feat(c++): add LRU chunk cache to Arrow chunk readers to avoid redundandt file IO#861
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feat(c++): add LRU chunk cache to Arrow chunk readers to avoid redundandt file IO#861SYaoJun wants to merge 1 commit intoapache:mainfrom
SYaoJun wants to merge 1 commit intoapache:mainfrom
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #861 +/- ##
============================================
+ Coverage 80.60% 80.73% +0.13%
Complexity 615 615
============================================
Files 94 95 +1
Lines 10707 10792 +85
Branches 1055 1059 +4
============================================
+ Hits 8630 8713 +83
- Misses 1837 1839 +2
Partials 240 240
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before benchmark releaseRun ./graph_info_benchmark
2026-02-26T17:27:12+00:00
Running ./graph_info_benchmark
Run on (4 X 3493.21 MHz CPU s)
CPU Caches:
L1 Data 48 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 1280 KiB (x2)
L3 Unified 49152 KiB (x1)
Load Average: 3.38, 2.01, 0.90
----------------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------------
BenchmarkFixture/InitialGraphInfo 202838 ns 202816 ns 3188
2026-02-26T17:27:13+00:00
Running ./arrow_chunk_reader_benchmark
Run on (4 X 3490.97 MHz CPU s)
CPU Caches:
L1 Data 48 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 1280 KiB (x2)
L3 Unified 49152 KiB (x1)
Load Average: 3.38, 2.01, 0.90
-----------------------------------------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------------------------------------------------------------------------
BenchmarkFixture/CreateVertexPropertyArrowChunkReader 6966 ns 6965 ns 100206
BenchmarkFixture/CreateAdjListArrowChunkReader 3578 ns 3577 ns 196996
BenchmarkFixture/CreateAdjListOffsetArrowChunkReader 3551 ns 3550 ns 197172
BenchmarkFixture/AdjListPropertyArrowChunkReaderReadChunk 325547 ns 166224 ns 3893
BenchmarkFixture/AdjListArrowChunkReaderReadChunk 271021 ns 152848 ns 4235
BenchmarkFixture/AdjListOffsetArrowChunkReaderReadChunk 228655 ns 136690 ns 5239
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_AllColumns_V1 357058 ns 189591 ns 3335
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_TwoColumns_V1 361736 ns 201011 ns 3760
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_OneColumns_V1 308693 ns 179371 ns 4042
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_AllColumns_V2 152241 ns 133497 ns 5182
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_TwoColumns_V2 125877 ns 108899 ns 6275
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_OneColumns_V2 97200 ns 82066 ns 8745
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_AllColumns_V1 1234745 ns 396302 ns 1797
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_TwoColumns_V1 821340 ns 301181 ns 2272
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_OneColumns_V1 438876 ns 191486 ns 3756
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_AllColumns_V2 805788 ns 775914 ns 890
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_TwoColumns_V2 502274 ns 462362 ns 1506
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_OneColumns_V2 218477 ns 188513 ns 3677
2026-02-26T17:27:40+00:00
Running ./label_filter_benchmark
Run on (4 X 2820.27 MHz CPU s)
CPU Caches:
L1 Data 48 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 1280 KiB (x2)
L3 Unified 49152 KiB (x1)
Load Average: 2.52, 1.93, 0.91
--------------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------------------------------------
BenchmarkFixture/SingleLabelFilter/iterations:10 111665 ns 111611 ns 10
BenchmarkFixture/SingleLabelFilterbyAcero/iterations:10 1237938 ns 658114 ns 10
BenchmarkFixture/MultiLabelFilter/iterations:10 92731 ns 92712 ns 10
BenchmarkFixture/MultiLabelFilterbyAcero/iterations:10 719147 ns 465075 ns 10
BenchmarkFixture/LabelFilterFromSet/iterations:10 49065 ns 48985 ns 10after benchmark releaseRun ./graph_info_benchmark
2026-02-27T00:34:22+00:00
Running ./graph_info_benchmark
Run on (4 X 3243.65 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 512 KiB (x2)
L3 Unified 32768 KiB (x1)
Load Average: 3.64, 2.29, 1.06
----------------------------------------------------------------------------
Benchmark Time CPU Iterations
----------------------------------------------------------------------------
BenchmarkFixture/InitialGraphInfo 231562 ns 231549 ns 2534
2026-02-27T00:34:23+00:00
Running ./arrow_chunk_reader_benchmark
Run on (4 X 3241.99 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 512 KiB (x2)
