如何避免Mongodb中的重複對象條目？

Question

現在在我的項目中，我使用了Play框架（JAVA）和Mongodb。我的收藏中有兩個字段，分別是哈希和地址。請注意，地址欄是一個對象。

我的收藏是這樣的：

db.hashed.find() 
{ "_id" : ObjectId("55f04cd0d4c68ef1211e6ee4"), "hash" : "1axuhWcqKB", "address" : { "floor" : 0, "block" : "5", "city" : "Mumbai", "state" : "ABC", "pincode" : 0, "latitude" : "77.6876", "longitude" : "13.57558", "hash" : "1axuhWcqKB" } } 
{ "_id" : ObjectId("55f04cd1d4c68ef1211e6ee6"), "hash" : "1ay4P407qF", "address" : { "floor" : 0, "block" : "5", "city" : "Mumbai", "state" : "ABC", "pincode" : 0, "latitude" : "77.6876", "longitude" : "13.57558", "hash" : "1ay4P407qF" } } 
{ "_id" : ObjectId("55f04cd2d4c68ef1211e6ee8"), "hash" : "1ayDn3Zemh", "address" : { "floor" : 0, "block" : "5", "city" : "Mumbai", "state" : "ABC", "pincode" : 0, "latitude" : "77.6876", "longitude" : "13.57558", "hash" : "1ayDn3Zemh" } } 

現在我思考，如何避免重複的地址條目，這顯然不應該獲得插入到數據庫中。我試圖通過地址字段確保索引，但看起來並不能解決這個問題。

> db.users.ensureIndex({"address" : 1},{unique: true}) 
{ 
"createdCollectionAutomatically" : false, 
"numIndexesBefore" : 2, 
"numIndexesAfter" : 2, 
"note" : "all indexes already exist", 
"ok" : 1 
} 

希望有人能幫助我解決這個問題。

Answer 1

我認爲問題出在地址子對象內的「散列」屬性。它們對於所有三行都不相同。這就是爲什麼mongodb不會將它們視爲重複鍵的原因。這是我的工作示例（wothout播放框架雖然，但它不會改變點）：

import java.util.LinkedHashMap; 
import java.util.Map; 

import org.jongo.Jongo; 
import org.jongo.MongoCollection; 

import com.mongodb.DB; 
import com.mongodb.MongoClient; 

public class MongodbTest { 
    public static void main(String[] args) throws Exception { 
     String tableName = "UniqueAddressTest"; 
     DB mdb = new MongoClient("localhost:27017").getDB(tableName); 
     Jongo jdb = new Jongo(mdb); 
     MongoCollection users = jdb.getCollection(tableName); 
     users.drop(); 
     users.ensureIndex("{address:1}", "{unique:true}"); 
     Map<String, Object> user1 = new LinkedHashMap<String, Object>(); 
     Map<String, Object> address1 = new LinkedHashMap<String, Object>(); 
     address1.put("floor", 0); 
     address1.put("block", "5"); 
     address1.put("city", "Mumbai"); 
     address1.put("state", "ABC"); 
     address1.put("pincode", 0); 
     address1.put("latitude", "77.6876"); 
     address1.put("longitude", "13.57558"); 
     address1.put("hash", "1axuhWcqKB"); 
     user1.put("address", address1); 
     users.insert(user1); 
     users.insert(user1); // Here is where duplicate key exception happens 
    } 
} 

[更新]如果您需要檢查地址的所有領域的獨特性，除了「哈希」你需要改變您的索引類似於：

users.ensureIndex("{address.floor:1, address.block:1, address.city:1, " + 
      "address.state:1, address.pincode:1, address.latitude:1, " + 
      "address.longitude:1}", "{name:\"unique_address\", unique:true}");