[JingsongLi]

Purpose

Closes #1284.

DataFusion rejects LATERAL VIEW. A correlated UNNEST subquery is insufficient because the native physical planner cannot execute the projected outer reference.

Brief change log

• Support explode/posexplode and outer variants for arrays/maps with zero-based positions and exact empty/NULL behavior.
• Use a relation-planner extension to plan the parent input and native list/struct UNNEST without correlated physical expressions or collecting the parent.
• Preserve aliases, joins, chained generators, set-operation branches and portable persistent-view SQL; compensate for the pinned parser's optional-alias clause handling.

Tests

• Retain a permanent integration regression that uses comment DDL, binary casts, regex operators, lateral generators, scalar functions and constant CALL arguments together, protecting composition of their shared SQL hooks.

• Regression coverage: Array/Map values, NULL and empty collections, NULL elements, empty parent inputs, map defaults, quoted and explicit aliases, joins/duplicate rows, chained generators, UNION, dictionary collection/value nulls, and default-alias ORDER/LIMIT/OFFSET/QUALIFY boundaries.

• Reproduced the missing behavior on the original main before implementation.

• Passed cargo test --locked -p paimon-datafusion --all-targets -- --test-threads=4 on this independent branch with Rust 1.95.0, TZ=UTC and RUST_MIN_STACK=16777216.

• Passed cargo +1.98.0 clippy --locked --no-deps -p paimon-datafusion --all-targets -- -D warnings, formatting and git diff --check.

• Reviewed repeatedly for SQL semantics, parser/type boundaries and regression quality; fixed the discovered alias, set-operation and default-column parsing cases.

• Integration validation: combined with feat(datafusion): support table and column comment DDL #1287, feat(datafusion): support binary casts and byte widths #1288, feat(datafusion): support RLIKE and REGEXP operators #1289, feat(datafusion): add common scalar compatibility functions #1291, feat(datafusion): evaluate immutable constant CALL arguments #1290 in a temporary checkout; the full DataFusion suite, a regression using all six extensions together, Clippy and formatting passed. These PRs are independently based on main; overlapping parser/registration hooks need normal conflict resolution when merged sequentially.

API and Format

Adds SQLContext SQL capabilities. No storage-format or Rust public API changes.

Documentation

Documented syntax, type/null/error behavior and supported limits in docs/src/sql.md.

[leaves12138]

LGTM