[JingsongLi]

Purpose

A read type that selects only fields inside an ARRAY or MAP must reach the Parquet leaf-column projection. For example, reading only items[].wanted from ARRAY<ROW<wanted, unused>> should avoid decoding unused, including through mixed ROW/ARRAY/MAP nesting.

This also makes formats without nested projection support read complete physical fields and restore the requested shape outside the decoder, while preserving Java Paimon's field-ID and null/anchor semantics.

Brief change log

• Add a format-level nested-projection capability. Parquet opts in; other formats expand nested fields and use outer reconciliation.
• Recursively prune ROW, ARRAY elements, and MAP keys/values, preserving file names, IDs, physical types, defaults, and Java's all-missing-field behavior.
• Build Parquet leaf masks for standard and legacy LIST layouts, MAP keys/values, and shared-shredding MAP value projections.
• Preserve omitted descendants during fallback reconciliation so decoding a complete ROW cannot resurrect a container that logical pruning removed.
• Fix Avro child resolution when the first nested ROW is null. Add a Vortex 0.75 read-side fallback that reconstructs each ROW with its independent validity and selects rows before Arrow export.
• Add mixed-container, null/empty, schema-evolution, duplicate-key, physical-I/O, Java-written LIST fixture, and ORC fallback regressions. Keep Java's complete-value restriction for selected-key MAP projections.

Tests

• cargo fmt --all -- --check: passed.
• Paimon library suite with vortex: 4671 passed, 6 ignored.
• 79 other Paimon integration/example targets passed in batches; the initial aggregate build exceeded local disk capacity.
• Java golden warehouse suites: 82 passed (11 append-table tests and 71 read-table tests).
• cargo clippy --locked --all-targets --workspace --features vortex -- -D warnings -A clippy::nonminimal_bool: passed. Strict Clippy is blocked by four pre-existing warnings in unchanged de_vector_read.rs (two), table_merge_into.rs, and vector_search_common.rs.
• Multiple independent review/fix rounds completed without remaining findings.

Local full-suite builds used CARGO_INCREMENTAL=0 and CARGO_PROFILE_TEST_DEBUG=0 to limit build artifacts.

API and Format

No public API, table option, or on-disk format changes. Nested requests continue to use with_read_type. Readers that cannot prune nested fields keep full decoder types and apply projection outside the format reader.

Documentation

Implementation comments document the format capability, Java-compatible pruning behavior, and Vortex validity fallback. Fixture generators are included alongside the saved test files.

AI assistance

Codex assisted with implementation, regression testing, and review.

[leaves12138]

LGTM