Module arrow::json::writer [−][src]
Expand description
JSON Writer
This JSON writer converts Arrow RecordBatch
es into arrays of
JSON objects or JSON formatted byte streams.
Writing JSON Objects
To serialize RecordBatch
es into array of
JSON objects, use
record_batches_to_json_rows
:
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}), );
Writing JSON formatted byte streams
To serialize RecordBatch
es into line-delimited JSON bytes, use
LineDelimitedWriter
:
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(); // Write the record batch out as JSON let buf = Vec::new(); let mut writer = json::LineDelimitedWriter::new(buf); writer.write_batches(&vec![batch]).unwrap(); writer.finish().unwrap(); // Get the underlying buffer back, let buf = writer.into_inner(); assert_eq!(r#"{"a":1} {"a":2} {"a":3} "#, String::from_utf8(buf).unwrap())
To serialize RecordBatch
es into a well formed JSON array, use
ArrayWriter
:
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(); // Write the record batch out as a JSON array let buf = Vec::new(); let mut writer = json::ArrayWriter::new(buf); writer.write_batches(&vec![batch]).unwrap(); writer.finish().unwrap(); // Get the underlying buffer back, let buf = writer.into_inner(); assert_eq!(r#"[{"a":1},{"a":2},{"a":3}]"#, String::from_utf8(buf).unwrap())
Structs
JsonArray | Produces JSON output as a single JSON array. For example |
LineDelimited | Produces JSON output with one record per line. For example |
Writer | A JSON writer which serializes |
Traits
JsonFormat | This trait defines how to format a sequence of JSON objects to a byte stream. |
Functions
array_to_json_array | Converts an arrow |
record_batches_to_json_rows | Converts an arrow |
Type Definitions
ArrayWriter | A JSON writer which serializes |
LineDelimitedWriter | A JSON writer which serializes |