数据库 Schema 设计：经得起时间考验的模式

CREATE TABLE things (
    id          BIGSERIAL PRIMARY KEY,
    -- ... 业务列 ...
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- 面向 API 的资源
CREATE TABLE projects (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name        TEXT NOT NULL,
    owner_id    UUID NOT NULL REFERENCES users(id),
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
-- 内部映射表
CREATE TABLE project_members (
    id          BIGSERIAL PRIMARY KEY,
    project_id  UUID NOT NULL REFERENCES projects(id),
    user_id     UUID NOT NULL REFERENCES users(id),
    role        TEXT NOT NULL DEFAULT 'member',
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    UNIQUE (project_id, user_id)
);

-- 永远用这个
created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
 
-- 永远不要用这个
created_at  TIMESTAMP NOT NULL DEFAULT NOW()

CREATE OR REPLACE FUNCTION update_updated_at_column()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;
 
-- 对每个有 updated_at 的表应用
CREATE TRIGGER set_updated_at
    BEFORE UPDATE ON users
    FOR EACH ROW
    EXECUTE FUNCTION update_updated_at_column();
 
CREATE TRIGGER set_updated_at
    BEFORE UPDATE ON projects
    FOR EACH ROW
    EXECUTE FUNCTION update_updated_at_column();

CREATE TABLE customers (
    id              BIGSERIAL PRIMARY KEY,
    email           TEXT NOT NULL UNIQUE,
    display_name    TEXT NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE products (
    id              BIGSERIAL PRIMARY KEY,
    sku             TEXT NOT NULL UNIQUE,
    name            TEXT NOT NULL,
    price_cents     INTEGER NOT NULL,
    is_active       BOOLEAN NOT NULL DEFAULT true,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE orders (
    id              BIGSERIAL PRIMARY KEY,
    customer_id     BIGINT NOT NULL REFERENCES customers(id),
    status          TEXT NOT NULL DEFAULT 'pending'
                    CHECK (status IN ('pending', 'confirmed', 'shipped', 'delivered', 'cancelled')),
    total_cents     INTEGER NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE order_items (
    id              BIGSERIAL PRIMARY KEY,
    order_id        BIGINT NOT NULL REFERENCES orders(id) ON DELETE CASCADE,
    product_id      BIGINT NOT NULL REFERENCES products(id),
    quantity        INTEGER NOT NULL CHECK (quantity > 0),
    unit_price_cents INTEGER NOT NULL,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- 反范式化的报表表，由定时任务填充
CREATE TABLE order_reports (
    id                  BIGSERIAL PRIMARY KEY,
    order_id            BIGINT NOT NULL,
    customer_email      TEXT NOT NULL,
    customer_name       TEXT NOT NULL,
    product_names       TEXT[] NOT NULL,        -- 这里用数组没问题
    item_count          INTEGER NOT NULL,
    total_cents         INTEGER NOT NULL,
    order_status        TEXT NOT NULL,
    ordered_at          TIMESTAMPTZ NOT NULL,
    report_generated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE MATERIALIZED VIEW monthly_revenue AS
SELECT
    DATE_TRUNC('month', o.created_at) AS month,
    COUNT(DISTINCT o.id) AS order_count,
    SUM(o.total_cents) AS revenue_cents,
    COUNT(DISTINCT o.customer_id) AS unique_customers
FROM orders o
WHERE o.status != 'cancelled'
GROUP BY DATE_TRUNC('month', o.created_at)
ORDER BY month DESC;
 
-- 每晚刷新
REFRESH MATERIALIZED VIEW CONCURRENTLY monthly_revenue;

-- 永远这样做
ALTER TABLE orders
    ADD CONSTRAINT fk_orders_customer
    FOREIGN KEY (customer_id) REFERENCES customers(id);
 
-- "我们在代码里处理"的替代方案：
-- 靠希望。希望不是策略。

-- 有订单的客户不能被删除
ALTER TABLE orders
    ADD CONSTRAINT fk_orders_customer
    FOREIGN KEY (customer_id) REFERENCES customers(id)
    ON DELETE RESTRICT;

