parquet/arrow/async_writer/
mod.rs

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16// under the License.
17
18//! `async` API for writing [`RecordBatch`]es to Parquet files
19//!
20//! See the [crate-level documentation](crate) for more details.
21//!
22//! The `async` API for writing [`RecordBatch`]es is
23//! similar to the [`sync` API](ArrowWriter), so please
24//! read the documentation there before using this API.
25//!
26//! Here is an example for using [`AsyncArrowWriter`]:
27//!
28//! ```
29//! # #[tokio::main(flavor="current_thread")]
30//! # async fn main() {
31//! #
32//! # use std::sync::Arc;
33//! # use arrow_array::{ArrayRef, Int64Array, RecordBatch, RecordBatchReader};
34//! # use bytes::Bytes;
35//! # use parquet::arrow::{AsyncArrowWriter, arrow_reader::ParquetRecordBatchReaderBuilder};
36//! #
37//! let col = Arc::new(Int64Array::from_iter_values([1, 2, 3])) as ArrayRef;
38//! let to_write = RecordBatch::try_from_iter([("col", col)]).unwrap();
39//!
40//! let mut buffer = Vec::new();
41//! let mut writer = AsyncArrowWriter::try_new(&mut buffer, to_write.schema(), None).unwrap();
42//! writer.write(&to_write).await.unwrap();
43//! writer.close().await.unwrap();
44//!
45//! let buffer = Bytes::from(buffer);
46//! let mut reader = ParquetRecordBatchReaderBuilder::try_new(buffer.clone())
47//!     .unwrap()
48//!     .build()
49//!     .unwrap();
50//! let read = reader.next().unwrap().unwrap();
51//!
52//! assert_eq!(to_write, read);
53//! # }
54//! ```
55//!
56//! [`object_store`] provides it's native implementation of [`AsyncFileWriter`] by [`ParquetObjectWriter`].
57
58#[cfg(feature = "object_store")]
59mod store;
60#[cfg(feature = "object_store")]
61pub use store::*;
62
63use crate::{
64    arrow::arrow_writer::ArrowWriterOptions,
65    arrow::ArrowWriter,
66    errors::{ParquetError, Result},
67    file::{metadata::RowGroupMetaData, properties::WriterProperties},
68    format::{FileMetaData, KeyValue},
69};
70use arrow_array::RecordBatch;
71use arrow_schema::SchemaRef;
72use bytes::Bytes;
73use futures::future::BoxFuture;
74use futures::FutureExt;
75use std::mem;
76use tokio::io::{AsyncWrite, AsyncWriteExt};
77
78/// The asynchronous interface used by [`AsyncArrowWriter`] to write parquet files.
79pub trait AsyncFileWriter: Send {
80    /// Write the provided bytes to the underlying writer
81    ///
82    /// The underlying writer CAN decide to buffer the data or write it immediately.
83    /// This design allows the writer implementer to control the buffering and I/O scheduling.
84    ///
85    /// The underlying writer MAY implement retry logic to prevent breaking users write process.
86    fn write(&mut self, bs: Bytes) -> BoxFuture<'_, Result<()>>;
87
88    /// Flush any buffered data to the underlying writer and finish writing process.
89    ///
90    /// After `complete` returns `Ok(())`, caller SHOULD not call write again.
91    fn complete(&mut self) -> BoxFuture<'_, Result<()>>;
92}
93
94impl AsyncFileWriter for Box<dyn AsyncFileWriter + '_> {
95    fn write(&mut self, bs: Bytes) -> BoxFuture<'_, Result<()>> {
96        self.as_mut().write(bs)
97    }
98
99    fn complete(&mut self) -> BoxFuture<'_, Result<()>> {
100        self.as_mut().complete()
101    }
102}
103
104impl<T: AsyncWrite + Unpin + Send> AsyncFileWriter for T {
105    fn write(&mut self, bs: Bytes) -> BoxFuture<'_, Result<()>> {
106        async move {
107            self.write_all(&bs).await?;
108            Ok(())
109        }
110        .boxed()
111    }
112
113    fn complete(&mut self) -> BoxFuture<'_, Result<()>> {
114        async move {
115            self.flush().await?;
116            self.shutdown().await?;
117            Ok(())
118        }
119        .boxed()
120    }
121}
122
123/// Encodes [`RecordBatch`] to parquet, outputting to an [`AsyncFileWriter`]
124///
125/// ## Memory Usage
126///
127/// This writer eagerly writes data as soon as possible to the underlying [`AsyncFileWriter`],
128/// permitting fine-grained control over buffering and I/O scheduling. However, the columnar
129/// nature of parquet forces data for an entire row group to be buffered in memory, before
130/// it can be flushed. Depending on the data and the configured row group size, this buffering
131/// may be substantial.
