affaan-m/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;

配置模板

-- Connection limits (adjust for RAM)
ALTER SYSTEM SET max_connections = 100;
ALTER SYSTEM SET work_mem = '8MB';

-- Timeouts
ALTER SYSTEM SET idle_in_transaction_session_timeout = '30s';
ALTER SYSTEM SET statement_timeout = '30s';

-- Monitoring
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;

-- Security defaults
REVOKE ALL ON SCHEMA public FROM public;

SELECT pg_reload_conf();

相关

• 智能体：database-reviewer - 完整的数据库审查工作流
• 技能：clickhouse-io - ClickHouse 分析模式
• 技能：backend-patterns - API 和后端模式

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基于 Supabase 代理技能（致谢：Supabase 团队）（MIT 许可证）