我试图获取另一个集合中的对象数组中存在的元素的计数。
例子:
集合A:
{
_id:1,
name:"Sample1"
}
{
_id:2,
name:"Sample 2"
}
{
_id:3,
"name":"Sample 3"
}
{
_id:4,
"name":"Sample 4"
}
集合B:
{
_id:11,
items:[ {_id:1, name:"sample1",size:1},{_id:3, name:"sample 3",size:5}]
}
{
_id:12,
items:[ {_id:1, name:"sample1",size:2},{_id:3, name:"sample 3",size:6}]
}
{
_id:13,
items:[ {_id:2, name:"sample2", size:5},{_id:1, name:"sample 1",size:8}],
is_delete:true
}
{
_id:14,
items:[ {_id:1, name:"sample1",size:3},{_id:3, name:"sample 3",size:1}]
}
注意:items 中的 _id 是字符串。
预期输出:
{
_id:1,
name:"Sample1",
count:6
}
{
_id:2,
name:"Sample 2",
count:0
}
{
_id:3,
"name":"Sample 3",
"count":12
}
{
_id:4,
"name":"Sample 4",
"count":0
}
请帮我编写一个 mongo 查询以获得预期的输出。