132///
133/// Memory usage can be limited by calling [`Self::flush`] to flush the in progress row group,
134/// although this will likely increase overall file size and reduce query performance.
135/// See [ArrowWriter] for more information.
136///
137/// ```no_run
138/// # use tokio::fs::File;
139/// # use arrow_array::RecordBatch;
140/// # use parquet::arrow::AsyncArrowWriter;
141/// # async fn test() {
142/// let mut writer: AsyncArrowWriter<File> = todo!();
143/// let batch: RecordBatch = todo!();
144/// writer.write(&batch).await.unwrap();
145/// // Trigger an early flush if buffered size exceeds 1_000_000
146/// if writer.in_progress_size() > 1_000_000 {
147///     writer.flush().await.unwrap()
148/// }
149/// # }
150/// ```
151pub struct AsyncArrowWriter<W> {
152    /// Underlying sync writer
153    sync_writer: ArrowWriter<Vec<u8>>,
154
155    /// Async writer provided by caller
156    async_writer: W,
157}
158
159impl<W: AsyncFileWriter> AsyncArrowWriter<W> {
160    /// Try to create a new Async Arrow Writer
161    pub fn try_new(
162        writer: W,
163        arrow_schema: SchemaRef,
164        props: Option<WriterProperties>,
165    ) -> Result<Self> {
166        let options = ArrowWriterOptions::new().with_properties(props.unwrap_or_default());
167        Self::try_new_with_options(writer, arrow_schema, options)
168    }
169
170    /// Try to create a new Async Arrow Writer with [`ArrowWriterOptions`]
171    pub fn try_new_with_options(
172        writer: W,
173        arrow_schema: SchemaRef,
174        options: ArrowWriterOptions,
175    ) -> Result<Self> {
176        let sync_writer = ArrowWriter::try_new_with_options(Vec::new(), arrow_schema, options)?;
177
178        Ok(Self {
179            sync_writer,
180            async_writer: writer,
181        })
182    }
183
184    /// Returns metadata for any flushed row groups
185    pub fn flushed_row_groups(&self) -> &[RowGroupMetaData] {
186        self.sync_writer.flushed_row_groups()
187    }
188
189    /// Estimated memory usage, in bytes, of this `ArrowWriter`
190    ///
191    /// See [ArrowWriter::memory_size] for more information.
192    pub fn memory_size(&self) -> usize {
193        self.sync_writer.memory_size()
194    }
195
196    /// Anticipated encoded size of the in progress row group.
197    ///
198    /// See [ArrowWriter::memory_size] for more information.
199    pub fn in_progress_size(&self) -> usize {
200        self.sync_writer.in_progress_size()
201    }
202
203    /// Returns the number of rows buffered in the in progress row group
204    pub fn in_progress_rows(&self) -> usize {
205        self.sync_writer.in_progress_rows()
206    }
207
208    /// Returns the number of bytes written by this instance
209    pub fn bytes_written(&self) -> usize {
210        self.sync_writer.bytes_written()
211    }
212
213    /// Enqueues the provided `RecordBatch` to be written
214    ///
215    /// After every sync write by the inner [ArrowWriter], the inner buffer will be
216    /// checked and flush if at least half full
217    pub async fn write(&mut self, batch: &RecordBatch) -> Result<()> {
218        let before = self.sync_writer.flushed_row_groups().len();
219        self.sync_writer.write(batch)?;
220        if before != self.sync_writer.flushed_row_groups().len() {
221            self.do_write().await?;
222        }
223        Ok(())
224    }
225
226    /// Flushes all buffered rows into a new row group
227    pub async fn flush(&mut self) -> Result<()> {
228        self.sync_writer.flush()?;
229        self.do_write().await?;
230
231        Ok(())
232    }
233
234    /// Append [`KeyValue`] metadata in addition to those in [`WriterProperties`]
235    ///
236    /// This method allows to append metadata after [`RecordBatch`]es are written.
237    pub fn append_key_value_metadata(&mut self, kv_metadata: KeyValue) {
238        self.sync_writer.append_key_value_metadata(kv_metadata);
239    }
240
241    /// Close and finalize the writer.
242    ///
243    /// All the data in the inner buffer will be force flushed.
244    ///
245    /// Unlike [`Self::close`] this does not consume self
246    ///
247    /// Attempting to write after calling finish will result in an error
248    pub async fn finish(&mut self) -> Result<FileMetaData> {
249        let metadata = self.sync_writer.finish()?;
250
251        // Force to flush the remaining data.
252        self.do_write().await?;
253        self.async_writer.complete().await?;
254
255        Ok(metadata)
256    }
257
258    /// Close and finalize the writer.
259    ///
260    /// All the data in the inner buffer will be force flushed.
