Mem

-- 1. 确保聚合缓冲区够大（必须） SET SESSION group_concat_max_len = 4294967295; -- 2. 笛卡尔积生成 5000 行（无任何递归深度限制，纯数学乘法） SELECT LENGTH(GROUP_CONCAT(REPEAT('X', 1048576) SEPARATOR '')) AS memory_used_mb FROM ( SELECT 1 FROM (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5) a, (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5) b, (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5) c, (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5) d, (SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5) e, (SELECT 1 UNION ALL SELECT 2) f -- 5^5 * 2 = 6250 行，LIMIT 取 5000 LIMIT 5000 ) t;

如果要 10GB，把 LIMIT 5000 改成 LIMIT 10000；如果要 20GB，改成 LIMIT 20000。