-- 删除订单会删除其行项——它们单独没有意义
ALTER TABLE order_items
    ADD CONSTRAINT fk_order_items_order
    FOREIGN KEY (order_id) REFERENCES orders(id)
    ON DELETE CASCADE;
 
-- 删除项目会删除其成员关系
ALTER TABLE project_members
    ADD CONSTRAINT fk_project_members_project
    FOREIGN KEY (project_id) REFERENCES projects(id)
    ON DELETE CASCADE;

-- 如果经理离职，其下属仍然存在——只是变成未分配
ALTER TABLE employees
    ADD CONSTRAINT fk_employees_manager
    FOREIGN KEY (manager_id) REFERENCES employees(id)
    ON DELETE SET NULL;

CREATE TABLE products (
    id              BIGSERIAL PRIMARY KEY,
    name            TEXT NOT NULL CHECK (LENGTH(name) > 0),
    price_cents     INTEGER NOT NULL CHECK (price_cents >= 0),
    discount_pct    NUMERIC(5,2) CHECK (discount_pct BETWEEN 0 AND 100),
    weight_kg       NUMERIC(10,3) CHECK (weight_kg > 0),
    status          TEXT NOT NULL CHECK (status IN ('draft', 'active', 'archived')),
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

ALTER TABLE users ADD CONSTRAINT uq_users_email UNIQUE (email);

-- 每个用户只能有一个活跃订阅（但可以有很多已取消的）
CREATE UNIQUE INDEX uq_active_subscription
    ON subscriptions (user_id)
    WHERE status = 'active';
 
-- 每个用户只能有一个主地址
CREATE UNIQUE INDEX uq_primary_address
    ON addresses (user_id)
    WHERE is_primary = true;

CREATE TABLE users (
    id          BIGSERIAL PRIMARY KEY,
    email       TEXT NOT NULL,
    display_name TEXT NOT NULL,
    is_active   BOOLEAN NOT NULL DEFAULT true,
    deleted_at  TIMESTAMPTZ,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
-- 部分索引：高效过滤已删除的行
CREATE INDEX idx_users_active ON users (email) WHERE deleted_at IS NULL;

-- 邮箱必须唯一，但只在非删除用户中
CREATE UNIQUE INDEX uq_users_email_active
    ON users (email)
    WHERE deleted_at IS NULL;

-- 软删除：面向用户，可恢复
CREATE TABLE documents (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    title       TEXT NOT NULL,
    content     TEXT NOT NULL,
    owner_id    UUID NOT NULL REFERENCES users(id),
    deleted_at  TIMESTAMPTZ,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE INDEX idx_documents_active ON documents (owner_id) WHERE deleted_at IS NULL;
 
-- 硬删除：内部使用，无法从 UI 恢复（但有审计记录）
CREATE TABLE api_keys (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id     UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    key_hash    TEXT NOT NULL,
    last_used_at TIMESTAMPTZ,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
-- 删除后就没了。audit_log 记录了它曾经存在过。

CREATE TABLE audit_log (
    id              BIGSERIAL PRIMARY KEY,
    table_name      TEXT NOT NULL,
    record_id       TEXT NOT NULL,          -- 用 text 以兼容 UUID 和 BIGINT 主键
    operation       TEXT NOT NULL CHECK (operation IN ('INSERT', 'UPDATE', 'DELETE')),
    old_values      JSONB,                  -- INSERT 时为 NULL
    new_values      JSONB,                  -- DELETE 时为 NULL
    changed_fields  TEXT[],                 -- 哪些列发生了变化（UPDATE 时）
    changed_by      UUID REFERENCES users(id),
    changed_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    ip_address      INET,
    user_agent      TEXT
);
 