261    pub async fn close(mut self) -> Result<FileMetaData> {
262        self.finish().await
263    }
264
265    /// Flush the data written by `sync_writer` into the `async_writer`
266    ///
267    /// # Notes
268    ///
269    /// This method will take the inner buffer from the `sync_writer` and write it into the
270    /// async writer. After the write, the inner buffer will be empty.
271    async fn do_write(&mut self) -> Result<()> {
272        let buffer = mem::take(self.sync_writer.inner_mut());
273
274        self.async_writer
275            .write(Bytes::from(buffer))
276            .await
277            .map_err(|e| ParquetError::External(Box::new(e)))?;
278
279        Ok(())
280    }
281}
282
283#[cfg(test)]
284mod tests {
285    use arrow::datatypes::{DataType, Field, Schema};
286    use arrow_array::{ArrayRef, BinaryArray, Int32Array, Int64Array, RecordBatchReader};
287    use bytes::Bytes;
288    use std::sync::Arc;
289    use tokio::pin;
290
291    use crate::arrow::arrow_reader::{ParquetRecordBatchReader, ParquetRecordBatchReaderBuilder};
292
293    use super::*;
294
295    fn get_test_reader() -> ParquetRecordBatchReader {
296        let testdata = arrow::util::test_util::parquet_test_data();
297        // This test file is large enough to generate multiple row groups.
298        let path = format!("{}/alltypes_tiny_pages_plain.parquet", testdata);
299        let original_data = Bytes::from(std::fs::read(path).unwrap());
300        ParquetRecordBatchReaderBuilder::try_new(original_data)
301            .unwrap()
302            .build()
303            .unwrap()
304    }
305
306    #[tokio::test]
307    async fn test_async_writer() {
308        let col = Arc::new(Int64Array::from_iter_values([1, 2, 3])) as ArrayRef;
309        let to_write = RecordBatch::try_from_iter([("col", col)]).unwrap();
310
311        let mut buffer = Vec::new();
312        let mut writer = AsyncArrowWriter::try_new(&mut buffer, to_write.schema(), None).unwrap();
313        writer.write(&to_write).await.unwrap();
314        writer.close().await.unwrap();
315
316        let buffer = Bytes::from(buffer);
317        let mut reader = ParquetRecordBatchReaderBuilder::try_new(buffer)
318            .unwrap()
319            .build()
320            .unwrap();
321        let read = reader.next().unwrap().unwrap();
322
323        assert_eq!(to_write, read);
324    }
325
326    // Read the data from the test file and write it by the async writer and sync writer.
327    // And then compares the results of the two writers.
328    #[tokio::test]
329    async fn test_async_writer_with_sync_writer() {
330        let reader = get_test_reader();
331
332        let write_props = WriterProperties::builder()
333            .set_max_row_group_size(64)
334            .build();
335
336        let mut async_buffer = Vec::new();
337        let mut async_writer = AsyncArrowWriter::try_new(
338            &mut async_buffer,
339            reader.schema(),
340            Some(write_props.clone()),
341        )
342        .unwrap();
343
344        let mut sync_buffer = Vec::new();
345        let mut sync_writer =
346            ArrowWriter::try_new(&mut sync_buffer, reader.schema(), Some(write_props)).unwrap();
347        for record_batch in reader {
348            let record_batch = record_batch.unwrap();
349            async_writer.write(&record_batch).await.unwrap();
350            sync_writer.write(&record_batch).unwrap();
351        }
352        sync_writer.close().unwrap();
353        async_writer.close().await.unwrap();
354
355        assert_eq!(sync_buffer, async_buffer);
356    }
357
358    struct TestAsyncSink {
359        sink: Vec<u8>,
360        min_accept_bytes: usize,
361        expect_total_bytes: usize,
362    }
363
364    impl AsyncWrite for TestAsyncSink {
365        fn poll_write(
366            self: std::pin::Pin<&mut Self>,
367            cx: &mut std::task::Context<'_>,
368            buf: &[u8],
369        ) -> std::task::Poll<std::result::Result<usize, std::io::Error>> {
370            let written_bytes = self.sink.len();
371            if written_bytes + buf.len() < self.expect_total_bytes {
372                assert!(buf.len() >= self.min_accept_bytes);
373            } else {
374                assert_eq!(written_bytes + buf.len(), self.expect_total_bytes);
375            }
376
377            let sink = &mut self.get_mut().sink;
378            pin!(sink);
379            sink.poll_write(cx, buf)
380        }
381
382        fn poll_flush(
383            self: std::pin::Pin<&mut Self>,
384            cx: &mut std::task::Context<'_>,
385        ) -> std::task::Poll<std::result::Result<(), std::io::Error>> {
386            let sink = &mut self.get_mut().sink;
387            pin!(sink);
