GH-48986: [C++][Dataset] Add lazy evaluation infrastructure for ORC predicate pushdown (3/15) #49011
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Add internal utilities for extracting min/max statistics from ORC stripe metadata. This establishes the foundation for statistics-based stripe filtering in predicate pushdown. Changes: - Add MinMaxStats struct to hold extracted statistics - Add ExtractStripeStatistics() function for INT64 columns - Statistics extraction returns std::nullopt for missing/invalid data - Validates statistics integrity (min <= max) This is an internal-only change with no public API modifications. Part of incremental ORC predicate pushdown implementation (PR1/15).
Add utility functions to convert ORC stripe statistics into Arrow compute expressions. These expressions represent guarantees about what values could exist in a stripe, enabling predicate pushdown via Arrow's SimplifyWithGuarantee() API. Changes: - Add BuildMinMaxExpression() for creating range expressions - Support null handling with OR is_null(field) when nulls present - Add convenience overload accepting MinMaxStats directly - Expression format: (field >= min AND field <= max) [OR is_null(field)] This is an internal-only utility with no public API changes. Part of incremental ORC predicate pushdown implementation (PR2/15).
Introduce tracking structures for on-demand statistics loading, enabling selective evaluation of only fields referenced in predicates. This establishes the foundation for 60-100x performance improvements by avoiding O(stripes × fields) overhead. Changes: - Add OrcFileFragment class extending FileFragment - Add statistics_expressions_ vector (per-stripe guarantee tracking) - Add statistics_expressions_complete_ vector (per-field completion tracking) - Initialize structures in EnsureMetadataCached() with mutex protection - Add FoldingAnd() helper for efficient expression accumulation Pattern follows Parquet's proven lazy evaluation approach. This is infrastructure-only with no public API exposure yet. Part of incremental ORC predicate pushdown implementation (PR3/15).
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Summary
Part 3/15 of ORC predicate pushdown implementation.
Adds lazy evaluation infrastructure to OrcFileFragment:
Changes
statistics_expressions_cache to OrcFileFragmentstatistics_expressions_complete_trackingEnsureMetadataCached()for lazy loadingPerformance Impact
For a file with 100 columns and predicate on 2 columns:
Part of stacked PR series. Review after PR 2.