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我正在运行 MongoDB 4.2，请看下面我的文档的样子：

{
    "_id" : ObjectId("61e8e5b72e74b7fc3e16b632"),
    "1" : 2,
    "age_upon_outcome" : "1 year",
    "animal_id" : "A725717",
    "animal_type" : "Cat",
    "breed" : "Domestic Shorthair Mix",
    "color" : "Silver Tabby",
    "date_of_birth" : "2015-05-02",
    "datetime" : "2016-05-06 10:49:00",
    "monthyear" : "2016-05-06T10:49:00",
    "name" : "",
    "outcome_subtype" : "SCRP",
    "outcome_type" : "Transfer",
    "sex_upon_outcome" : "Spayed Female",
    "location_lat" : 30.6525984560228,
    "location_long" : -97.7419963476444,
    "age_upon_outcome_in_weeks" : 52.9215277777778
}

底线是我需要创建一个复合索引，以提高查询的性能，以查找具有“转移”的“结果类型”的品种，我不确定如何将下面的命令缩小到仅具有结果类型=转移

db.collection.createIndex( { breed: 1 } )
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1 回答 1

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会是这个：

db.collection.createIndex(
   { breed: 1 },
   { partialFilterExpression: { outcome_type: 'Transfer' } }
)
于 2022-01-20T06:48:48.243 回答