Optimize Substrait Plan for SQL Pushdown

Rewrite a normal Substrait plan JSON into the compact full-pushdown shape used by the Natural Language to DataStage flow workflow:

Natural language -> Substrait plan -> Optimization -> optimized Substrait plan -> DataStage flow

This skill classifies full SQL pushdown versus partial SQL pushdown, but it only generates optimized output for full pushdown. If full pushdown is not provably safe, stop and return the original plan plus the reason. Do not attempt to split the plan into partial database and DataStage fragments yet.

Inputs

Required:

• A valid Substrait plan JSON object or JSON string.