IPC sink types and IPC file stream

Cargo.toml

@@ -134,7 +134,7 @@ io_csv_write = ["csv", "csv-core", "streaming-iterator", "lexical-core"]
 io_json = ["serde", "serde_json", "streaming-iterator", "fallible-streaming-iterator", "indexmap", "lexical-core"]
 io_ipc = ["arrow-format"]
 io_ipc_write_async = ["io_ipc", "futures"]
-io_ipc_read_async = ["io_ipc", "futures"]
+io_ipc_read_async = ["io_ipc", "futures", "async-stream"]
 io_ipc_compression = ["lz4", "zstd"]
 io_flight = ["io_ipc", "arrow-format/flight-data"]
 # base64 + io_ipc because arrow schemas are stored as base64-encoded ipc format.

src/io/ipc/read/file_async.rs

@@ -0,0 +1,275 @@
+//! Async reader for Arrow IPC files
+use std::io::SeekFrom;
+use std::sync::Arc;
+
+use arrow_format::ipc::{
+    planus::{ReadAsRoot, Vector},
+    BlockRef, FooterRef, MessageHeaderRef, MessageRef,
+};
+use futures::{
+    stream::BoxStream, AsyncRead, AsyncReadExt, AsyncSeek, AsyncSeekExt, Stream, StreamExt,
+};
+
+use crate::array::*;
+use crate::chunk::Chunk;
+use crate::datatypes::{Field, Schema};
+use crate::error::{ArrowError, Result};
+use crate::io::ipc::{IpcSchema, ARROW_MAGIC, CONTINUATION_MARKER};
+
+use super::common::{read_dictionary, read_record_batch};
+use super::reader::get_serialized_batch;
+use super::schema::fb_to_schema;
+use super::Dictionaries;
+use super::FileMetadata;
+
+/// Async reader for Arrow IPC files
+pub struct FileStream<'a> {
+    stream: BoxStream<'a, Result<Chunk<Arc<dyn Array>>>>,
+    metadata: FileMetadata,
+    schema: Schema,
+}
+
+impl<'a> FileStream<'a> {
+    /// Create a new IPC file reader.
+    ///
+    /// # Examples
+    /// See [`FileSink`](crate::io::ipc::write::file_async::FileSink).
+    pub fn new<R>(reader: R, metadata: FileMetadata, projection: Option<Vec<usize>>) -> Self
+    where
+        R: AsyncRead + AsyncSeek + Unpin + Send + 'a,
+    {
+        let schema = if let Some(projection) = projection.as_ref() {
+            projection.windows(2).for_each(|x| {
+                assert!(
+                    x[0] < x[1],
+                    "IPC projection must be ordered and non-overlapping",
+                )
+            });
+            let fields = projection
+                .iter()
+                .map(|&x| metadata.schema.fields[x].clone())
+                .collect::<Vec<_>>();
+            Schema {
+                fields,
+                metadata: metadata.schema.metadata.clone(),
+            }
+        } else {
+            metadata.schema.clone()
+        };
+
+        let stream = Self::stream(reader, metadata.clone(), projection);
+        Self {
+            stream,
+            metadata,
+            schema,
+        }
+    }
+
+    /// Get the metadata from the IPC file.
+    pub fn metadata(&self) -> &FileMetadata {
+        &self.metadata
+    }
+
+    /// Get the projected schema from the IPC file.
+    pub fn schema(&self) -> &Schema {
+        &self.schema
+    }
+
+    fn stream<R>(
+        mut reader: R,
+        metadata: FileMetadata,
+        projection: Option<Vec<usize>>,
+    ) -> BoxStream<'a, Result<Chunk<Arc<dyn Array>>>>
+    where
+        R: AsyncRead + AsyncSeek + Unpin + Send + 'a,
+    {
+        async_stream::try_stream! {
+            let mut meta_buffer = vec![];
+            let mut block_buffer = vec![];
+            for block in 0..metadata.blocks.len() {
+                let chunk = read_batch(
+                    &mut reader,
+                    &metadata,
+                    projection.as_deref(),
+                    block,
+                    &mut meta_buffer,
+                    &mut block_buffer,
+                ).await?;
+                yield chunk;
+            }
+        }
+        .boxed()
+    }
+}
+
+impl<'a> Stream for FileStream<'a> {
+    type Item = Result<Chunk<Arc<dyn Array>>>;
+
+    fn poll_next(
+        self: std::pin::Pin<&mut Self>,
+        cx: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Option<Self::Item>> {
+        self.get_mut().stream.poll_next_unpin(cx)
+    }
+}
+
+/// Read the metadata from an IPC file.
+pub async fn read_file_metadata_async<R>(mut reader: R) -> Result<FileMetadata>
+where
+    R: AsyncRead + AsyncSeek + Unpin,
+{
+    // Check header
+    let mut magic = [0; 6];
+    reader.read_exact(&mut magic).await?;
+    if magic != ARROW_MAGIC {
+        return Err(ArrowError::OutOfSpec(
+            "file does not contain correct Arrow header".to_string(),
+        ));
+    }
+    // Check footer
+    reader.seek(SeekFrom::End(-6)).await?;
+    reader.read_exact(&mut magic).await?;
+    if magic != ARROW_MAGIC {
+        return Err(ArrowError::OutOfSpec(
+            "file does not contain correct Arrow footer".to_string(),
+        ));
+    }
+    // Get footer size
