README

Planner Notes

• rule: rule-related notes and decisions.
• plan_cache_notes.md: plan cache and binding matching notes.
• redundant_using_join_notes.md: notes for redundant-column handling around JOIN ... USING / NATURAL JOIN.
• window_subquery_notes.md: deferred window rewrite notes for correlated and non-scalar subqueries.
• window_frame_replace_notes.md: notes for window-frame column replacement during projection elimination.