Async parquet reader (#111)

Add Sync + Send bounds to parquet crate

Author: tustvold

parquet/Cargo.toml

@@ -23,7 +23,7 @@ description = "Apache Parquet implementation in Rust"
 homepage = "https://github.com/apache/arrow-rs"
 repository = "https://github.com/apache/arrow-rs"
 authors = ["Apache Arrow <dev@arrow.apache.org>"]
-keywords = [ "arrow", "parquet", "hadoop" ]
+keywords = ["arrow", "parquet", "hadoop"]
 readme = "README.md"
 build = "build.rs"
 edition = "2021"
@@ -45,6 +45,8 @@ base64 = { version = "0.13", optional = true }
 clap = { version = "2.33.3", optional = true }
 serde_json = { version = "1.0", features = ["preserve_order"], optional = true }
 rand = "0.8"
+futures = { version = "0.3", optional = true }
+tokio = { version = "1.0", optional = true, default-features = false, features = ["macros", "fs", "rt", "io-util"] }
 
 [dev-dependencies]
 criterion = "0.3"
@@ -63,16 +65,18 @@ cli = ["serde_json", "base64", "clap"]
 test_common = []
 # Experimental, unstable functionality primarily used for testing
 experimental = []
+# Experimental, unstable, async API
+async = ["futures", "tokio"]
 
-[[ bin ]]
+[[bin]]
 name = "parquet-read"
 required-features = ["cli"]
 
-[[ bin ]]
+[[bin]]
 name = "parquet-schema"
 required-features = ["cli"]
 
-[[ bin ]]
+[[bin]]
 name = "parquet-rowcount"
 required-features = ["cli"]
 

parquet/src/arrow/array_reader.rs

@@ -42,7 +42,7 @@ use arrow::datatypes::{
     Float32Type as ArrowFloat32Type, Float64Type as ArrowFloat64Type,
     Int16Type as ArrowInt16Type, Int32Type as ArrowInt32Type,
     Int64Type as ArrowInt64Type, Int8Type as ArrowInt8Type, IntervalUnit, Schema,
-    Time32MillisecondType as ArrowTime32MillisecondType,
+    SchemaRef, Time32MillisecondType as ArrowTime32MillisecondType,
     Time32SecondType as ArrowTime32SecondType,
     Time64MicrosecondType as ArrowTime64MicrosecondType,
     Time64NanosecondType as ArrowTime64NanosecondType, TimeUnit as ArrowTimeUnit,
@@ -91,7 +91,7 @@ pub use byte_array::make_byte_array_reader;
 pub use byte_array_dictionary::make_byte_array_dictionary_reader;
 
 /// Array reader reads parquet data into arrow array.
-pub trait ArrayReader {
+pub trait ArrayReader: Send {
     fn as_any(&self) -> &dyn Any;
 
     /// Returns the arrow type of this array reader.
@@ -117,6 +117,26 @@ pub trait ArrayReader {
     fn get_rep_levels(&self) -> Option<&[i16]>;
 }
 
+/// A collection of row groups
+pub trait RowGroupCollection {
+    /// Get schema of parquet file.
+    fn schema(&self) -> Result<SchemaDescPtr>;
+
+    /// Returns an iterator over the column chunks for particular column
+    fn column_chunks(&self, i: usize) -> Result<Box<dyn PageIterator>>;
+}
+
+impl RowGroupCollection for Arc<dyn FileReader> {
+    fn schema(&self) -> Result<SchemaDescPtr> {
+        Ok(self.metadata().file_metadata().schema_descr_ptr())
+    }
+
+    fn column_chunks(&self, column_index: usize) -> Result<Box<dyn PageIterator>> {
+        let iterator = FilePageIterator::new(column_index, Arc::clone(self))?;
+        Ok(Box::new(iterator))
+    }
+}
+
 /// Uses `record_reader` to read up to `batch_size` records from `pages`
 ///
 /// Returns the number of records read, which can be less than batch_size if
@@ -478,7 +498,7 @@ where
 impl<T, C> ArrayReader for ComplexObjectArrayReader<T, C>
 where
     T: DataType,
-    C: Converter<Vec<Option<T::T>>, ArrayRef> + 'static,
+    C: Converter<Vec<Option<T::T>>, ArrayRef> + Send + 'static,
 {
     fn as_any(&self) -> &dyn Any {
         self
@@ -1311,9 +1331,9 @@ impl ArrayReader for StructArrayReader {
 /// Create array reader from parquet schema, column indices, and parquet file reader.
 pub fn build_array_reader<T>(
     parquet_schema: SchemaDescPtr,
-    arrow_schema: Schema,
+    arrow_schema: SchemaRef,
     column_indices: T,
-    file_reader: Arc<dyn FileReader>,
+    row_groups: Box<dyn RowGroupCollection>,
 ) -> Result<Box<dyn ArrayReader>>
 where
     T: IntoIterator<Item = usize>,
@@ -1351,13 +1371,8 @@ where
         fields: filtered_root_fields,
     };
 
