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147 lines
4.1 KiB
Markdown
147 lines
4.1 KiB
Markdown
---
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name: postgres-patterns
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description: PostgreSQL 数据库模式，涵盖查询优化、模式设计、索引和安全性。基于 Supabase 最佳实践。
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---
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# PostgreSQL 模式（Patterns）
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PostgreSQL 最佳实践快速参考。如需详细指导，请使用 `database-reviewer` 智能体（Agent）。
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## 何时激活
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- 编写 SQL 查询或迁移（Migrations）
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- 设计数据库模式（Schemas）
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- 排除慢查询故障
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- 实现行级安全性（Row Level Security, RLS）
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- 设置连接池（Connection Pooling）
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## 快速参考
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### 索引备忘单（Index Cheat Sheet）
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| 查询模式 | 索引类型 | 示例 |
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|--------------|------------|---------|
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| `WHERE col = value` | B-tree（默认） | `CREATE INDEX idx ON t (col)` |
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| `WHERE col > value` | B-tree | `CREATE INDEX idx ON t (col)` |
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| `WHERE a = x AND b > y` | 复合索引（Composite） | `CREATE INDEX idx ON t (a, b)` |
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| `WHERE jsonb @> '{}'` | GIN | `CREATE INDEX idx ON t USING gin (col)` |
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| `WHERE tsv @@ query` | GIN | `CREATE INDEX idx ON t USING gin (col)` |
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| 时序范围（Time-series ranges） | BRIN | `CREATE INDEX idx ON t USING brin (col)` |
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### 数据类型快速参考
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| 用例 | 正确类型 | 避免使用 |
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|----------|-------------|-------|
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| ID | `bigint` | `int`, 随机 UUID |
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| 字符串 | `text` | `varchar(255)` |
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| 时间戳 | `timestamptz` | `timestamp` |
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| 金额 | `numeric(10,2)` | `float` |
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| 标志位（Flags） | `boolean` | `varchar`, `int` |
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### 常用模式
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**复合索引顺序：**
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```sql
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-- 等值列（Equality columns）在前，范围列（Range columns）在后
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CREATE INDEX idx ON orders (status, created_at);
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-- 适用于：WHERE status = 'pending' AND created_at > '2024-01-01'
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```
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**覆盖索引（Covering Index）：**
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```sql
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CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
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-- 避免在执行 SELECT email, name, created_at 时进行表查找（Table lookup）
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```
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**部分索引（Partial Index）：**
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```sql
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CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
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-- 索引体积更小，仅包含活动用户
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```
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**RLS 策略（已优化）：**
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```sql
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CREATE POLICY policy ON orders
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USING ((SELECT auth.uid()) = user_id); -- 包裹在 SELECT 中！
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```
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**UPSERT（更新插入）：**
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```sql
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INSERT INTO settings (user_id, key, value)
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VALUES (123, 'theme', 'dark')
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ON CONFLICT (user_id, key)
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DO UPDATE SET value = EXCLUDED.value;
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```
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**游标分页（Cursor Pagination）：**
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```sql
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SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
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-- O(1) 复杂度，对比 OFFSET 的 O(n) 复杂度
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```
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**队列处理：**
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```sql
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UPDATE jobs SET status = 'processing'
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WHERE id = (
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SELECT id FROM jobs WHERE status = 'pending'
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ORDER BY created_at LIMIT 1
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FOR UPDATE SKIP LOCKED
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) RETURNING *;
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```
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### 反模式（Anti-Pattern）检测
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```sql
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-- 查找未建立索引的外键
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SELECT conrelid::regclass, a.attname
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FROM pg_constraint c
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JOIN pg_attribute a ON a.attrelid = c.conrelid AND a.attnum = ANY(c.conkey)
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WHERE c.contype = 'f'
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AND NOT EXISTS (
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SELECT 1 FROM pg_index i
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WHERE i.indrelid = c.conrelid AND a.attnum = ANY(i.indkey)
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);
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-- 查找慢查询
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SELECT query, mean_exec_time, calls
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FROM pg_stat_statements
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WHERE mean_exec_time > 100
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ORDER BY mean_exec_time DESC;
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-- 检查表膨胀（Table bloat）
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SELECT relname, n_dead_tup, last_vacuum
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FROM pg_stat_user_tables
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WHERE n_dead_tup > 1000
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ORDER BY n_dead_tup DESC;
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```
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### 配置模板
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```sql
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-- 连接限制（根据 RAM 调整）
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ALTER SYSTEM SET max_connections = 100;
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ALTER SYSTEM SET work_mem = '8MB';
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-- 超时设置
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ALTER SYSTEM SET idle_in_transaction_session_timeout = '30s';
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ALTER SYSTEM SET statement_timeout = '30s';
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-- 监控
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CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
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-- 安全默认设置
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REVOKE ALL ON SCHEMA public FROM public;
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SELECT pg_reload_conf();
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```
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## 相关内容
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- 智能体（Agent）：`database-reviewer` - 完整的数据库审查工作流
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- 技能（Skill）：`clickhouse-io` - ClickHouse 分析模式
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- 技能（Skill）：`backend-patterns` - API 和后端模式
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---
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*基于 [Supabase Agent Skills](https://github.com/supabase/agent-skills) (MIT 许可证)*
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