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GH-45092: [C++][Parquet] Add GetReadRanges function to FileReader #45093

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merged 4 commits into from
Jan 5, 2025
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GH-45092: [C++][Parquet] Add GetReadRanges function to FileReader #45093

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b9f1278
GH-45092: [C++][Parquet] Add GetReadRanges function to FileReader
zeroshade Dec 20, 2024
5fdd78c
fix lint and rename var
zeroshade Dec 23, 2024
b5621a4
add third forward slash for doxygen
zeroshade Jan 3, 2025
42002fa
run pre-commit lint
zeroshade Jan 3, 2025
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16 changes: 16 additions & 0 deletions cpp/src/parquet/file_reader.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
#include "arrow/io/caching.h"
#include "arrow/io/file.h"
#include "arrow/io/memory.h"
#include "arrow/io/util_internal.h"
#include "arrow/util/bit_util.h"
#include "arrow/util/checked_cast.h"
#include "arrow/util/future.h"
Expand Down Expand Up @@ -400,6 +401,21 @@ class SerializedFile : public ParquetFileReader::Contents {
PARQUET_THROW_NOT_OK(cached_source_->Cache(ranges));
}

::arrow::Result<std::vector<::arrow::io::ReadRange>> GetReadRanges(
const std::vector<int>& row_groups, const std::vector<int>& column_indices,
int64_t hole_size_limit, int64_t range_size_limit) {
std::vector<::arrow::io::ReadRange> ranges;
for (int row : row_groups) {
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for (int col : column_indices) {
ranges.push_back(
ComputeColumnChunkRange(file_metadata_.get(), source_size_, row, col));
}
}

return ::arrow::io::internal::CoalesceReadRanges(std::move(ranges), hole_size_limit,
range_size_limit);
}

::arrow::Future<> WhenBuffered(const std::vector<int>& row_groups,
const std::vector<int>& column_indices) const {
if (!cached_source_) {
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26 changes: 26 additions & 0 deletions cpp/src/parquet/file_reader.h
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Expand Up @@ -201,6 +201,32 @@ class PARQUET_EXPORT ParquetFileReader {
const ::arrow::io::IOContext& ctx,
const ::arrow::io::CacheOptions& options);

// Retrieve the list of byte ranges that would need to be read to retrieve
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FWIW, use /// for a doxygen comment

// the data for the specified row groups and column indices.
//
// A reader can optionally call this if they wish to handle their own
// caching and management of file reads (or offload them to other readers).
// Unlike PreBuffer, this method will not perform any actual caching or
// reads, instead just using the file metadata to determine the byte ranges
// that would need to be read if you were to consume the entirety of the column
// chunks for the provided columns in the specified row groups.
//
// If row_groups or column_indices are empty, then the result of this will be empty.
//
// hole_size_limit represents the maximum distance, in bytes, between two
// consecutive ranges; beyond this value, ranges will not be combined. The default
// value is 1MB.
//
// range_size_limit is the maximum size in bytes of a combined range; if combining
// two consecutive ranges would produce a range larger than this, they are not combined.
// The default values is 64MB. This *must* be larger than hole_size_limit.
//
// This will not take into account page indexes or any other predicate push down
// benefits that may be available.
::arrow::Result<std::vector<::arrow::io::ReadRange>> GetReadRanges(
const std::vector<int>& row_groups, const std::vector<int>& column_indices,
int64_t hole_size_limit = 1024 * 1024, int64_t range_size_limit = 64 * 1024 * 1024);

/// Wait for the specified row groups and column indices to be pre-buffered.
///
/// After the returned Future completes, reading the specified row
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