ let arr = as_struct_array(array);
+ let inner_col_names = arr.column_names();
+
+ let mut inner_objs = iter::repeat(JsonMap::new())
+ .take(row_count)
+ .collect::<Vec<JsonMap<String, Value>>>();
+
+ arr.columns()
+ .iter()
+ .enumerate()
+ .for_each(|(j, struct_col)| {
+ set_column_for_json_rows(
+ &mut inner_objs,
+ row_count,
+ struct_col,
+ inner_col_names[j],
+ );
+ });
+
+ rows.iter_mut()
+ .take(row_count)
+ .zip(inner_objs.into_iter())
+ .for_each(|(row, obj)| {
+ row.insert(col_name.to_string(), Value::Object(obj));
+ });
+ }
+ _ => {
+ panic!(format!("Unsupported datatype: {:#?}", array.data_type()));
+ }
+ }
+}
+
+pub fn record_batches_to_json_rows(
+ batches: &[RecordBatch],
+) -> Vec<JsonMap<String, Value>> {
+ let mut rows: Vec<JsonMap<String, Value>> = iter::repeat(JsonMap::new())
+ .take(batches.iter().map(|b| b.num_rows()).sum())
+ .collect();
+
+ if !rows.is_empty() {
+ let schema = batches[0].schema();
+ let mut base = 0;
+ batches.iter().for_each(|batch| {
+ let row_count = batch.num_rows();
+ batch.columns().iter().enumerate().for_each(|(j, col)| {
+ let col_name = schema.field(j).name();
+ set_column_for_json_rows(&mut rows[base..], row_count, col, col_name);
+ });
+ base += row_count;
+ });
+ }
+
+ rows
+}
+
+/// A JSON writer
+#[derive(Debug)]
+pub struct Writer<W: Write> {
+ writer: BufWriter<W>,
+}
+
+impl<W: Write> Writer<W> {
+ pub fn new(writer: W) -> Self {
+ Self::from_buf_writer(BufWriter::new(writer))
+ }
+
+ pub fn from_buf_writer(writer: BufWriter<W>) -> Self {
+ Self { writer }
+ }
+
+ pub fn write_row(&mut self, row: &Value) -> Result<()> {
+ self.writer.write_all(&serde_json::to_vec(row)?)?;
+ self.writer.write_all(b"\n")?;
+ Ok(())
+ }
+
+ pub fn write_batches(&mut self, batches: &[RecordBatch]) -> Result<()> {
+ for row in record_batches_to_json_rows(batches) {
+ self.write_row(&Value::Object(row))?;
+ }
+ Ok(())
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use std::fs::{read_to_string, File};
+ use std::sync::Arc;
+
+ use crate::json::reader::*;
+
+ use super::*;
+
+ #[test]
+ fn write_simple_rows() {
+ let schema = Schema::new(vec![
+ Field::new("a", DataType::Int32, false),
+ Field::new("b", DataType::Utf8, false),
+ ]);
+
+ let a = Int32Array::from(vec![1, 2, 3, 4, 5]);
Review comment:
could have use `vec![Some(1), None, Some(3), Some(4,) Some(5)]`, so that we also test null values?
##########
File path: rust/arrow/src/json/writer.rs
##########
@@ -0,0 +1,301 @@
+// 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.
+
+//! JSON Writer
+//!
+//! This JSON writer allows converting Arrow record batches into array of JSON objects. It also
+//! provides a Writer struct to help serialize record batches directly into line-delimited JSON
+//! objects as bytes.
+//!
+//! Serialize record batches into array of JSON objects:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let json_rows = json::writer::record_batches_to_json_rows(&[batch]);
+//! assert_eq!(
+//! serde_json::Value::Object(json_rows[1].clone()),
+//! serde_json::json!({"a": 2}),
+//! );
+//! ```
+//!
+//! Serialize record batches into line-delimited JSON bytes:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let buf = Vec::new();
+//! let mut writer = json::Writer::new(buf);
+//! writer.write_batches(&vec![batch]).unwrap();
+//! ```
+
+use std::io::{BufWriter, Write};
+use std::iter;
+
+use serde_json::map::Map as JsonMap;
+use serde_json::Value;
+
+use crate::array::*;
+use crate::datatypes::*;
+use crate::error::Result;
+use crate::record_batch::RecordBatch;
+
+fn set_column_by_primitive_type<T: ArrowPrimitiveType>(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ let primitive_arr = as_primitive_array::<T>(array);
+ for (i, row) in rows.iter_mut().enumerate().take(row_count) {
+ row.insert(
+ col_name.to_string(),
+ primitive_arr
+ .value(i)
+ .into_json_value()
+ .unwrap_or(Value::Null),
+ );
+ }
+}
+
+fn set_column_for_json_rows(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ match array.data_type() {
+ DataType::Null => {
+ for row in rows.iter_mut().take(row_count) {
+ row.insert(col_name.to_string(), Value::Null);
+ }
+ }
+ DataType::Boolean => {
+ let arr = as_boolean_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), arr.value(i).into());
+ }
+ }
+ DataType::Int8 => {
+ set_column_by_primitive_type::<Int8Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int16 => {
+ set_column_by_primitive_type::<Int16Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int32 => {
+ set_column_by_primitive_type::<Int32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int64 => {
+ set_column_by_primitive_type::<Int64Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt8 => {
+ set_column_by_primitive_type::<UInt8Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt16 => {
+ set_column_by_primitive_type::<UInt16Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt32 => {
+ set_column_by_primitive_type::<UInt32Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt64 => {
+ set_column_by_primitive_type::<UInt64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float32 => {
+ set_column_by_primitive_type::<Float32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float64 => {
+ set_column_by_primitive_type::<Float64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Utf8 => {
+ let strarr = as_string_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), strarr.value(i).into());
Review comment:
same here.
##########
File path: rust/arrow/src/json/writer.rs
##########
@@ -0,0 +1,301 @@
+// 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.
+
+//! JSON Writer
+//!
+//! This JSON writer allows converting Arrow record batches into array of JSON objects. It also
+//! provides a Writer struct to help serialize record batches directly into line-delimited JSON
+//! objects as bytes.
+//!
+//! Serialize record batches into array of JSON objects:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let json_rows = json::writer::record_batches_to_json_rows(&[batch]);
+//! assert_eq!(
+//! serde_json::Value::Object(json_rows[1].clone()),
+//! serde_json::json!({"a": 2}),
+//! );
+//! ```
+//!
+//! Serialize record batches into line-delimited JSON bytes:
+//!
+//! ```
+//! use std::sync::Arc;
+//!
+//! use arrow::array::Int32Array;
+//! use arrow::datatypes::{DataType, Field, Schema};
+//! use arrow::json;
+//! use arrow::record_batch::RecordBatch;
+//!
+//! let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
+//! let a = Int32Array::from(vec![1, 2, 3]);
+//! let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
+//!
+//! let buf = Vec::new();
+//! let mut writer = json::Writer::new(buf);
+//! writer.write_batches(&vec![batch]).unwrap();
+//! ```
+
+use std::io::{BufWriter, Write};
+use std::iter;
+
+use serde_json::map::Map as JsonMap;
+use serde_json::Value;
+
+use crate::array::*;
+use crate::datatypes::*;
+use crate::error::Result;
+use crate::record_batch::RecordBatch;
+
+fn set_column_by_primitive_type<T: ArrowPrimitiveType>(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ let primitive_arr = as_primitive_array::<T>(array);
+ for (i, row) in rows.iter_mut().enumerate().take(row_count) {
+ row.insert(
+ col_name.to_string(),
+ primitive_arr
+ .value(i)
+ .into_json_value()
+ .unwrap_or(Value::Null),
+ );
+ }
+}
+
+fn set_column_for_json_rows(
+ rows: &mut [JsonMap<String, Value>],
+ row_count: usize,
+ array: &ArrayRef,
+ col_name: &str,
+) {
+ match array.data_type() {
+ DataType::Null => {
+ for row in rows.iter_mut().take(row_count) {
+ row.insert(col_name.to_string(), Value::Null);
+ }
+ }
+ DataType::Boolean => {
+ let arr = as_boolean_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), arr.value(i).into());
+ }
+ }
+ DataType::Int8 => {
+ set_column_by_primitive_type::<Int8Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int16 => {
