Why is MongoDB using scanAndOrder here?

I save game files in MongoDB. Among other things, the documents contain the player’s name (name), the end time of the game (endMS) and the type of game (type). A type can have one of five different values.

I need to search for all finished games by a player sorted by the end time of the game and for all finished games by a player with a certain type of game, also sorted by the end time of the game.

Examples for both queries:

db.games.find ({name: "Stefan", endMS: {$ Gt: 0}}). Sorts ({endMS: -1})

and

db.games.find ({name: "Stefan", type: "li", endMS: {$ Gt: 0}}). Sorts ({endMS: -1})

You can use indexes

db.games.ensureIndex ({name: 1, endMS: -1})

and

db.games.ensureIndex ({name: 1, type: 1, endMS: -1})

for quick access.

:

db.games.ensureIndex({: 1, endMS: -1, : 1})

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db.games.find({: "" , : "", endMS: {$ Gt: 0}}) ({endMS: -1}).. ()

{
    "cursor" : "BtreeCursor name_1_endMS_-1_type_1",
    "isMultiKey" : false,
    "n" : 1,
    "nscannedObjects" : 1,
    "nscanned" : 22,
    "nscannedObjectsAllPlans" : 4,
    "nscannedAllPlans" : 25,
    "scanAndOrder" : true,
    "indexOnly" : false,
    "nYields" : 0,
    "nChunkSkips" : 0,
    "millis" : 0,
    "indexBounds" : {
        "name" : [
            [
                "Stefan",
                "Stefan"
            ]
        ],
        "endMS" : [
            [
                Infinity,
                0
            ]
        ],
        "type" : [
            [
                "bli",
                "bli"
            ]
        ]
    },
    "server" : "localhost:27017",
    "filterSet" : false
}

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