This article explores the outer join elimination feature in the KingbaseES (KES) query optimizer, a PostgreSQL-compatible database. It explains the specific conditions under which outer joins can be eliminated, such as when the join is guaranteed to produce no null rows, and how this affects the execution plan. The analysis includes practical examples and execution plan comparisons, showing performance improvements. For database engineers working with PostgreSQL or its derivatives, this is a valuable reference for understanding optimizer internals and tuning queries. The content is original and technically rigorous, making it a strong signal for the database community.
A detailed analysis of outer join elimination in KingbaseES, covering trigger conditions and execution plan impacts.