CREATE INDEX idx_audit_log_table_record ON audit_log (table_name, record_id);
CREATE INDEX idx_audit_log_changed_by ON audit_log (changed_by);
CREATE INDEX idx_audit_log_changed_at ON audit_log (changed_at);

CREATE OR REPLACE FUNCTION audit_trigger_function()
RETURNS TRIGGER AS $$
DECLARE
    old_data JSONB;
    new_data JSONB;
    changed  TEXT[];
    col      TEXT;
BEGIN
    IF TG_OP = 'DELETE' THEN
        old_data := to_jsonb(OLD);
        INSERT INTO audit_log (table_name, record_id, operation, old_values, changed_at)
        VALUES (TG_TABLE_NAME, OLD.id::TEXT, 'DELETE', old_data, NOW());
        RETURN OLD;
    ELSIF TG_OP = 'UPDATE' THEN
        old_data := to_jsonb(OLD);
        new_data := to_jsonb(NEW);
        -- 找出变更的字段
        FOR col IN SELECT key FROM jsonb_each(new_data)
        LOOP
            IF old_data->col IS DISTINCT FROM new_data->col THEN
                changed := array_append(changed, col);
            END IF;
        END LOOP;
        -- 只在确实有变化时记录
        IF array_length(changed, 1) > 0 THEN
            INSERT INTO audit_log (table_name, record_id, operation, old_values, new_values, changed_fields, changed_at)
            VALUES (TG_TABLE_NAME, NEW.id::TEXT, 'UPDATE', old_data, new_data, changed, NOW());
        END IF;
        RETURN NEW;
    ELSIF TG_OP = 'INSERT' THEN
        new_data := to_jsonb(NEW);
        INSERT INTO audit_log (table_name, record_id, operation, new_values, changed_at)
        VALUES (TG_TABLE_NAME, NEW.id::TEXT, 'INSERT', new_data, NOW());
        RETURN NEW;
    END IF;
    RETURN NULL;
END;
$$ LANGUAGE plpgsql;
 
-- 对需要审计的表应用
CREATE TRIGGER audit_users
    AFTER INSERT OR UPDATE OR DELETE ON users
    FOR EACH ROW EXECUTE FUNCTION audit_trigger_function();
 
CREATE TRIGGER audit_orders
    AFTER INSERT OR UPDATE OR DELETE ON orders
    FOR EACH ROW EXECUTE FUNCTION audit_trigger_function();

-- 在你的应用中，执行查询之前：
SET LOCAL app.current_user_id = 'uuid-of-current-user';
 
-- 在触发器函数中：
changed_by_id := current_setting('app.current_user_id', true)::UUID;

CREATE TABLE documents (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    title           TEXT NOT NULL,
    content         TEXT NOT NULL,
    version         INTEGER NOT NULL DEFAULT 1,
    owner_id        UUID NOT NULL REFERENCES users(id),
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE document_history (
    id              BIGSERIAL PRIMARY KEY,
    document_id     UUID NOT NULL REFERENCES documents(id) ON DELETE CASCADE,
    title           TEXT NOT NULL,
    content         TEXT NOT NULL,
    version         INTEGER NOT NULL,
    changed_by      UUID REFERENCES users(id),
    changed_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    UNIQUE (document_id, version)
);

CREATE TABLE tenants (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name        TEXT NOT NULL,
    slug        TEXT NOT NULL UNIQUE,
    plan        TEXT NOT NULL DEFAULT 'free' CHECK (plan IN ('free', 'pro', 'enterprise')),
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE projects (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id   UUID NOT NULL REFERENCES tenants(id),
    name        TEXT NOT NULL,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TABLE tasks (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id   UUID NOT NULL REFERENCES tenants(id),
    project_id  UUID NOT NULL REFERENCES projects(id),
    title       TEXT NOT NULL,
    status      TEXT NOT NULL DEFAULT 'todo',
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
-- 每个索引都应该包含 tenant_id 以优化查询性能
CREATE INDEX idx_projects_tenant ON projects (tenant_id);
CREATE INDEX idx_tasks_tenant_project ON tasks (tenant_id, project_id);

