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62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
#include <Columns/ColumnCompressed.h>
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#pragma GCC diagnostic ignored "-Wold-style-cast"
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#include <lz4.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int CANNOT_COMPRESS;
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extern const int CANNOT_DECOMPRESS;
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}
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std::shared_ptr<Memory<>> ColumnCompressed::compressBuffer(const void * data, size_t data_size, bool always_compress)
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{
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size_t max_dest_size = LZ4_COMPRESSBOUND(data_size);
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if (max_dest_size > std::numeric_limits<int>::max())
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throw Exception(ErrorCodes::CANNOT_COMPRESS, "Cannot compress column of size {}", formatReadableSizeWithBinarySuffix(data_size));
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Memory<> compressed(max_dest_size);
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auto compressed_size = LZ4_compress_default(
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reinterpret_cast<const char *>(data),
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compressed.data(),
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static_cast<int>(data_size),
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static_cast<int>(max_dest_size));
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if (compressed_size <= 0)
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throw Exception(ErrorCodes::CANNOT_COMPRESS, "Cannot compress column");
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/// If compression is inefficient.
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if (!always_compress && static_cast<size_t>(compressed_size) * 2 > data_size)
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return {};
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/// Shrink to fit.
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auto shrank = std::make_shared<Memory<>>(compressed_size);
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memcpy(shrank->data(), compressed.data(), compressed_size);
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return shrank;
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}
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void ColumnCompressed::decompressBuffer(
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const void * compressed_data, void * decompressed_data, size_t compressed_size, size_t decompressed_size)
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{
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auto processed_size = LZ4_decompress_safe(
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reinterpret_cast<const char *>(compressed_data),
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reinterpret_cast<char *>(decompressed_data),
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static_cast<int>(compressed_size),
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static_cast<int>(decompressed_size));
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if (processed_size <= 0)
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throw Exception(ErrorCodes::CANNOT_DECOMPRESS, "Cannot decompress column");
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}
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}
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