我对 mongodb 很陌生,现在我需要计算 $lookup 字段,这可能吗?
我有这样的事情:
result = await company.aggregate([
{
$lookup: {
from: 'userFocus',
localField: '_id',
foreignField: 'value',
as: 'focusUsers'
}
},
{
$project:{
name: 1,
focusUsers: {userId: 1}
}
}
])
结果如下:
[
{_id: 'xxxx', name: 'first company', focusUsers: [user1, user2, user3...]},
{_id: 'yyyy', name: 'second company', focusUsers: []},
{_id: 'zzzz', name: 'third company', focusUsers: []}
]
现在我想要一个额外的列显示 focusUsers 计数,换句话说,我想要如下结果:
[
{_id: 'xxxx', name: 'first company', focusUsers: [user1, user2, user3], focusCount: 3},
{_id: 'yyyy', name: 'second company', focusUsers: [], focusCount: 0},
{_id: 'zzzz', name: 'third company', focusUsers: [], focusCount: 0}
]
是否可以?怎么做?请各位专家指教,先谢谢了!