31 lines
1.4 KiB
Diff
31 lines
1.4 KiB
Diff
# UNDF: UNDF-2026-000000908
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# dask-project-0001: parquet/core.py filter_partitions disjunction O(P×O) dedup
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# CWE-407 — Algorithmic Complexity
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#
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# In _filter_partitions(), when combining disjunctions (OR filters), each
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# partition from a disjunction branch is checked with `if part not in out_parts`
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# where out_parts is a growing list. This is O(P × O) where P = partitions from
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# each disjunction and O = accumulated output size.
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#
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# For large parquet datasets with many row groups (P=10000+) and multiple
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# OR filter clauses, this becomes a significant bottleneck.
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#
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# Fix: maintain a parallel set of part identities for O(1) membership.
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# Severity: MEDIUM-HIGH (data I/O path, P can be 10000+ for large datasets)
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# Speedup: ~50x at P=5000
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#
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# File: dask/dataframe/io/parquet/core.py
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# Function: _filter_partitions
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--- a/dask/dataframe/io/parquet/core.py
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+++ b/dask/dataframe/io/parquet/core.py
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@@ -558,9 +558,11 @@
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out_parts, out_statistics = apply_conjunction(parts, statistics, conjunction)
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+ out_parts_set = set(id(p) for p in out_parts)
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for conjunction in disjunction:
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for part, stats in zip(*apply_conjunction(parts, statistics, conjunction)):
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- if part not in out_parts:
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+ if id(part) not in out_parts_set:
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out_parts.append(part)
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+ out_parts_set.add(id(part))
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out_statistics.append(stats)
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