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Aikesheng Open Source Community
Aikesheng Open Source Community
Jan 21, 2025 · Databases

Understanding MySQL EXPLAIN EXTRA Hints: Impossible, No Matching, Recursive, Rematerialize, and Canned N Databases

This article explains the meaning and optimization strategies for various MySQL EXPLAIN EXTRA hints—including Impossible WHERE/HAVING, No matching rows, Recursive queries, Rematerialize, and canned N databases—provides example execution plans, code snippets, and performance comparisons to help developers write more efficient SQL statements.

EXPLAINMySQLOptimizer Switch
0 likes · 10 min read
Understanding MySQL EXPLAIN EXTRA Hints: Impossible, No Matching, Recursive, Rematerialize, and Canned N Databases
Aikesheng Open Source Community
Aikesheng Open Source Community
Sep 10, 2021 · Databases

Understanding MySQL 8.0 Derived Condition Pushdown Optimization and Its Impact on User Variables

The article explains MySQL 8.0.22's new optimizer_switch variable derived_condition_pushdown, shows how enabling it can cause unexpected results with user‑defined variables in outer WHERE clauses, provides test cases, explains the underlying behavior, and offers three practical solutions.

MySQLOptimizer SwitchUser Variables
0 likes · 7 min read
Understanding MySQL 8.0 Derived Condition Pushdown Optimization and Its Impact on User Variables
Aikesheng Open Source Community
Aikesheng Open Source Community
Jun 16, 2020 · Databases

Understanding and Optimizing MySQL Multi-Range Read (MRR)

This article explains MySQL's Multi-Range Read (MRR) optimization, demonstrates its performance impact through experiments, shows how to enable or disable MRR via optimizer_switch, and provides guidance on tuning related parameters such as mrr_cost_based and read_rnd_buffer_size for optimal query execution.

MRRMySQLOptimizer Switch
0 likes · 7 min read
Understanding and Optimizing MySQL Multi-Range Read (MRR)