-- 可走索引：前缀匹配
SELECT * FROM users WHERE name LIKE 'wang%';

-- 不可走索引：前置通配
SELECT * FROM users WHERE name LIKE '%wang%';

-- 替代一：MySQL 全文索引
ALTER TABLE articles ADD FULLTEXT INDEX ft_content (content);
SELECT * FROM articles WHERE MATCH(content) AGAINST('mysql' IN BOOLEAN MODE);

-- 替代二：PostgreSQL trigram 索引（需 pg_trgm）
CREATE EXTENSION IF NOT EXISTS pg_trgm;
CREATE INDEX idx_content_trgm ON articles USING GIN (content gin_trgm_ops);
SELECT * FROM articles WHERE content LIKE '%mysql%';