Merge pull request #242 from Altinity/backports/22.8.15/optimization_…

…parquet_reader

Backport upstream ClickHouse#45478

src/Processors/Formats/Impl/ArrowBufferedStreams.cpp

@@ -11,6 +11,7 @@
 #include <IO/copyData.h>
 #include <IO/PeekableReadBuffer.h>
 #include <arrow/buffer.h>
+#include <arrow/util/future.h>
 #include <arrow/io/memory.h>
 #include <arrow/result.h>
 #include <Core/Settings.h>
@@ -95,6 +96,12 @@ arrow::Result<std::shared_ptr<arrow::Buffer>> RandomAccessFileFromSeekableReadBu
     return buffer;
 }
 
+arrow::Future<std::shared_ptr<arrow::Buffer>> RandomAccessFileFromSeekableReadBuffer::ReadAsync(const arrow::io::IOContext &, int64_t position, int64_t nbytes)
+{
+    /// Just a stub to to avoid using internal arrow thread pool
+    return arrow::Future<std::shared_ptr<arrow::Buffer>>::MakeFinished(ReadAt(position, nbytes));
+}
+
 arrow::Status RandomAccessFileFromSeekableReadBuffer::Seek(int64_t position)
 {
     seekable_in.seek(position, SEEK_SET);

src/Processors/Formats/Impl/ArrowBufferedStreams.h

@@ -62,6 +62,11 @@ class RandomAccessFileFromSeekableReadBuffer : public arrow::io::RandomAccessFil
 
     arrow::Result<std::shared_ptr<arrow::Buffer>> Read(int64_t nbytes) override;
 
+    /// Override async reading to avoid using internal arrow thread pool.
+    /// In our code we don't use async reading, so implementation is sync,
+    /// we just call ReadAt and return future with ready value.
+    arrow::Future<std::shared_ptr<arrow::Buffer>> ReadAsync(const arrow::io::IOContext&, int64_t position, int64_t nbytes) override;
+
     arrow::Status Seek(int64_t position) override;
 
 private: