{
    "table_name": "approval_instance",
    "fields": [
        {"name": "id", "type": "varchar(32)", "not_null": true, "comment": "主键ID"},
        {"name": "workflow_id", "type": "varchar(32)", "not_null": true, "comment": "工作流ID"},
        {"name": "business_type", "type": "varchar(50)", "not_null": true, "comment": "业务类型: contract/customer/opportunity"},
        {"name": "business_id", "type": "varchar(64)", "not_null": true, "comment": "业务记录ID"},
        {"name": "current_step", "type": "int", "comment": "当前步骤号"},
        {"name": "status", "type": "varchar(20)", "comment": "状态: pending/approved/rejected/cancelled"},
        {"name": "initiator_id", "type": "varchar(32)", "comment": "发起人ID"},
        {"name": "org_id", "type": "varchar(32)", "comment": "组织ID"},
        {"name": "initiated_at", "type": "timestamp", "comment": "发起时间"},
        {"name": "completed_at", "type": "timestamp", "comment": "完成时间"}
    ],
    "indexes": [
        {"name": "idx_instance_workflow", "fields": ["workflow_id"], "type": "normal"},
        {"name": "idx_instance_business", "fields": ["business_type", "business_id"], "type": "normal", "comment": "复合索引：按业务类型和记录查询"},
        {"name": "idx_instance_status", "fields": ["status"], "type": "normal"},
        {"name": "idx_instance_initiator", "fields": ["initiator_id"], "type": "normal"}
    ],
    "codes": [
        {"key": "pending", "name": "审批中"},
        {"key": "approved", "name": "已通过"},
        {"key": "rejected", "name": "已驳回"},
        {"key": "cancelled", "name": "已取消"}
    ]
}