云数据库联表查询过滤空数组怎么写

写了分组的结构（组非必填），组的数据如果被删除，联表后管理的字段也是空数组，我想要筛选非空数组的数据，要怎么写呢？

group分组表

{  
"bsonType": "object",  
"required": ["name"],  
"permission": {  
"read": true,  
"create": true,  
"update": true,  
"delete": true  
},  
"properties": {  
"_id": {  
"description": "ID，系统自动生成"  
},  
"name": {  
"bsonType": "string",  
"title": "组名"  
},  
"parent_id": {  
"bsonType": "string",  
"description": "上一级目录id",  
"parentKey": "_id"  
}  
}  
}

data数据表

{  
"bsonType": "object",  
"required": ["stream"],  
"permission": {  
"read": true,  
"create": true,  
"update": true,  
"delete": true  
},  
"properties": {  
"_id": {  
"description": "ID，系统自动生成"  
},  
"name": {  
"bsonType": "string",  
"description": "必须是字符串，并且是必需的",  
"title": "文件名"  
},  
"state": {  
"bsonType": "bool",  
"defaultValue": true,  
"description": "true代表正常。false代表被删除",  
"title": "文件状态"  
},  
"group_id": {  
"bsonType": "string",  
"title": "所属文件夹",  
"foreignKey": "group._id",  
"enumType": "tree",  
"enum": {  
"collection": "group",  
"orderby": "",  
"field": "_id as value, name as text"  
}  
},  
"upload_time": {  
"bsonType": "timestamp",  
"label": "时间",  
"forceDefaultValue": {  
"$env": "now"  
}  
}  
}  
}