L3 Unified 32768 KiB (x1)
Load Average: 3.64, 2.29, 1.06
-----------------------------------------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
-----------------------------------------------------------------------------------------------------------------------------
BenchmarkFixture/CreateVertexPropertyArrowChunkReader 13837 ns 13836 ns 50724
BenchmarkFixture/CreateAdjListArrowChunkReader 7077 ns 7076 ns 98705
BenchmarkFixture/CreateAdjListOffsetArrowChunkReader 7103 ns 7103 ns 98224
BenchmarkFixture/AdjListPropertyArrowChunkReaderReadChunk 256 ns 255 ns 2743767
BenchmarkFixture/AdjListArrowChunkReaderReadChunk 448 ns 448 ns 1645296
BenchmarkFixture/AdjListOffsetArrowChunkReaderReadChunk 248 ns 248 ns 2853157
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_AllColumns_V1 900 ns 899 ns 788047
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_TwoColumns_V1 617 ns 617 ns 1135186
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_OneColumns_V1 434 ns 434 ns 1567110
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_AllColumns_V2 868 ns 868 ns 789657
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_TwoColumns_V2 600 ns 600 ns 1149521
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_firstGraph_OneColumns_V2 418 ns 418 ns 1691556
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_AllColumns_V1 892 ns 890 ns 802783
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_TwoColumns_V1 600 ns 600 ns 1160415
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_OneColumns_V1 430 ns 430 ns 1683496
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_AllColumns_V2 819 ns 819 ns 845382
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_TwoColumns_V2 588 ns 588 ns 1166540
BenchmarkFixture/VertexPropertyArrowChunkReaderReadChunk_secondGraph_OneColumns_V2 420 ns 420 ns 1695935
2026-02-27T00:34:39+00:00
Running ./label_filter_benchmark
Run on (4 X 3263.15 MHz CPU s)
CPU Caches:
L1 Data 32 KiB (x2)
L1 Instruction 32 KiB (x2)
L2 Unified 512 KiB (x2)
L3 Unified 32768 KiB (x1)
Load Average: 2.89, 2.21, 1.05
--------------------------------------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------------------------------------
BenchmarkFixture/SingleLabelFilter/iterations:10 148347 ns 148227 ns 10
BenchmarkFixture/SingleLabelFilterbyAcero/iterations:10 1292426 ns 766637 ns 10
BenchmarkFixture/MultiLabelFilter/iterations:10 109273 ns 109286 ns 10
BenchmarkFixture/MultiLabelFilterbyAcero/iterations:10 818002 ns 539672 ns 10
BenchmarkFixture/LabelFilterFromSet/iterations:10 65665 ns 65433 ns 10summaryPerformance Improvements
Minor Performance Changes
Performance Regressions
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@Sober7135 @yangxk1 I have implemented a basic version of the LRU Cache and summarized the benchmark comparison results in the comments above. Do you have any suggestions or feedback on the code implementation? |
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Pull request overview
Adds an in-memory LRU cache layer to C++ Arrow chunk readers to reduce redundant Parquet reads during seek/backtracking workloads (issue #860), plus introduces a generic LRUCache utility and unit tests.
Changes:
- Introduce
graphar::LRUCache(andPairHash) with Catch2 unit tests. - Wire chunk-level caching into all four Arrow chunk reader implementations to reuse previously loaded
arrow::Tables. - Register the new cache unit test in the C++ CMake test suite.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
cpp/src/graphar/lru_cache.h |
New generic LRU cache + pair hash utility used by chunk readers. |
cpp/src/graphar/arrow/chunk_reader.h |
Adds per-reader cache members for chunk tables. |
cpp/src/graphar/arrow/chunk_reader.cc |
Uses the cache on seek/next_chunk and populates it after reading tables. |
cpp/test/test_lru_cache.cc |
New unit tests covering LRU cache behavior (eviction, update, edge cases). |
cpp/CMakeLists.txt |
Adds test_lru_cache to the test suite. |
Comments suppressed due to low confidence (2)
cpp/src/graphar/arrow/chunk_reader.h:394
- New
chunk_cache_state is introduced, butAdjListArrowChunkReaderdefines a copy assignment operator. Inchunk_reader.cc,operator=currently does not clear or copychunk_cache_, so an instance can retain stale cached tables after assignment (potentially returning data from the previous reader configuration). Please update the assignment operator to reset the cache (and consider whether copy-ctor/assignment should copy or clear cached entries consistently).