-- 在表上启用 RLS
ALTER TABLE projects ENABLE ROW LEVEL SECURITY;
 
-- 基于会话变量创建策略
CREATE POLICY tenant_isolation ON projects
    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);
 
-- 即使是表所有者也强制 RLS
ALTER TABLE projects FORCE ROW LEVEL SECURITY;

-- 在你应用的连接中间件中：
SET LOCAL app.current_tenant_id = 'tenant-uuid-here';
 
-- 现在所有对启用了 RLS 的表的查询都会自动被过滤
SELECT * FROM projects;
-- PostgreSQL 内部添加：WHERE tenant_id = 'tenant-uuid-here'

-- 为每个租户创建 schema
CREATE SCHEMA tenant_acme;
CREATE SCHEMA tenant_globex;
 
-- 表放在租户的 schema 中
CREATE TABLE tenant_acme.projects (
    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name        TEXT NOT NULL,
    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
-- 设置当前租户的 search_path
SET search_path TO tenant_acme, public;
 
-- 现在不带限定符的查询会命中租户的 schema
SELECT * FROM projects;  -- 查询 tenant_acme.projects

CREATE TABLE products (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name            TEXT NOT NULL,
    category_id     UUID NOT NULL REFERENCES categories(id),
    price_cents     INTEGER NOT NULL CHECK (price_cents >= 0),
    attributes      JSONB NOT NULL DEFAULT '{}',
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
-- 示例数据：
-- 鞋子：{"size": "10", "color": "black", "material": "leather"}
-- 笔记本电脑：{"ram_gb": 16, "storage_gb": 512, "screen_inches": 14.0}

CREATE TABLE user_settings (
    user_id     UUID PRIMARY KEY REFERENCES users(id) ON DELETE CASCADE,
    preferences JSONB NOT NULL DEFAULT '{
        "theme": "system",
        "notifications": {"email": true, "push": false},
        "locale": "en",
        "timezone": "UTC"
    }',
    updated_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

-- 索引整个 JSONB 列（适用于 @> 包含查询）
CREATE INDEX idx_products_attributes ON products USING GIN (attributes);
 
-- 查询：找到所有 color = "black" 的产品
SELECT * FROM products
WHERE attributes @> '{"color": "black"}';
 
-- 查询：找到有这些属性中任何一个的产品
SELECT * FROM products
WHERE attributes ?| ARRAY['color', 'size'];

-- 索引一个特定路径
CREATE INDEX idx_products_color ON products ((attributes->>'color'));
 
-- 现在这就是一个普通的 B-tree 查找
SELECT * FROM products
WHERE attributes->>'color' = 'black';

-- 添加新列：干净、原子性、一条语句
ALTER TABLE products ADD COLUMN weight_kg NUMERIC(10,3);
 
-- 添加新 JSONB 字段：混乱，需要回填
UPDATE products
SET attributes = attributes || '{"weight_kg": null}'
WHERE NOT (attributes ? 'weight_kg');
-- 还得更新应用代码以处理缺失的 weight_kg
-- 还得更新验证逻辑
-- 还得更新每个包含 attributes 的 API 响应

-- 安全：仅元数据操作，瞬间完成（PostgreSQL 11+）
ALTER TABLE users ADD COLUMN bio TEXT;
ALTER TABLE users ADD COLUMN is_premium BOOLEAN NOT NULL DEFAULT false;
 
-- 危险：重写整张表，全表锁
ALTER TABLE users ALTER COLUMN email TYPE VARCHAR(500);
ALTER TABLE users ADD COLUMN score INTEGER NOT NULL DEFAULT compute_score();
 
-- 危险：扫描整张表进行验证
ALTER TABLE orders ADD CONSTRAINT check_total CHECK (total_cents >= 0);

-- 这会锁表并重写它。不要在大表上这么做。
ALTER TABLE users ADD COLUMN avatar_url TEXT NOT NULL DEFAULT 'https://example.com/default.png';

