- Implemented GetOrcColumnIndex helper function that:
  - Resolves FieldRef to ORC column index using manifest
  - Uses FieldRef.FindOne() to locate field in schema
  - Traverses manifest tree following field path indices
  - Handles both top-level and nested fields
  - Returns column_index for leaf nodes (primitives with statistics)
  - Returns std::nullopt for containers or not found

- Added necessary includes:
  - <optional> for std::optional return type
  - arrow/compute/api_scalar.h for FieldRef and FieldPath

Implementation details:
- Top-level fields accessed via manifest.schema_fields[index]
- Nested fields traversed via current_field->children[index]
- Validates indices at each level to prevent out-of-bounds
- Only returns column_index if field is leaf (has statistics)
- Containers (struct/list/map) return nullopt

Verified: Manual code review - follows FieldRef resolution pattern

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

- Implemented GetOrcColumnIndex helper function that:
  - Resolves FieldRef to ORC column index using manifest
  - Uses FieldRef.FindOne() to locate field in schema
  - Traverses manifest tree following field path indices
  - Handles both top-level and nested fields
  - Returns column_index for leaf nodes (primitives with statistics)
  - Returns std::nullopt for containers or not found

- Added necessary includes:
  - <optional> for std::optional return type
  - arrow/compute/api_scalar.h for FieldRef and FieldPath

Implementation details:
- Top-level fields accessed via manifest.schema_fields[index]
- Nested fields traversed via current_field->children[index]
- Validates indices at each level to prevent out-of-bounds
- Only returns column_index if field is leaf (has statistics)
- Containers (struct/list/map) return nullopt

Verified: Manual code review - follows FieldRef resolution pattern

Co-authored-by: Claude Sonnet 4.5 <[email protected]>

- Implemented GetOrcColumnIndex helper function that:
  - Resolves FieldRef to ORC column index using manifest
  - Uses FieldRef.FindOne() to locate field in schema
  - Traverses manifest tree following field path indices
  - Handles both top-level and nested fields
  - Returns column_index for leaf nodes (primitives with statistics)
  - Returns std::nullopt for containers or not found

- Added necessary includes:
  - <optional> for std::optional return type
  - arrow/compute/api_scalar.h for FieldRef and FieldPath

Implementation details:
- Top-level fields accessed via manifest.schema_fields[index]
- Nested fields traversed via current_field->children[index]
- Validates indices at each level to prevent out-of-bounds
- Only returns column_index if field is leaf (has statistics)
- Containers (struct/list/map) return nullopt

Verified: Manual code review - follows FieldRef resolution pattern

Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Adds comprehensive task tracking and progress documentation for the
ongoing ORC predicate pushdown implementation project.

## Changes
- task_list.json: Complete 35-task breakdown with dependencies
  - Tasks #0, #0.5, #1, #2 marked as complete (on feature branches)
  - Tasks #3-apache#35 pending implementation
  - Organized by phase: Prerequisites, Core, Metadata, Predicate, Scan, Testing, Future
- claude-progress.txt: Comprehensive project status document
  - Codebase structure and build instructions
  - Work completed on feature branches (not yet merged)
  - Current main branch state
  - Next steps and implementation strategy
  - Parquet mirroring patterns and Allium spec alignment

## Context
This is an initialization session to establish baseline tracking for the
ORC predicate pushdown project. Previous sessions (1-4) completed initial
tasks on feature branches. This consolidates that progress and provides
a clear roadmap for future implementation sessions.

## Related Work
- Allium spec: orc-predicate-pushdown.allium (already on main)
- Feature branches: task-0-statistics-api-v2, task-0.5-stripe-selective-reading,
  task-1-orc-schema-manifest, task-2-build-orc-schema-manifest (not yet merged)

## Next Steps
Future sessions will implement tasks #3+ via individual feature branch PRs.

- Added GetOrcColumnIndex function to resolve FieldRef to ORC column index
- Handles top-level fields via direct lookup
- Handles nested fields via manifest tree traversal
- Returns nullopt if field not found or not a leaf field
- Only leaf fields have statistics and valid column indices
- Added <optional> include for std::optional support

Verified: Code structure follows Parquet pattern

Implemented the GetOrcColumnIndex function that resolves field references
to ORC physical column indices using the schema manifest. This is a critical
component for predicate pushdown to map Arrow field references to ORC columns
for statistics lookup.

