affaan-m
PostgreSQL database patterns for query optimization, schema design, indexing, and security. Based on Supabase best practices.
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PostgreSQL 最佳實務快速參考。詳細指南請使用 database-reviewer agent。
| 查詢模式 | 索引類型 | 範例 |
|---|---|---|
WHERE col = value | B-tree（預設） | CREATE INDEX idx ON t (col) |
WHERE col > value | B-tree | CREATE INDEX idx ON t (col) |
WHERE a = x AND b > y |
| 複合 |
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) |
| 時間序列範圍 | BRIN | CREATE INDEX idx ON t USING brin (col) |
| 使用情況 | 正確類型 | 避免 |
|---|---|---|
| IDs | bigint | int、隨機 UUID |
| 字串 | text | varchar(255) |
| 時間戳 | timestamptz | timestamp |
| 金額 | numeric(10,2) | float |
| 旗標 | boolean | varchar、int |
複合索引順序：
-- 等值欄位優先，然後是範圍欄位
CREATE INDEX idx ON orders (status, created_at);
-- 適用於：WHERE status = 'pending' AND created_at > '2024-01-01'
覆蓋索引：
CREATE INDEX idx ON users (email) INCLUDE (name, created_at);
-- 避免 SELECT email, name, created_at 時的表格查詢
部分索引：
CREATE INDEX idx ON users (email) WHERE deleted_at IS NULL;
-- 更小的索引，只包含活躍使用者
RLS 政策（優化）：
CREATE POLICY policy ON orders
USING ((SELECT auth.uid()) = user_id); -- 用 SELECT 包裝！
UPSERT：
INSERT INTO settings (user_id, key, value)
VALUES (123, 'theme', 'dark')
ON CONFLICT (user_id, key)
DO UPDATE SET value = EXCLUDED.value;
游標分頁：
SELECT * FROM products WHERE id > $last_id ORDER BY id LIMIT 20;
-- O(1) vs OFFSET 是 O(n)
佇列處理：
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 *;
-- 找出未建索引的外鍵
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)
);
-- 找出慢查詢
SELECT query, mean_exec_time, calls
FROM pg_stat_statements
WHERE mean_exec_time > 100
ORDER BY mean_exec_time DESC;
-- 檢查表格膨脹
SELECT relname, n_dead_tup, last_vacuum
FROM pg_stat_user_tables
WHERE n_dead_tup > 1000
ORDER BY n_dead_tup DESC;
-- 連線限制（依 RAM 調整）
ALTER SYSTEM SET max_connections = 100;
ALTER SYSTEM SET work_mem = '8MB';
-- 逾時
ALTER SYSTEM SET idle_in_transaction_session_timeout = '30s';
ALTER SYSTEM SET statement_timeout = '30s';
-- 監控
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
-- 安全預設值
REVOKE ALL ON SCHEMA public FROM public;
SELECT pg_reload_conf();
database-reviewer - 完整資料庫審查工作流程clickhouse-io - ClickHouse 分析模式backend-patterns - API 和後端模式基於 Supabase Agent Skills（MIT 授權）
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