-- 迁移 1：添加 nullable 列
ALTER TABLE users ADD COLUMN normalized_email TEXT;

-- 迁移 2：分批回填（大表不要用一条语句搞定）
UPDATE users SET normalized_email = LOWER(TRIM(email))
WHERE normalized_email IS NULL
LIMIT 10000;
-- 重复直到所有行都被回填

-- 迁移 3：添加约束（用 NOT VALID 避免全表扫描，然后单独验证）
ALTER TABLE users ADD CONSTRAINT users_normalized_email_not_null
    CHECK (normalized_email IS NOT NULL) NOT VALID;
 
-- 迁移 4：验证约束（获取 ShareUpdateExclusiveLock，不是 AccessExclusiveLock）
ALTER TABLE users VALIDATE CONSTRAINT users_normalized_email_not_null;

-- 阻塞写入：不要在线上表这么做
CREATE INDEX idx_users_email ON users (email);
 
-- 非阻塞：用这个代替
CREATE INDEX CONCURRENTLY idx_users_email ON users (email);

-- 这就是查询逗号分隔值的方式。不要这样做。
SELECT * FROM posts WHERE tags LIKE '%react%';
-- 这也会匹配 "react-native" 和 "preact"
 
-- 我应该做的：
CREATE TABLE post_tags (
    post_id     UUID NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
    tag_id      UUID NOT NULL REFERENCES tags(id) ON DELETE CASCADE,
    PRIMARY KEY (post_id, tag_id)
);

CREATE TABLE posts (
    id      UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    title   TEXT NOT NULL,
    tags    TEXT[] NOT NULL DEFAULT '{}',
    -- ...
);
 
CREATE INDEX idx_posts_tags ON posts USING GIN (tags);
 
-- 干净的查询
SELECT * FROM posts WHERE 'react' = ANY(tags);
SELECT * FROM posts WHERE tags @> ARRAY['react', 'nextjs'];

-- 当时觉得没问题
CREATE TABLE notifications (
    id      BIGSERIAL PRIMARY KEY,
    type    TEXT NOT NULL,  -- "email", "sms", "push"
    -- ...
);
 
-- 然后你在任何 ORM 中试图查询它：
-- notification.type  ← 和每种语言的类型系统冲突
-- "type" 在大多数 SQL 方言中是保留字
-- 你到处都得加引号：SELECT "type" FROM notifications

-- 扩展
CREATE EXTENSION IF NOT EXISTS "pgcrypto";  -- 用于 gen_random_uuid()
 
-- updated_at 触发器函数（可复用）
CREATE OR REPLACE FUNCTION update_updated_at_column()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;
 
-- 租户
CREATE TABLE tenants (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name            TEXT NOT NULL CHECK (LENGTH(name) > 0),
    slug            TEXT NOT NULL UNIQUE CHECK (slug ~ '^[a-z0-9-]+$'),
    plan            TEXT NOT NULL DEFAULT 'free'
                    CHECK (plan IN ('free', 'pro', 'enterprise')),
    settings        JSONB NOT NULL DEFAULT '{}',
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE TRIGGER set_updated_at BEFORE UPDATE ON tenants
    FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();
 
-- 用户
CREATE TABLE users (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id       UUID NOT NULL REFERENCES tenants(id),
    email           TEXT NOT NULL,
    display_name    TEXT NOT NULL CHECK (LENGTH(display_name) > 0),
    password_hash   TEXT NOT NULL,
    is_active       BOOLEAN NOT NULL DEFAULT true,
    is_verified     BOOLEAN NOT NULL DEFAULT false,
    last_login_at   TIMESTAMPTZ,
    deleted_at      TIMESTAMPTZ,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE UNIQUE INDEX uq_users_email_per_tenant
    ON users (tenant_id, email)
    WHERE deleted_at IS NULL;
 
CREATE INDEX idx_users_tenant ON users (tenant_id) WHERE deleted_at IS NULL;
 
