我的每个记录都具有以下数组类型的属性:
alpha, beta, gamma, delta, epsilon, zeta
我知道我可以找到数组中至少有一个组件的记录，如下所示:
db.accommodations.find({'alpha.1': {$exists: true}})
我希望能够在至少3个数组中找到至少有一个组件的记录.例如，可以找到以下记录:
alpha = []
beta = [1, 1, 1]
gamma = []
delta = [1, 1]
epsilon = []
zeta = [1]
但这不能:
alpha = []
beta = [1, 1, 1]
gamma = []
delta = [1, 1]
epsilon = []
zeta = []
我有办法吗？
查询
$size>=1$size is more general, if you only care for at least 1, you can also do $ne with [])$size>=3个文档通过aggregate(
[{"$match":
{"$expr":
{"$gte":
[{"$size":
{"$filter":
{"input":
["$alpha", "$beta", "$gamma", "$delta", "$epsilon", "$zeta"],
"cond": {"$gte": [{"$size": "$$this"}, 1]}}}},
3]}}}])