std::shared_ptr<arrow::Table> chunk_table_;
LRUCache<std::pair<IdType, IdType>, std::shared_ptr<arrow::Table>, PairHash>
chunk_cache_{4};
IdType vertex_chunk_num_, chunk_num_;
std::string base_dir_;
std::shared_ptr<FileSystem> fs_;
};
cpp/src/graphar/arrow/chunk_reader.h:647
- New
chunk_cache_state is introduced, butAdjListPropertyArrowChunkReaderdefines a copy assignment operator. Inchunk_reader.cc,operator=currently does not clear or copychunk_cache_, so an instance can retain stale cached tables after assignment. Please update the assignment operator to reset the cache (and ensure copy semantics are consistent across ctor/assignment).
std::shared_ptr<arrow::Schema> schema_;
std::shared_ptr<arrow::Table> chunk_table_;
LRUCache<std::pair<IdType, IdType>, std::shared_ptr<arrow::Table>, PairHash>
chunk_cache_{4};
util::FilterOptions filter_options_;
IdType vertex_chunk_num_, chunk_num_;
std::string base_dir_;
std::shared_ptr<FileSystem> fs_;
};
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cpp/src/graphar/lru_cache.h
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| auto h1 = std::hash<T1>{}(p.first); | ||
| auto h2 = std::hash<T2>{}(p.second); | ||
| return h1 ^ (h2 << 32); |
There was a problem hiding this comment.
PairHash combines hashes via h1 ^ (h2 << 32). Shifting by 32 is undefined behavior when size_t is 32-bit, and even on 64-bit this is a weak combiner (high collision risk). Please switch to a portable hash-combine that doesn't assume size_t width (e.g., h1 ^ (h2 + 0x9e3779b97f4a7c15ULL + (h1<<6) + (h1>>2)) or an equivalent width-agnostic approach).
Suggested change
| auto h1 = std::hash<T1>{}(p.first); | |
| auto h2 = std::hash<T2>{}(p.second); | |
| return h1 ^ (h2 << 32); | |
| size_t h1 = std::hash<T1>{}(p.first); | |
| size_t h2 = std::hash<T2>{}(p.second); | |
| // Width-agnostic hash combine (inspired by boost::hash_combine) | |
| constexpr size_t kMul = | |
| static_cast<size_t>(0x9e3779b97f4a7c15ULL); | |
| h1 ^= h2 + kMul + (h1 << 6) + (h1 >> 2); | |
| return h1; |
yangxk1
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Mar 2, 2026
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Looking forward to a benchmark
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| void VertexPropertyArrowChunkReader::Filter(util::Filter filter) { | ||
| filter_options_.filter = filter; | ||
| chunk_table_ = nullptr; |
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Should it be initialized in this xxxFilter function?
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Yes, After filter the cache is outdated.
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| void VertexPropertyArrowChunkReader::Select(util::ColumnNames column_names) { | ||
| filter_options_.columns = column_names; | ||
| chunk_table_ = nullptr; |
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Should it be initialized in this xxxSelect function?
cpp/src/graphar/arrow/chunk_reader.h
Outdated
| IdType vertex_num_; | ||
| std::shared_ptr<arrow::Schema> schema_; | ||
| std::shared_ptr<arrow::Table> chunk_table_; | ||
| LRUCache<IdType, std::shared_ptr<arrow::Table>> chunk_cache_{4}; |
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chunk_cache size can judge based on memory or let the user control it will be better?
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chunk_cache size can judge based on memory or let the user control it will be better?
Actually, I don't know which place is suitable for keep this parameters(size). Do you have any suggestions?
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Putting it in the options and having a default value is a good temporary solution. Maybe we can open a new issue to track it until we can come up with a solution that balances memory, user experience, and efficiency.
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Added LRU CacheSummaryAfter adding the cache, the initialization and creation times have increased. Since filtering and selection operations affect the cache, I currently invalidate all caches aggressively. This has caused performance regressions in filter operations. Performance Improvements
Minor Performance Changes
Performance Regressions
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issue: #860
Reason for this PR
What changes are included in this PR?
Are these changes tested?
Are there any user-facing changes?