+    let mut footer_size = [0; 4];
+    reader.seek(SeekFrom::End(-10)).await?;
+    reader.read_exact(&mut footer_size).await?;
+    let footer_size = i32::from_le_bytes(footer_size);
+    // Read footer
+    let mut footer = vec![0; footer_size as usize];
+    reader.seek(SeekFrom::End(-10 - footer_size as i64)).await?;
+    reader.read_exact(&mut footer).await?;
+    let footer = FooterRef::read_as_root(&footer[..])
+        .map_err(|err| ArrowError::OutOfSpec(format!("unable to get root as footer: {:?}", err)))?;
+
+    let blocks = footer.record_batches()?.ok_or_else(|| {
+        ArrowError::OutOfSpec("unable to get record batches from footer".to_string())
+    })?;
+    let schema = footer
+        .schema()?
+        .ok_or_else(|| ArrowError::OutOfSpec("unable to get schema from footer".to_string()))?;
+    let (schema, ipc_schema) = fb_to_schema(schema)?;
+    let dictionary_blocks = footer.dictionaries()?;
+    let dictionaries = if let Some(blocks) = dictionary_blocks {
+        read_dictionaries(reader, &schema.fields[..], &ipc_schema, blocks).await?
+    } else {
+        Default::default()
+    };
+
+    Ok(FileMetadata {
+        schema,
+        ipc_schema,
+        blocks: blocks
+            .iter()
+            .map(|block| Ok(block.try_into()?))
+            .collect::<Result<Vec<_>>>()?,
+        dictionaries,
+    })
+}
+
+async fn read_dictionaries<R>(
+    mut reader: R,
+    fields: &[Field],
+    ipc_schema: &IpcSchema,
+    blocks: Vector<'_, BlockRef<'_>>,
+) -> Result<Dictionaries>
+where
+    R: AsyncRead + AsyncSeek + Unpin,
+{
+    let mut dictionaries = Default::default();
+    let mut data = vec![];
+    let mut buffer = vec![];
+
+    for block in blocks {
+        let offset = block.offset() as u64;
+        read_dictionary_message(&mut reader, offset, &mut data).await?;
+
+        let message = MessageRef::read_as_root(&data).map_err(|err| {
+            ArrowError::OutOfSpec(format!("unable to get root as message: {:?}", err))
+        })?;
+        let header = message
+            .header()?
+            .ok_or_else(|| ArrowError::oos("message must have a header"))?;
+        match header {
+            MessageHeaderRef::DictionaryBatch(batch) => {
+                buffer.clear();
+                buffer.resize(block.body_length() as usize, 0);
+                reader.read_exact(&mut buffer).await?;
+                let mut cursor = std::io::Cursor::new(&mut buffer);
+                read_dictionary(batch, fields, ipc_schema, &mut dictionaries, &mut cursor, 0)?;
+            }
+            other => {
+                return Err(ArrowError::OutOfSpec(format!(
+                    "expected DictionaryBatch in dictionary blocks, found {:?}",
+                    other,
+                )))
+            }
+        }
+    }
+    Ok(dictionaries)
+}
+
+async fn read_dictionary_message<R>(mut reader: R, offset: u64, data: &mut Vec<u8>) -> Result<()>
+where
+    R: AsyncRead + AsyncSeek + Unpin,
+{
+    let mut message_size = [0; 4];
+    reader.seek(SeekFrom::Start(offset)).await?;
+    reader.read_exact(&mut message_size).await?;
+    if message_size == CONTINUATION_MARKER {
+        reader.read_exact(&mut message_size).await?;
+    }
+    let footer_size = i32::from_le_bytes(message_size);
+    data.clear();
+    data.resize(footer_size as usize, 0);
+    reader.read_exact(data).await?;
+
+    Ok(())
+}
+
+async fn read_batch<R>(
+    mut reader: R,
+    metadata: &FileMetadata,
+    projection: Option<&[usize]>,
+    block: usize,
+    meta_buffer: &mut Vec<u8>,
+    block_buffer: &mut Vec<u8>,
+) -> Result<Chunk<Arc<dyn Array>>>
+where
+    R: AsyncRead + AsyncSeek + Unpin,
+{
+    let block = metadata.blocks[block];
+    reader.seek(SeekFrom::Start(block.offset as u64)).await?;
+    let mut meta_buf = [0; 4];
+    reader.read_exact(&mut meta_buf).await?;
+    if meta_buf == CONTINUATION_MARKER {
+        reader.read_exact(&mut meta_buf).await?;
+    }
+    let meta_len = i32::from_le_bytes(meta_buf) as usize;
+    meta_buffer.clear();
+    meta_buffer.resize(meta_len, 0);
+    reader.read_exact(meta_buffer).await?;
+
+    let message = MessageRef::read_as_root(&meta_buffer[..])
+        .map_err(|err| ArrowError::oos(format!("unable to parse message: {:?}", err)))?;
+    let batch = get_serialized_batch(&message)?;
+    block_buffer.clear();
+    block_buffer.resize(message.body_length()? as usize, 0);
+    reader.read_exact(block_buffer).await?;
+    let mut cursor = std::io::Cursor::new(block_buffer);
+    let chunk = read_record_batch(
+        batch,
+        &metadata.schema.fields,
+        &metadata.ipc_schema,
+        projection,
+        &metadata.dictionaries,
+        message.version()?,
+        &mut cursor,
+        0,
+    )?;
+    Ok(chunk)
+}

