MongoDB使用索引优化查询的方法

db.students.createIndex({ studentId: 1 });

db.students.createIndex({ lastName: 1, firstName: 1 });

db.students.find({ studentId: 12345 }).explain("executionStats");

db.students.createIndex({ status: 1 });
db.students.find({ status: "active" });

db.students.createIndex({ enrollmentDate: 1 });
db.students.find().sort({ enrollmentDate: 1 });

// 创建复合索引
db.students.createIndex({ lastName: 1, firstName: 1 });
// 查询可以使用索引的前缀部分
db.students.find({ lastName: "Smith" });

db.students.createIndex(
    { graduationYear: 1 },
    { partialFilterExpression: { status: "graduated" } }
);

// 创建包含需要返回字段的复合索引
db.students.createIndex({ studentId: 1, firstName: 1, lastName: 1 });
// 查询只读取索引中的字段
db.students.find({ studentId: 12345 }, { firstName: 1, lastName: 1, _id: 0 }).explain("executionStats");

db.students.createIndex({ studentId: 1 }, { unique: true });

db.students.createIndex({ email: 1 }, { sparse: true });

db.students.createIndex({ location: "2dsphere" });
db.students.find({
    location: {
        $near: {
            $geometry: {
                type: "Point",
                coordinates: [ -73.97, 40.77 ]
            }
        }
    }
});

db.students.reIndex();