我有以下查询。
db.getCollection('logs').find({'uid.$id': {
'$in': [
ObjectId("580e3397812de36b86d68c04"),
ObjectId("580e33a9812de36b86d68c0b"),
ObjectId("580e339a812de36b86d68c09"),
ObjectId("580e339a812de36b86d68c08"),
ObjectId("580e33a9812de36b86d68c0a"),
ObjectId("580e33bd812de36b86d68c11"),
ObjectId("580e33c0812de36b86d68c13")
]}, levelno: { '$gte': 10 }
}).sort({_id: 1})
这应该返回 1847 个文档。但是，执行时，只得到1000个文档，也就是游标的batchSize，然后游标关闭(将其cursorId设置为0)，就好像所有的文档都返回了一样.
如果我去掉排序，那么我得到所有 1847 个文档。
所以我的问题是，为什么在使用 $in 运算符进行排序时它会悄无声息地失败？
编辑
使用 explain 给出以下输出
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "session.logs",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"levelno" : {
"$gte" : 10
}
},
{
"uid.$id" : {
"$in" : [
ObjectId("580e3397812de36b86d68c04"),
ObjectId("580e339a812de36b86d68c08"),
ObjectId("580e339a812de36b86d68c09"),
ObjectId("580e33a9812de36b86d68c0a"),
ObjectId("580e33a9812de36b86d68c0b"),
ObjectId("580e33bd812de36b86d68c11"),
ObjectId("580e33c0812de36b86d68c13")
]
}
}
]
},
"winningPlan" : {
"stage" : "SORT",
"sortPattern" : {
"_id" : 1
},
"inputStage" : {
"stage" : "SORT_KEY_GENERATOR",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"uid.$id" : 1,
"levelno" : 1,
"_id" : 1
},
"indexName" : "uid.$id_1_levelno_1__id_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"uid.$id" : [
"[ObjectId('580e3397812de36b86d68c04'), ObjectId('580e3397812de36b86d68c04')]",
"[ObjectId('580e339a812de36b86d68c08'), ObjectId('580e339a812de36b86d68c08')]",
"[ObjectId('580e339a812de36b86d68c09'), ObjectId('580e339a812de36b86d68c09')]",
"[ObjectId('580e33a9812de36b86d68c0a'), ObjectId('580e33a9812de36b86d68c0a')]",
"[ObjectId('580e33a9812de36b86d68c0b'), ObjectId('580e33a9812de36b86d68c0b')]",
"[ObjectId('580e33bd812de36b86d68c11'), ObjectId('580e33bd812de36b86d68c11')]",
"[ObjectId('580e33c0812de36b86d68c13'), ObjectId('580e33c0812de36b86d68c13')]"
],
"levelno" : [
"[10.0, inf.0]"
],
"_id" : [
"[MinKey, MaxKey]"
]
}
}
}
}
},
"rejectedPlans" : [
{
"stage" : "SORT",
"sortPattern" : {
"_id" : 1
},
"inputStage" : {
"stage" : "SORT_KEY_GENERATOR",
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"levelno" : 1,
"_id" : 1,
"uid.$id" : 1
},
"indexName" : "levelno_1__id_1_uid.$id_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"levelno" : [
"[10.0, inf.0]"
],
"_id" : [
"[MinKey, MaxKey]"
],
"uid.$id" : [
"[ObjectId('580e3397812de36b86d68c04'), ObjectId('580e3397812de36b86d68c04')]",
"[ObjectId('580e339a812de36b86d68c08'), ObjectId('580e339a812de36b86d68c08')]",
"[ObjectId('580e339a812de36b86d68c09'), ObjectId('580e339a812de36b86d68c09')]",
"[ObjectId('580e33a9812de36b86d68c0a'), ObjectId('580e33a9812de36b86d68c0a')]",
"[ObjectId('580e33a9812de36b86d68c0b'), ObjectId('580e33a9812de36b86d68c0b')]",
"[ObjectId('580e33bd812de36b86d68c11'), ObjectId('580e33bd812de36b86d68c11')]",
"[ObjectId('580e33c0812de36b86d68c13'), ObjectId('580e33c0812de36b86d68c13')]"
]
}
}
}
}
},
{
"stage" : "FETCH",
"filter" : {
"$and" : [
{
"levelno" : {
"$gte" : 10
}
},
{
"uid.$id" : {
"$in" : [
ObjectId("580e3397812de36b86d68c04"),
ObjectId("580e339a812de36b86d68c08"),
ObjectId("580e339a812de36b86d68c09"),
ObjectId("580e33a9812de36b86d68c0a"),
ObjectId("580e33a9812de36b86d68c0b"),
ObjectId("580e33bd812de36b86d68c11"),
ObjectId("580e33c0812de36b86d68c13")
]
}
}
]
},
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"_id" : 1
},
"indexName" : "_id_",
"isMultiKey" : false,
"isUnique" : true,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"_id" : [
"[MinKey, MaxKey]"
]
}
}
}
]
},
"ok" : 1
}
最佳答案
发生的事情是这个排序查询必须在内存中执行，因为它不受索引支持，这将结果限制为 32 MB。此行为已记录 here ，用 JIRA 解决这个问题 here .
此外，您不能定义索引来支持此查询，因为您正在对不属于查询的字段进行排序，并且这些情况都不适用:
If the sort keys correspond to the index keys or an index prefix, MongoDB can use the index to sort the query results. A prefix of a compound index is a subset that consists of one or more keys at the start of the index key pattern.
...
An index can support sort operations on a non-prefix subset of the index key pattern. To do so, the query must include equality conditions on all the prefix keys that precede the sort keys.
您应该能够通过使用聚合框架来解决该限制，如果需要，可以通过 allowDiskUse: true 选项指示聚合框架使用临时文件作为其管道阶段输出:
db.getCollection('logs').aggregate([
{$match: {'uid.$id': {
'$in': [
ObjectId("580e3397812de36b86d68c04"),
ObjectId("580e33a9812de36b86d68c0b"),
ObjectId("580e339a812de36b86d68c09"),
ObjectId("580e339a812de36b86d68c08"),
ObjectId("580e33a9812de36b86d68c0a"),
ObjectId("580e33bd812de36b86d68c11"),
ObjectId("580e33c0812de36b86d68c13")
]}, levelno: { '$gte': 10 }
}},
{$sort: {_id: 1}}
], { allowDiskUse: true })
关于mongodb - 使用 $in 排序不返回所有文档，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40285599/