ndhananj 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
基于 Supabase Agent Skills (MIT License)