-    ArrayReaderBuilder::new(
-        Arc::new(proj),
-        Arc::new(arrow_schema),
-        Arc::new(leaves),
-        file_reader,
-    )
-    .build_array_reader()
+    ArrayReaderBuilder::new(Arc::new(proj), arrow_schema, Arc::new(leaves), row_groups)
+        .build_array_reader()
 }
 
 /// Used to build array reader.
@@ -1367,7 +1382,7 @@ struct ArrayReaderBuilder {
     // Key: columns that need to be included in final array builder
     // Value: column index in schema
     columns_included: Arc<HashMap<*const Type, usize>>,
-    file_reader: Arc<dyn FileReader>,
+    row_groups: Box<dyn RowGroupCollection>,
 }
 
 /// Used in type visitor.
@@ -1667,13 +1682,13 @@ impl<'a> ArrayReaderBuilder {
         root_schema: TypePtr,
         arrow_schema: Arc<Schema>,
         columns_included: Arc<HashMap<*const Type, usize>>,
-        file_reader: Arc<dyn FileReader>,
+        file_reader: Box<dyn RowGroupCollection>,
     ) -> Self {
         Self {
             root_schema,
             arrow_schema,
             columns_included,
-            file_reader,
+            row_groups: file_reader,
         }
     }
 
@@ -1707,10 +1722,10 @@ impl<'a> ArrayReaderBuilder {
             context.rep_level,
             context.path.clone(),
         ));
-        let page_iterator = Box::new(FilePageIterator::new(
-            self.columns_included[&(cur_type.as_ref() as *const Type)],
-            self.file_reader.clone(),
-        )?);
+
+        let page_iterator = self
+            .row_groups
+            .column_chunks(self.columns_included[&(cur_type.as_ref() as *const Type)])?;
 
         let arrow_type: Option<ArrowType> = self
             .get_arrow_field(&cur_type, context)
@@ -2823,7 +2838,8 @@ mod tests {
     #[test]
     fn test_create_array_reader() {
         let file = get_test_file("nulls.snappy.parquet");
-        let file_reader = Arc::new(SerializedFileReader::new(file).unwrap());
+        let file_reader: Arc<dyn FileReader> =
+            Arc::new(SerializedFileReader::new(file).unwrap());
 
         let file_metadata = file_reader.metadata().file_metadata();
         let arrow_schema = parquet_to_arrow_schema(
@@ -2834,9 +2850,9 @@ mod tests {
 
         let array_reader = build_array_reader(
             file_reader.metadata().file_metadata().schema_descr_ptr(),
-            arrow_schema,
+            Arc::new(arrow_schema),
             vec![0usize].into_iter(),
-            file_reader,
+            Box::new(file_reader),
         )
         .unwrap();
 

parquet/src/arrow/arrow_reader.rs

@@ -144,9 +144,9 @@ impl ArrowReader for ParquetFileArrowReader {
                 .metadata()
                 .file_metadata()
                 .schema_descr_ptr(),
-            self.get_schema()?,
+            Arc::new(self.get_schema()?),
             column_indices,
-            self.file_reader.clone(),
+            Box::new(self.file_reader.clone()),
         )?;
 
         ParquetRecordBatchReader::try_new(batch_size, array_reader)