feat(rust): Implement IpcReaderAsync

crates/polars-arrow/src/io/ipc/read/file.rs

@@ -215,7 +215,7 @@ fn deserialize_footer_blocks(
     Ok((footer, blocks))
 }
 
-pub(super) fn deserialize_footer(footer_data: &[u8], size: u64) -> PolarsResult<FileMetadata> {
+pub fn deserialize_footer(footer_data: &[u8], size: u64) -> PolarsResult<FileMetadata> {
     let (footer, blocks) = deserialize_footer_blocks(footer_data)?;
 
     let ipc_schema = footer

crates/polars-arrow/src/io/ipc/read/mod.rs

@@ -30,7 +30,9 @@ pub mod file_async;
 pub(crate) use common::first_dict_field;
 #[cfg(feature = "io_flight")]
 pub(crate) use common::{read_dictionary, read_record_batch};
-pub use file::{read_batch, read_file_dictionaries, read_file_metadata, FileMetadata};
+pub use file::{
+    deserialize_footer, read_batch, read_file_dictionaries, read_file_metadata, FileMetadata,
+};
 use polars_utils::aliases::PlHashMap;
 pub use reader::FileReader;
 pub use schema::deserialize_schema;

crates/polars-io/src/ipc/ipc_file.rs

@@ -90,16 +90,6 @@ fn check_mmap_err(err: PolarsError) -> PolarsResult<()> {
 }
 
 impl<R: MmapBytesReader> IpcReader<R> {
-    #[doc(hidden)]
-    /// A very bad estimate of the number of rows
-    /// This estimation will be entirely off if the file is compressed.
-    /// And will be varying off depending on the data types.
-    pub fn _num_rows(&mut self) -> PolarsResult<usize> {
-        let metadata = self.get_metadata()?;
-        let n_cols = metadata.schema.fields.len();
-        // this magic number 10 is computed from the yellow trip dataset
-        Ok((metadata.size as usize) / n_cols / 10)
-    }
     fn get_metadata(&mut self) -> PolarsResult<&read::FileMetadata> {
         if self.metadata.is_none() {
             let metadata = read::read_file_metadata(&mut self.reader)?;
@@ -164,10 +154,12 @@ impl<R: MmapBytesReader> IpcReader<R> {
         let rechunk = self.rechunk;
         let metadata = read::read_file_metadata(&mut self.reader)?;
 
-        debug_assert!(
-            self.columns.is_none(),
-            "column names must have already been converted into indices",
-        );
+        // NOTE: For some code paths this already happened. See
+        // https://github.com/pola-rs/polars/pull/14984#discussion_r1520125000
+        // where this was introduced.
+        if let Some(columns) = &self.columns {
+            self.projection = Some(columns_to_projection(columns, &metadata.schema)?);
+        }
 
         let schema = if let Some(projection) = &self.projection {
             Arc::new(apply_projection(&metadata.schema, projection))