+ set_column_by_primitive_type::<Int16Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int32 => {
+ set_column_by_primitive_type::<Int32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Int64 => {
+ set_column_by_primitive_type::<Int64Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt8 => {
+ set_column_by_primitive_type::<UInt8Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt16 => {
+ set_column_by_primitive_type::<UInt16Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt32 => {
+ set_column_by_primitive_type::<UInt32Type>(rows, row_count, array, col_name)
+ }
+ DataType::UInt64 => {
+ set_column_by_primitive_type::<UInt64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float32 => {
+ set_column_by_primitive_type::<Float32Type>(rows, row_count, array, col_name)
+ }
+ DataType::Float64 => {
+ set_column_by_primitive_type::<Float64Type>(rows, row_count, array, col_name)
+ }
+ DataType::Utf8 => {
+ let strarr = as_string_array(array);
+ for (i, row) in rows.iter_mut().take(row_count).enumerate() {
+ row.insert(col_name.to_string(), strarr.value(i).into());
+ }
+ }
+ DataType::Struct(_) => {
+ let arr = as_struct_array(array);
+ let inner_col_names = arr.column_names();
+
+ let mut inner_objs = iter::repeat(JsonMap::new())
+ .take(row_count)
+ .collect::<Vec<JsonMap<String, Value>>>();
+
+ arr.columns()
+ .iter()
+ .enumerate()
+ .for_each(|(j, struct_col)| {
+ set_column_for_json_rows(
+ &mut inner_objs,
+ row_count,
+ struct_col,
+ inner_col_names[j],
+ );
+ });
+
+ rows.iter_mut()
+ .take(row_count)
+ .zip(inner_objs.into_iter())
+ .for_each(|(row, obj)| {
+ row.insert(col_name.to_string(), Value::Object(obj));
+ });
+ }
+ _ => {
+ panic!(format!("Unsupported datatype: {:#?}", array.data_type()));
+ }
+ }
+}
+
+pub fn record_batches_to_json_rows(
+ batches: &[RecordBatch],
+) -> Vec<JsonMap<String, Value>> {
+ let mut rows: Vec<JsonMap<String, Value>> = iter::repeat(JsonMap::new())
+ .take(batches.iter().map(|b| b.num_rows()).sum())
+ .collect();
+
+ if !rows.is_empty() {
+ let schema = batches[0].schema();
+ let mut base = 0;
+ batches.iter().for_each(|batch| {
+ let row_count = batch.num_rows();
+ batch.columns().iter().enumerate().for_each(|(j, col)| {
+ let col_name = schema.field(j).name();
+ set_column_for_json_rows(&mut rows[base..], row_count, col, col_name);
+ });
+ base += row_count;
+ });
+ }
+
+ rows
+}
+
+/// A JSON writer
+#[derive(Debug)]
+pub struct Writer<W: Write> {
+ writer: BufWriter<W>,
+}
+
+impl<W: Write> Writer<W> {
+ pub fn new(writer: W) -> Self {
+ Self::from_buf_writer(BufWriter::new(writer))
+ }
+
+ pub fn from_buf_writer(writer: BufWriter<W>) -> Self {
+ Self { writer }
+ }
+
+ pub fn write_row(&mut self, row: &Value) -> Result<()> {
+ self.writer.write_all(&serde_json::to_vec(row)?)?;
+ self.writer.write_all(b"\n")?;
+ Ok(())
+ }
+
+ pub fn write_batches(&mut self, batches: &[RecordBatch]) -> Result<()> {
+ for row in record_batches_to_json_rows(batches) {
+ self.write_row(&Value::Object(row))?;
+ }
+ Ok(())
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use std::fs::{read_to_string, File};
+ use std::sync::Arc;
+
+ use crate::json::reader::*;
+
+ use super::*;
+
+ #[test]
+ fn write_simple_rows() {
+ let schema = Schema::new(vec![
+ Field::new("a", DataType::Int32, false),
+ Field::new("b", DataType::Utf8, false),
+ ]);
+
+ let a = Int32Array::from(vec![1, 2, 3, 4, 5]);
+ let b = StringArray::from(vec!["a", "b", "c", "d", "e"]);
+
+ let batch =
+ RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a), Arc::new(b)])
+ .unwrap();
+
+ let mut buf = Vec::new();
+ {
+ let mut writer = Writer::new(&mut buf);
+ writer.write_batches(&vec![batch]).unwrap();
+ }
+
+ assert_eq!(
+ String::from_utf8(buf).unwrap(),
+ r#"{"a":1,"b":"a"}
+{"a":2,"b":"b"}
+{"a":3,"b":"c"}
+{"a":4,"b":"d"}
+{"a":5,"b":"e"}
+"#
+ );
+ }
+
+ fn test_write_for_file(test_file: &str) {
+ let builder = ReaderBuilder::new()
+ .infer_schema(None)
+ .with_batch_size(1024);
+ let mut reader: Reader<File> = builder
+ .build::<File>(File::open(test_file).unwrap())
+ .unwrap();
+ let batch = reader.next().unwrap().unwrap();
+
+ let mut buf = Vec::new();
+ {
+ let mut writer = Writer::new(&mut buf);
+ writer.write_batches(&vec![batch]).unwrap();
+ }
+
+ let result = String::from_utf8(buf).unwrap();
+ let expected = read_to_string(test_file).unwrap();
+ for (r, e) in result.lines().zip(expected.lines()) {
+ assert_eq!(
+ serde_json::from_str::<Value>(r).unwrap(),
+ serde_json::from_str::<Value>(e).unwrap()
+ );
+ }
+ }
+
+ #[test]
+ fn write_basic_rows() {
+ test_write_for_file("test/data/basic.json");
Review comment:
AFAI understand this will populate a file and not delete it at the end.
Would it be possible to write to a byte stream or something instead of a file? Alternatively, use `tmp` or something?
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