Updated
该聚合将设置的值skill_score
to 0
if _skills
不存在,则使用$redact https://docs.mongodb.com/manual/reference/operator/aggregation/redact/#pipe._S_redact删除具有以下内容的子文档skill_score
等于0
:
db.project_if.aggregate([
{
$unwind: {
path: '$_skills',
preserveNullAndEmptyArrays: true,
}
},
{
$project: {
_skills: {
label: '$_skills',
skill_score: {
$cond: {
if: {
$eq: ['$_skills', undefined]
},
then: 0,
else: 1,
}
}
}
}
},
{
$redact: {
$cond: {
if: { $eq: [ "$skill_score", 0 ] },
then: '$$PRUNE',
else: '$$DESCEND'
}
}
}
]);
结果会是这样的:
[
{ "_id" : '', "_skills" : { "label" : "skill1", "skill_score" : 1 } },
{ "_id" : '', "_skills" : { "label" : "skill2", "skill_score" : 1 } },
{ "_id" : '' },
]