crates/polars-io/src/ipc/ipc_reader_async.rs

@@ -0,0 +1,260 @@
+use std::ops::Range;
+use std::sync::Arc;
+
+use arrow::io::ipc::read::{get_row_count, FileMetadata, OutOfSpecKind};
+use bytes::Bytes;
+use object_store::path::Path;
+use object_store::{ObjectMeta, ObjectStore};
+use polars_core::datatypes::IDX_DTYPE;
+use polars_core::frame::DataFrame;
+use polars_core::schema::Schema;
+use polars_error::{polars_bail, polars_err, to_compute_err, PolarsResult};
+
+use crate::cloud::{build_object_store, CloudLocation, CloudOptions};
+use crate::pl_async::{
+    tune_with_concurrency_budget, with_concurrency_budget, MAX_BUDGET_PER_REQUEST,
+};
+use crate::predicates::PhysicalIoExpr;
+use crate::prelude::{materialize_projection, IpcReader};
+use crate::RowIndex;
+
+/// Polars specific wrapper for `Arc<dyn ObjectStore>` that limits the number of
+/// concurrent requests for the entire application.
+#[derive(Debug, Clone)]
+pub struct PolarsObjectStore(Arc<dyn ObjectStore>);
+
+impl PolarsObjectStore {
+    pub fn new(store: Arc<dyn ObjectStore>) -> Self {
+        Self(store)
+    }
+
+    pub async fn get(&self, path: &Path) -> PolarsResult<Bytes> {
+        tune_with_concurrency_budget(1, || async {
+            self.0
+                .get(path)
+                .await
+                .map_err(to_compute_err)?
+                .bytes()
+                .await
+                .map_err(to_compute_err)
+        })
+        .await
+    }
+
+    pub async fn get_range(&self, path: &Path, range: Range<usize>) -> PolarsResult<Bytes> {
+        tune_with_concurrency_budget(1, || self.0.get_range(path, range))
+            .await
+            .map_err(to_compute_err)
+    }
+
+    pub async fn get_ranges(
+        &self,
+        path: &Path,
+        ranges: &[Range<usize>],
+    ) -> PolarsResult<Vec<Bytes>> {
+        tune_with_concurrency_budget(
+            (ranges.len() as u32).clamp(0, MAX_BUDGET_PER_REQUEST as u32),
+            || self.0.get_ranges(path, ranges),
+        )
+        .await
+        .map_err(to_compute_err)
+    }
+
+    /// Fetch the metadata of the parquet file, do not memoize it.
+    pub async fn head(&self, path: &Path) -> PolarsResult<ObjectMeta> {
+        with_concurrency_budget(1, || self.0.head(path))
+            .await
+            .map_err(to_compute_err)
+    }
+}
+
+/// An Arrow IPC reader implemented on top of PolarsObjectStore.
+pub struct IpcReaderAsync {
+    store: PolarsObjectStore,
+    path: Path,
+}
+
+#[derive(Default, Clone)]
+pub struct IpcReadOptions {
+    // Names of the columns to include in the output.
+    projection: Option<Vec<String>>,
+
+    // The maximum number of rows to include in the output.
+    row_limit: Option<usize>,
+
+    // Include a column with the row number under the provided name  starting at the provided index.
+    row_index: Option<RowIndex>,
+
+    // Only include rows that pass this predicate.
+    predicate: Option<Arc<dyn PhysicalIoExpr>>,
+}
+
+impl IpcReadOptions {
+    pub fn with_projection(mut self, indices: impl Into<Option<Vec<String>>>) -> Self {
+        self.projection = indices.into();
+        self
+    }
+
+    pub fn with_row_limit(mut self, row_limit: impl Into<Option<usize>>) -> Self {
+        self.row_limit = row_limit.into();
+        self
+    }
+
+    pub fn with_row_index(mut self, row_index: impl Into<Option<RowIndex>>) -> Self {
+        self.row_index = row_index.into();
+        self
+    }
+
+    pub fn with_predicate(mut self, predicate: impl Into<Option<Arc<dyn PhysicalIoExpr>>>) -> Self {
+        self.predicate = predicate.into();
+        self
+    }
+}
+
+impl IpcReaderAsync {
+    pub async fn from_uri(
+        uri: &str,
+        cloud_options: Option<&CloudOptions>,
+    ) -> PolarsResult<IpcReaderAsync> {
+        let (
+            CloudLocation {
+                prefix, expansion, ..
+            },
+            store,
+        ) = build_object_store(uri, cloud_options).await?;
+
+        let path = {
+            // Any wildcards should already have been resolved here. Without this assertion they would
+            // be ignored.
+            debug_assert!(expansion.is_none(), "path should not contain wildcards");
+            Path::from_url_path(prefix).map_err(to_compute_err)?
+        };
+
+        Ok(Self {
+            store: PolarsObjectStore::new(store),
+            path,
+        })
+    }
+
+    async fn object_metadata(&self) -> PolarsResult<ObjectMeta> {
+        self.store.head(&self.path).await
+    }
+
+    async fn file_size(&self) -> PolarsResult<usize> {
+        Ok(self.object_metadata().await?.size)
+    }
+
+    pub async fn metadata(&self) -> PolarsResult<FileMetadata> {