Implementation details:
- Added GetOrcColumnIndex() in internal namespace (file_orc.cc)
- Handles top-level field resolution (simple name references)
- Handles nested field resolution (traverses manifest tree)
- Returns std::nullopt for:
  * Fields not found in manifest
  * Container types (struct, list, map) with no single column index
  * Non-name field references (positional, etc.)

Testing:
- Added GetOrcColumnIndex_TopLevelFields test
  * Verifies resolution of simple top-level fields
  * Tests non-existent field returns nullopt
- Added GetOrcColumnIndex_NestedFields test
  * Verifies nested field traversal through struct
  * Tests container field returns nullopt (no single column)
  * Tests invalid nested paths return nullopt

Design follows Parquet's ResolveOneFieldRef pattern adapted for ORC's
manifest structure.

VERIFICATION STATUS: Build/test verification pending due to network
restrictions preventing CMake from downloading dependencies. Previous
session (Task #2) verified all code compiles and tests pass. This
implementation follows established patterns exactly and includes the
necessary <optional> header.

Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Adds comprehensive task tracking and progress documentation for the
ongoing ORC predicate pushdown implementation project.

## Changes
- task_list.json: Complete 35-task breakdown with dependencies
  - Tasks #0, #0.5, #1, #2 marked as complete (on feature branches)
  - Tasks #3-apache#35 pending implementation
  - Organized by phase: Prerequisites, Core, Metadata, Predicate, Scan, Testing, Future
- claude-progress.txt: Comprehensive project status document
  - Codebase structure and build instructions
  - Work completed on feature branches (not yet merged)
  - Current main branch state
  - Next steps and implementation strategy
  - Parquet mirroring patterns and Allium spec alignment

## Context
This is an initialization session to establish baseline tracking for the
ORC predicate pushdown project. Previous sessions (1-4) completed initial
tasks on feature branches. This consolidates that progress and provides
a clear roadmap for future implementation sessions.

## Related Work
- Allium spec: orc-predicate-pushdown.allium (already on main)
- Feature branches: task-0-statistics-api-v2, task-0.5-stripe-selective-reading,
  task-1-orc-schema-manifest, task-2-build-orc-schema-manifest (not yet merged)

## Next Steps
Future sessions will implement tasks #3+ via individual feature branch PRs.

- Added GetOrcColumnIndex function to resolve FieldRef to ORC column index
- Handles top-level fields via direct lookup
- Handles nested fields via manifest tree traversal
- Returns nullopt if field not found or not a leaf field
- Only leaf fields have statistics and valid column indices
- Added <optional> include for std::optional support

Verified: Code structure follows Parquet pattern

Implemented the GetOrcColumnIndex function that resolves field references
to ORC physical column indices using the schema manifest. This is a critical
component for predicate pushdown to map Arrow field references to ORC columns
for statistics lookup.

Implementation details:
- Added GetOrcColumnIndex() in internal namespace (file_orc.cc)
- Handles top-level field resolution (simple name references)
- Handles nested field resolution (traverses manifest tree)
- Returns std::nullopt for:
  * Fields not found in manifest
  * Container types (struct, list, map) with no single column index
  * Non-name field references (positional, etc.)

Testing:
- Added GetOrcColumnIndex_TopLevelFields test
  * Verifies resolution of simple top-level fields
  * Tests non-existent field returns nullopt
- Added GetOrcColumnIndex_NestedFields test
  * Verifies nested field traversal through struct
  * Tests container field returns nullopt (no single column)
  * Tests invalid nested paths return nullopt

Design follows Parquet's ResolveOneFieldRef pattern adapted for ORC's
manifest structure.

VERIFICATION STATUS: Build/test verification pending due to network
restrictions preventing CMake from downloading dependencies. Previous
session (Task #2) verified all code compiles and tests pass. This
implementation follows established patterns exactly and includes the
necessary <optional> header.

Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Added GetORCType() method to ORCFileReader that returns a pointer to the
ORC Type object. This is needed for building schema manifests that map
Arrow schema fields to ORC physical column indices.

The ORC type tree uses depth-first pre-order numbering where column 0 is
the root struct, column 1 is the first top-level field, etc.

Returns const void* to avoid exposing ORC headers in the public Arrow API.
Callers should cast to const orc::Type* to use.

Co-authored-by: Claude Sonnet 4.5 <[email protected]>

Task #3 (Add GetORCType accessor to expose ORC type tree) was completed and merged in PR apache#137.