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postgres-patterns

tessl i github:ysyecust/everything-claude-code --skill postgres-patterns

PostgreSQL database patterns for query optimization, schema design, indexing, and security. Based on Supabase best practices.

69%

Overall

Validation — 69%

Implementation — 88%

Activation — 33%

SKILL.md

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PostgreSQL 模式

PostgreSQL 最佳實務快速參考。詳細指南請使用 database-reviewer agent。

何時啟用

撰寫 SQL 查詢或 migrations
設計資料庫 schema
疑難排解慢查詢
實作 Row Level Security
設定連線池

快速參考

索引速查表

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)`

資料類型快速參考

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`

常見模式

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 *;

反模式偵測

-- 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;

設定範本

-- 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();