388            sink.poll_flush(cx)
389        }
390
391        fn poll_shutdown(
392            self: std::pin::Pin<&mut Self>,
393            cx: &mut std::task::Context<'_>,
394        ) -> std::task::Poll<std::result::Result<(), std::io::Error>> {
395            let sink = &mut self.get_mut().sink;
396            pin!(sink);
397            sink.poll_shutdown(cx)
398        }
399    }
400
401    #[tokio::test]
402    async fn test_async_writer_bytes_written() {
403        let col = Arc::new(Int64Array::from_iter_values([1, 2, 3])) as ArrayRef;
404        let to_write = RecordBatch::try_from_iter([("col", col)]).unwrap();
405
406        let temp = tempfile::tempfile().unwrap();
407
408        let file = tokio::fs::File::from_std(temp.try_clone().unwrap());
409        let mut writer =
410            AsyncArrowWriter::try_new(file.try_clone().await.unwrap(), to_write.schema(), None)
411                .unwrap();
412        writer.write(&to_write).await.unwrap();
413        let _metadata = writer.finish().await.unwrap();
414        // After `finish` this should include the metadata and footer
415        let reported = writer.bytes_written();
416
417        // Get actual size from file metadata
418        let actual = file.metadata().await.unwrap().len() as usize;
419
420        assert_eq!(reported, actual);
421    }
422
423    #[tokio::test]
424    async fn test_async_writer_file() {
425        let col = Arc::new(Int64Array::from_iter_values([1, 2, 3])) as ArrayRef;
426        let col2 = Arc::new(BinaryArray::from_iter_values(vec![
427            vec![0; 500000],
428            vec![0; 500000],
429            vec![0; 500000],
430        ])) as ArrayRef;
431        let to_write = RecordBatch::try_from_iter([("col", col), ("col2", col2)]).unwrap();
432
433        let temp = tempfile::tempfile().unwrap();
434
435        let file = tokio::fs::File::from_std(temp.try_clone().unwrap());
436        let mut writer = AsyncArrowWriter::try_new(file, to_write.schema(), None).unwrap();
437        writer.write(&to_write).await.unwrap();
438        writer.close().await.unwrap();
439
440        let mut reader = ParquetRecordBatchReaderBuilder::try_new(temp)
441            .unwrap()
442            .build()
443            .unwrap();
444        let read = reader.next().unwrap().unwrap();
445
446        assert_eq!(to_write, read);
447    }
448
449    #[tokio::test]
450    async fn in_progress_accounting() {
451        // define schema
452        let schema = Schema::new(vec![Field::new("a", DataType::Int32, false)]);
453
454        // create some data
455        let a = Int32Array::from_value(0_i32, 512);
456
457        // build a record batch
458        let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap();
459
460        let temp = tempfile::tempfile().unwrap();
461        let file = tokio::fs::File::from_std(temp.try_clone().unwrap());
462        let mut writer = AsyncArrowWriter::try_new(file, batch.schema(), None).unwrap();
463
464        // starts empty
465        assert_eq!(writer.in_progress_size(), 0);
466        assert_eq!(writer.in_progress_rows(), 0);
467        assert_eq!(writer.bytes_written(), 4); // Initial Parquet header
468        writer.write(&batch).await.unwrap();
469
470        // updated on write
471        let initial_size = writer.in_progress_size();
472        assert!(initial_size > 0);
473        assert_eq!(writer.in_progress_rows(), batch.num_rows());
474        let initial_memory = writer.memory_size();
475        // memory estimate is larger than estimated encoded size
476        assert!(
477            initial_size <= initial_memory,
478            "{initial_size} <= {initial_memory}"
479        );
480
481        // updated on second write
482        writer.write(&batch).await.unwrap();
483        assert!(writer.in_progress_size() > initial_size);
484        assert_eq!(writer.in_progress_rows(), batch.num_rows() * 2);
485        assert!(writer.memory_size() > initial_memory);
486        assert!(
487            writer.in_progress_size() <= writer.memory_size(),
488            "in_progress_size {} <= memory_size {}",
489            writer.in_progress_size(),
490            writer.memory_size()
491        );
492
493        // in progress tracking is cleared, but the overall data written is updated
494        let pre_flush_bytes_written = writer.bytes_written();
495        writer.flush().await.unwrap();
496        assert_eq!(writer.in_progress_size(), 0);
497        assert_eq!(writer.memory_size(), 0);
498        assert_eq!(writer.in_progress_rows(), 0);
499        assert!(writer.bytes_written() > pre_flush_bytes_written);
500
501        writer.close().await.unwrap();
502    }
503}
parquet/arrow/async_writer/mod.rs

parquet/arrow/async_writer/
mod.rs