src/io/ipc/read/mod.rs

@@ -20,6 +20,10 @@ mod stream;
 #[cfg_attr(docsrs, doc(cfg(feature = "io_ipc_read_async")))]
 pub mod stream_async;
 
+#[cfg(feature = "io_ipc_read_async")]
+#[cfg_attr(docsrs, doc(cfg(feature = "io_ipc_read_async")))]
+pub mod file_async;
+
 pub use common::{read_dictionary, read_record_batch};
 pub use reader::{read_file_metadata, FileMetadata, FileReader};
 pub use schema::deserialize_schema;

src/io/ipc/read/reader.rs

@@ -26,10 +26,10 @@ pub struct FileMetadata {
     /// The blocks in the file
     ///
     /// A block indicates the regions in the file to read to get data
-    blocks: Vec<arrow_format::ipc::Block>,
+    pub(super) blocks: Vec<arrow_format::ipc::Block>,
 
     /// Dictionaries associated to each dict_id
-    dictionaries: Dictionaries,
+    pub(super) dictionaries: Dictionaries,
 }
 
 /// Arrow File reader
@@ -166,7 +166,7 @@ pub fn read_file_metadata<R: Read + Seek>(reader: &mut R) -> Result<FileMetadata
     })
 }
 
-fn get_serialized_batch<'a>(
+pub(super) fn get_serialized_batch<'a>(
     message: &'a arrow_format::ipc::MessageRef,
 ) -> Result<arrow_format::ipc::RecordBatchRef<'a>> {
     let header = message.header()?.ok_or_else(|| {

src/io/ipc/write/common.rs

@@ -1,3 +1,4 @@
+use std::borrow::{Borrow, Cow};
 use std::sync::Arc;
 
 use arrow_format::ipc::planus::Builder;
@@ -379,3 +380,55 @@ pub struct EncodedData {
 pub(crate) fn pad_to_8(len: usize) -> usize {
     (((len + 7) & !7) - len) as usize
 }
+
+/// An array [`Chunk`] with optional accompanying IPC fields.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Record<'a> {
+    columns: Cow<'a, Chunk<Arc<dyn Array>>>,
+    fields: Option<Cow<'a, [IpcField]>>,
+}
+
+impl<'a> Record<'a> {
+    /// Get the IPC fields for this record.
+    pub fn fields(&self) -> Option<&[IpcField]> {
+        self.fields.as_deref()
+    }
+
+    /// Get the Arrow columns in this record.
+    pub fn columns(&self) -> &Chunk<Arc<dyn Array>> {
+        self.columns.borrow()
+    }
+}
+
+impl From<Chunk<Arc<dyn Array>>> for Record<'static> {
+    fn from(columns: Chunk<Arc<dyn Array>>) -> Self {
+        Self {
+            columns: Cow::Owned(columns),
+            fields: None,
+        }
+    }
+}
+
+impl<'a, F> From<(Chunk<Arc<dyn Array>>, Option<F>)> for Record<'a>
+where
+    F: Into<Cow<'a, [IpcField]>>,
+{
+    fn from((columns, fields): (Chunk<Arc<dyn Array>>, Option<F>)) -> Self {
+        Self {
+            columns: Cow::Owned(columns),
+            fields: fields.map(|f| f.into()),
+        }
+    }
+}
+
+impl<'a, F> From<(&'a Chunk<Arc<dyn Array>>, Option<F>)> for Record<'a>
+where
+    F: Into<Cow<'a, [IpcField]>>,
+{
+    fn from((columns, fields): (&'a Chunk<Arc<dyn Array>>, Option<F>)) -> Self {
+        Self {
+            columns: Cow::Borrowed(columns),
+            fields: fields.map(|f| f.into()),
+        }
+    }
+}