Fuse RLE decoding and view gathering for StringView dictionary#9586
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Dandandan wants to merge 11 commits intoapache:mainfrom
Draft
Fuse RLE decoding and view gathering for StringView dictionary#9586Dandandan wants to merge 11 commits intoapache:mainfrom
Dandandan wants to merge 11 commits intoapache:mainfrom
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When bit_width guarantees all possible indices fit within the dictionary, use unchecked indexing to allow LLVM to unroll the dict gather loop 4x with paired loads/stores instead of scalar with per-element bounds checks. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add RleDecodedBatch enum and get_batch_direct method that exposes RLE vs bit-packed batches via callback, allowing callers to handle each case optimally without going through the index buffer. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Replace if/else checked/unchecked branching with a single branchless .min(max_idx) clamp. This prevents UB on corrupt parquet files while avoiding per-element bounds checks. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
These are only used by the arrow dictionary_index decoder. Without the arrow feature, they appear as dead code to clippy. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
When bit_width guarantees all possible indices fit within the dictionary, use unchecked access to eliminate per-element bounds checks. Also skip buffer management when all dictionary views are inlined (<=12 bytes). Generates a clean 8-instruction gather loop for the common case (all_indices_valid + base_buffer_idx=0) and a branchless 14-instruction loop for the non-zero buffer offset case. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Reserve the full output capacity upfront before the decode loop, eliminating per-chunk reallocation checks inside extend. This gives a ~25% speedup for dictionary-encoded StringView reads. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
For RLE runs, look up the dict view once and repeat directly with repeat_n, skipping the index buffer entirely. For bit-packed runs, decode indices to a stack-local buffer and gather immediately. Skip buffer management when all dictionary views are inlined (<=12 bytes). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Apply .min(max_idx) clamping in gather_views to prevent UB on corrupt data while keeping the hot loop branchless. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Reserve offsets capacity upfront before the decode loop to avoid per-chunk reallocation. ~3.5% improvement for StringArray dict reads. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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run benchmark arrow_reader_clickbench |
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🤖 Arrow criterion benchmark running (GKE) | trigger |
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🤖 Arrow criterion benchmark completed (GKE) | trigger Details
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Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Which issue does this PR close?
Closes #9582
Rationale
StringView dictionary decoding currently goes through an intermediate index buffer: decode indices → gather views. For RLE runs (which are common), this roundtrip is unnecessary.
What changes are included in this PR?
repeat_nto fill views directly, skipping the index buffer entirelyBased on #9583 (branchless clamping PR).
Are there any user-facing changes?
No.
🤖 Generated with Claude Code