postgres-patterns

PostgreSQL 模式

PostgreSQL 最佳实践快速参考。如需详细指导，请使用 database-reviewer 智能体。

何时激活

• 编写 SQL 查询或迁移时
• 设计数据库模式时
• 排查慢查询时
• 实施行级安全性时
• 设置连接池时

快速参考

索引速查表

查询模式	索引类型	示例
WHERE col = value	B-tree（默认）	CREATE INDEX idx ON t (col)
WHERE col > value	B-tree	CREATE INDEX idx ON t (col)
WHERE a = x AND b > y	复合索引	CREATE INDEX idx ON t (a, b)
WHERE jsonb @> '{}'	GIN	CREATE INDEX idx ON t USING gin (col)
WHERE tsv @@ query	GIN	CREATE INDEX idx ON t USING gin (col)
时间序列范围查询	BRIN	CREATE INDEX idx ON t USING brin (col)

数据类型快速参考

使用场景	正确类型	避免使用
ID	bigint	int，随机 UUID
字符串	text	varchar(255)
时间戳	timestamptz	timestamp
货币	numeric(10,2)	float
标志位	boolean	varchar，int

常见模式

复合索引顺序：

-- Equality columns first, then range columns
CREATE INDEX idx ON orders (status, created_at);
-- Works for: WHERE status = 'pending' AND created_at > '2024-01-01'

覆盖索引：

CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
-- Avoids table lookup for SELECT email, name, created_at

部分索引：

CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
-- Smaller index, only includes active users

RLS 策略（优化版）：

CREATE POLICY policy ON orders
  USING ((SELECT auth.uid()) = user_id);  -- Wrap in SELECT!

UPSERT：

INSERT INTO settings (user_id, key, value)
VALUES (123, 'theme', 'dark')
ON CONFLICT (user_id, key)
DO UPDATE SET value = EXCLUDED.value;

游标分页：

SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
-- O(1) vs OFFSET which is O(n)

队列处理：

UPDATE jobs SET status = 'processing'
WHERE id = (
  SELECT id FROM jobs WHERE status = 'pending'
  ORDER BY created_at LIMIT 1
  FOR UPDATE SKIP LOCKED
) RETURNING *;

反模式检测**

-- Find unindexed foreign keys
SELECT conrelid::regclass, a.attname
FROM pg_constraint c
JOIN pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY(c.conkey)
WHERE c.contype = 'f'
  AND NOT EXISTS (
    SELECT 1 FROM pg_index i
    WHERE i.indrelid = c.conrelid AND a.attnum = ANY(i.indkey)
  );

-- Find slow queries
SELECT query, mean_exec_time, calls
FROM pg_stat_statements
WHERE mean_exec_time > 100
ORDER BY mean_exec_time DESC;

-- Check table bloat
SELECT relname, n_dead_tup, last_vacuum
FROM pg_stat_user_tables
WHERE n_dead_tup > 1000
ORDER BY n_dead_tup DESC;