+        let file_size = self.file_size().await?;
+
+        // TODO: Do a larger request and hope that the entire footer is contained within it to save one round-trip.
+        let footer_metadata =
+            self.store
+                .get_range(
+                    &self.path,
+                    file_size.checked_sub(FOOTER_METADATA_SIZE).ok_or_else(|| {
+                        to_compute_err("ipc file size is smaller than the minimum")
+                    })?..file_size,
+                )
+                .await?;
+
+        let footer_size = deserialize_footer_metadata(
+            footer_metadata
+                .as_ref()
+                .try_into()
+                .map_err(to_compute_err)?,
+        )?;
+
+        let footer = self
+            .store
+            .get_range(
+                &self.path,
+                file_size
+                    .checked_sub(FOOTER_METADATA_SIZE + footer_size)
+                    .ok_or_else(|| {
+                        to_compute_err("invalid ipc footer metadata: footer size too large")
+                    })?..file_size,
+            )
+            .await?;
+
+        arrow::io::ipc::read::deserialize_footer(
+            footer.as_ref(),
+            footer_size.try_into().map_err(to_compute_err)?,
+        )
+    }
+
+    pub async fn data(
+        &self,
+        metadata: Option<&FileMetadata>,
+        options: IpcReadOptions,
+        verbose: bool,
+    ) -> PolarsResult<DataFrame> {
+        // TODO: Only download what is needed rather than the entire file by
+        // making use of the projection, row limit, predicate and such.
+        let bytes = self.store.get(&self.path).await?;
+
+        let projection = match options.projection.as_deref() {
+            Some(projection) => {
+                fn prepare_schema(mut schema: Schema, row_index: Option<&RowIndex>) -> Schema {
+                    if let Some(rc) = row_index {
+                        let _ = schema.insert_at_index(0, rc.name.as_str().into(), IDX_DTYPE);
+                    }
+                    schema
+                }
+
+                // Retrieve the metadata for the schema so we can map column names to indices.
+                let fetched_metadata;
+                let metadata = if let Some(metadata) = metadata {
+                    metadata
+                } else {
+                    // This branch is  happens when _metadata is None, which can happen if we Deserialize the execution plan.
+                    fetched_metadata = self.metadata().await?;
+                    &fetched_metadata
+                };
+
+                let schema = prepare_schema((&metadata.schema).into(), options.row_index.as_ref());
+
+                let hive_partitions = None;
+
+                materialize_projection(
+                    Some(projection),
+                    &schema,
+                    hive_partitions,
+                    options.row_index.is_some(),
+                )
+            },
+            None => None,
+        };
+
+        let reader =
+            <IpcReader<_> as crate::SerReader<_>>::new(std::io::Cursor::new(bytes.as_ref()))
+                .with_row_index(options.row_index)
+                .with_n_rows(options.row_limit)
+                .with_projection(projection);
+        reader.finish_with_scan_ops(options.predicate, verbose)
+    }
+
+    pub async fn count_rows(&self, _metadata: Option<&FileMetadata>) -> PolarsResult<i64> {
+        // TODO: Only download what is needed rather than the entire file by
+        // making use of the projection, row limit, predicate and such.
+        let bytes = self.store.get(&self.path).await?;
+        get_row_count(&mut std::io::Cursor::new(bytes.as_ref()))
+    }
+}
+
+const FOOTER_METADATA_SIZE: usize = 10;
+
+// TODO: Move to polars-arrow and deduplicate parsing of footer metadata in
+// sync and async readers.
+fn deserialize_footer_metadata(bytes: [u8; FOOTER_METADATA_SIZE]) -> PolarsResult<usize> {
+    let footer_size: usize =
+        i32::from_le_bytes(bytes[0..4].try_into().unwrap_or_else(|_| unreachable!()))
+            .try_into()
+            .map_err(|_| polars_err!(oos = OutOfSpecKind::NegativeFooterLength))?;
+
+    if &bytes[4..] != b"ARROW1" {
+        polars_bail!(oos = OutOfSpecKind::InvalidFooter);
+    }
+
+    Ok(footer_size)
+}

crates/polars-io/src/ipc/mod.rs

@@ -16,3 +16,8 @@ pub use ipc_file::IpcReader;
 #[cfg(feature = "ipc_streaming")]
 pub use ipc_stream::*;
 pub use write::{BatchedWriter, IpcCompression, IpcWriter, IpcWriterOption};
+
+#[cfg(feature = "cloud")]
+mod ipc_reader_async;
+#[cfg(feature = "cloud")]
+pub use ipc_reader_async::*;