CREATE TRIGGER set_updated_at BEFORE UPDATE ON users
    FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();
 
-- 启用 RLS
ALTER TABLE users ENABLE ROW LEVEL SECURITY;
CREATE POLICY tenant_isolation ON users
    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);
 
-- 项目
CREATE TABLE projects (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id       UUID NOT NULL REFERENCES tenants(id),
    name            TEXT NOT NULL CHECK (LENGTH(name) > 0),
    description     TEXT NOT NULL DEFAULT '',
    status          TEXT NOT NULL DEFAULT 'active'
                    CHECK (status IN ('active', 'archived', 'deleted')),
    owner_id        UUID NOT NULL REFERENCES users(id),
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE INDEX idx_projects_tenant ON projects (tenant_id);
CREATE INDEX idx_projects_owner ON projects (owner_id);
 
CREATE TRIGGER set_updated_at BEFORE UPDATE ON projects
    FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();
 
ALTER TABLE projects ENABLE ROW LEVEL SECURITY;
CREATE POLICY tenant_isolation ON projects
    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);
 
-- 任务
CREATE TABLE tasks (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id       UUID NOT NULL REFERENCES tenants(id),
    project_id      UUID NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    title           TEXT NOT NULL CHECK (LENGTH(title) > 0),
    description     TEXT NOT NULL DEFAULT '',
    status          TEXT NOT NULL DEFAULT 'todo'
                    CHECK (status IN ('todo', 'in_progress', 'review', 'done')),
    priority        INTEGER NOT NULL DEFAULT 0 CHECK (priority BETWEEN 0 AND 4),
    assignee_id     UUID REFERENCES users(id) ON DELETE SET NULL,
    due_at          TIMESTAMPTZ,
    completed_at    TIMESTAMPTZ,
    sort_order      INTEGER NOT NULL DEFAULT 0,
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE INDEX idx_tasks_tenant_project ON tasks (tenant_id, project_id);
CREATE INDEX idx_tasks_assignee ON tasks (assignee_id) WHERE assignee_id IS NOT NULL;
CREATE INDEX idx_tasks_status ON tasks (tenant_id, status) WHERE status != 'done';
 
CREATE TRIGGER set_updated_at BEFORE UPDATE ON tasks
    FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();
 
ALTER TABLE tasks ENABLE ROW LEVEL SECURITY;
CREATE POLICY tenant_isolation ON tasks
    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);
 
-- 任务评论
CREATE TABLE task_comments (
    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id       UUID NOT NULL REFERENCES tenants(id),
    task_id         UUID NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
    author_id       UUID NOT NULL REFERENCES users(id),
    body            TEXT NOT NULL CHECK (LENGTH(body) > 0),
    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE INDEX idx_task_comments_task ON task_comments (task_id);
 
CREATE TRIGGER set_updated_at BEFORE UPDATE ON task_comments
    FOR EACH ROW EXECUTE FUNCTION update_updated_at_column();
 
ALTER TABLE task_comments ENABLE ROW LEVEL SECURITY;
CREATE POLICY tenant_isolation ON task_comments
    USING (tenant_id = current_setting('app.current_tenant_id')::UUID);
 
-- 审计日志（没有 RLS——仅管理员表）
CREATE TABLE audit_log (
    id              BIGSERIAL PRIMARY KEY,
    tenant_id       UUID NOT NULL REFERENCES tenants(id),
    table_name      TEXT NOT NULL,
    record_id       TEXT NOT NULL,
    operation       TEXT NOT NULL CHECK (operation IN ('INSERT', 'UPDATE', 'DELETE')),
    old_values      JSONB,
    new_values      JSONB,
    changed_fields  TEXT[],
    changed_by      UUID REFERENCES users(id),
    changed_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
 
CREATE INDEX idx_audit_log_tenant_table ON audit_log (tenant_id, table_name, record_id);
CREATE INDEX idx_audit_log_changed_at ON audit_log (changed_at);