使用正则表达式时避免MongoDB性能问题
> db.demo531.createIndex({"CountryName":"text","Name":"text"});{
"createdCollectionAutomatically" : true,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
> db.demo531.insertOne({CountryName:"US","Name":"Chris"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8b2b60ef4dcbee04fbbbf2")
}
> db.demo531.insertOne({CountryName:"UK","Name":"David"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8b2b6cef4dcbee04fbbbf3")
}
> db.demo531.insertOne({CountryName:"AUS","Name":"chris"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8b2b74ef4dcbee04fbbbf4")
}
> db.demo531.insertOne({CountryName:"US","Name":"CHRIS"});{
"acknowledged" : true,
"insertedId" : ObjectId("5e8b2badef4dcbee04fbbbf5")
}在find()方法的帮助下显示集合中的所有文档-
> db.demo531.find();
这将产生以下输出-
{ "_id" : ObjectId("5e8b2b60ef4dcbee04fbbbf2"), "CountryName" : "US", "Name" : "Chris" }
{ "_id" : ObjectId("5e8b2b6cef4dcbee04fbbbf3"), "CountryName" : "UK", "Name" : "David" }
{ "_id" : ObjectId("5e8b2b74ef4dcbee04fbbbf4"), "CountryName" : "AUS", "Name" : "chris" }
{ "_id" : ObjectId("5e8b2badef4dcbee04fbbbf5"), "CountryName" : "US", "Name" : "CHRIS" }以下是使用正则表达式的查询-
> db.demo531.find({CountryName: "US", "Name": { "$regex": "chris", "$options": "i" }}).limit(4);这将产生以下输出-
{ "_id" : ObjectId("5e8b2b60ef4dcbee04fbbbf2"), "CountryName" : "US", "Name" : "Chris" }
{ "_id" : ObjectId("5e8b2badef4dcbee04fbbbf5"), "CountryName" : "US", "Name" : "CHRIS" }