如何避免 Mongodb 中的重复对象条目？

Question

现在在我的项目中，我使用的是 Play 框架 (JAVA) 和 Mongodb。我的收藏中有两个字段，分别是哈希和地址。请注意，地址字段是一个对象。

我的收藏是这样的：

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" } } 

现在我正在考虑如何避免重复的地址条目，这显然不应该插入到数据库中。我尝试在地址字段上做 ensureindex，但看起来它不能解决这个问题。

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

希望有人可以帮助我解决这个问题。

Answer 1

我认为问题在于地址子对象内的“哈希”属性。它们对于所有三行都是不同的。这就是为什么 mongodb 不将它们视为重复键的原因。这是我的工作示例（虽然没有 Play 框架，但它并没有改变重点）：

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]如果您需要检查除“哈希”之外的所有地址字段的唯一性，您需要将索引更改为：

    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}");