Mongo aggregate not using index
My mongo search query uses an index, but the same functionality, if I implement using an aggregate, it doesn't use an index.
db.collection1.find({Attribute8: "s1000",Attribute9: "s1000"}).sort({Attribute10: 1})
"cursor used in search": "BtreeCursor Attribute8_1_Attribute9_1_Attribute10_1"
db.collection1.aggregate([
{
$match: {
Attribute8: "s1000",
Attribute9: "s1000"
}
},
{
$sort: {
Attribute10: 1
}
}
])
"cursor used in combination": "BtreeCursor".
Can someone tell me where this went wrong. My goal is to use indexes in an aggregated method. Thanks in advance.
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After some digging, the problem comes with limiting the use of the following types:
Symbol, MinKey, MaxKey, DBRef, Code and CodeWScope
In this case, Symbol is used to store a string value, so the index doesn't work.
Try with en set to explain true in the aggregate option.
[EDIT] My previous answer is wrong.
The aggregation pipeline uses "BtreeCursor" (only when the specified field has an index) to run the $ match query and uses the checked index, checks the "indexBound" to check.
Ensuring that the entire collection is indexed in "Attribute08"
db.temps.ensureIndex ({Attribute08: 1})
$ match on the field with index:
db.temps.aggregate ([{$ match: {Attribute08: "s1000"}}], {explain: true})
"allPlans": [
{
"cursor": "BtreeCursor",
"isMultiKey": false,
"scanAndOrder": false,
"indexBounds": {
"Attribute08": [
[
"s1000",
"s1000"
]
]
}
}
]
Below $ match in a field with no index:
db.temps.aggregate ([{$ match: {Attribute09: "s1000"}}], {explain: true})
"allPlans": [
{
"cursor": "BasicCursor",
"isMultiKey": false,
"scanAndOrder": false
}
]
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