feat: introduce opendal AsyncReader for parquet integrations (#4972)

integrations/parquet/Cargo.toml

@@ -50,3 +50,7 @@ arrow = { version = "52.0" }
 [[example]]
 name = "async_writer"
 path = "examples/async_writer.rs"
+
+[[example]]
+name = "async_reader"
+path = "examples/async_reader.rs"

integrations/parquet/examples/async_reader.rs

@@ -0,0 +1,57 @@
+use std::sync::Arc;
+
+use arrow::array::{ArrayRef, Int64Array, RecordBatch};
+
+use futures::StreamExt;
+use opendal::{services::S3Config, Operator};
+use parquet::arrow::{AsyncArrowWriter, ParquetRecordBatchStreamBuilder};
+use parquet_opendal::{AsyncReader, AsyncWriter};
+
+#[tokio::main]
+async fn main() {
+    let mut cfg = S3Config::default();
+    cfg.access_key_id = Some("my_access_key".to_string());
+    cfg.secret_access_key = Some("my_secret_key".to_string());
+    cfg.endpoint = Some("my_endpoint".to_string());
+    cfg.region = Some("my_region".to_string());
+    cfg.bucket = "my_bucket".to_string();
+
+    // Create a new operator
+    let operator = Operator::from_config(cfg).unwrap().finish();
+    let path = "/path/to/file.parquet";
+
+    // Create an async writer
+    let writer = AsyncWriter::new(
+        operator
+            .writer_with(path)
+            .chunk(32 * 1024 * 1024)
+            .concurrent(8)
+            .await
+            .unwrap(),
+    );
+
+    let col = Arc::new(Int64Array::from_iter_values([1, 2, 3])) as ArrayRef;
+    let to_write = RecordBatch::try_from_iter([("col", col)]).unwrap();
+    let mut writer = AsyncArrowWriter::try_new(writer, to_write.schema(), None).unwrap();
+    writer.write(&to_write).await.unwrap();
+    writer.close().await.unwrap();
+
+    // gap: Allow the underlying reader to merge small IOs
+    // when the gap between multiple IO ranges is less than the threshold.
+    let reader = operator
+        .reader_with(path)
+        .gap(512 * 1024)
+        .chunk(16 * 1024 * 1024)
+        .concurrent(16)
+        .await
+        .unwrap();
+    let content_len = operator.stat(path).await.unwrap().content_length();
+    let reader = AsyncReader::new(reader, content_len).with_prefetch_footer_size(512 * 1024);
+    let mut stream = ParquetRecordBatchStreamBuilder::new(reader)
+        .await
+        .unwrap()
+        .build()
+        .unwrap();
+    let read = stream.next().await.unwrap().unwrap();
+    assert_eq!(to_write, read);
+}