MongoDB 通过值匹配更新数组元素答案

【问题标题】：MongoDB updating an Array Element by value matchingMongoDB 通过值匹配更新数组元素
【发布时间】：2013-05-27 19:17:12
【问题描述】：

我有一个集合'locations'，我想用'united+states'替换'usa'。 DB目前的状态如下：

> db.locations.find({'country':'usa'})
{ "_id" : "boston", "country" : [ "usa" ], "server" : "", "ts" : 1369642586.077319, "type" : [ "city" ] }
{ "_id" : "chicago", "country" : [ "usa" ], "server" : "", "ts" : 1369642589.226037, "type" : [ "city" ] }
{ "_id" : "las+vegas", "country" : [ "usa" ], "server" : "", "ts" : 1369642591.688284, "type" : [ "city" ] }
{ "_id" : "los+angeles", "country" : [ "usa" ], "server" : "", "ts" : 1369642601.672113, "type" : [ "city" ] }
{ "_id" : "miami", "country" : [ "usa" ], "server" : "", "ts" : 1369642606.281971, "type" : [ "city" ] }
{ "_id" : "new+york", "country" : [ "usa" ], "server" : "", "ts" : 1369642611.884712, "type" : [ "city" ] }
{ "_id" : "portland", "country" : [ "usa" ], "server" : "", "ts" : 1369642615.59296, "type" : [ "city" ] }
{ "_id" : "san+francisco", "country" : [ "usa" ], "server" : "2", "ts" : 1369642619.255885, "type" : [ "city" ] }
{ "_id" : "san+jose", "country" : [ "usa" ], "server" : "", "ts" : 1369642622.74329, "type" : [ "city" ] }
{ "_id" : "seattle", "country" : [ "usa" ], "server" : "", "ts" : 1369642625.195549, "type" : [ "city" ] }
{ "_id" : "washington+dc", "country" : [ "usa" ], "server" : "", "ts" : 1369642628.37334, "type" : [ "city" ] }
{ "_id" : "cleveland", "country" : [ "usa" ], "server" : "2", "ts" : 1369642634.523065, "type" : [ "city" ] }
{ "_id" : "columbus", "country" : [ "usa" ], "server" : "2", "ts" : 1369642636.874618, "type" : [ "city" ] }
{ "_id" : "dallas", "country" : [ "usa" ], "server" : "2", "ts" : 1369642639.080141, "type" : [ "city" ] }
{ "_id" : "denver", "country" : [ "usa" ], "server" : "2", "ts" : 1369642642.236581, "type" : [ "city" ] }
{ "_id" : "houston", "country" : [ "usa" ], "server" : "2", "ts" : 1369642644.783804, "type" : [ "city" ] }
{ "_id" : "minneapolis", "country" : [ "usa" ], "server" : "2", "ts" : 1369642647.153817, "type" : [ "city" ] }
{ "_id" : "nashville", "country" : [ "usa" ], "server" : "2", "ts" : 1369642650.497276, "type" : [ "city" ] }
{ "_id" : "new+orleans", "country" : [ "usa" ], "server" : "2", "ts" : 1369642653.584663, "type" : [ "city" ] }
{ "_id" : "philadelphia", "country" : [ "usa" ], "server" : "2", "ts" : 1369642656.524054, "type" : [ "city" ] }

我运行了以下 MongoDB 查询，应该可以解决问题：

db.locations.update({'country':'usa'}, {'$set': {'country.$': 'united+states'}}, multi=true)

但是，这并没有达到预期的效果，并且 Collection 文档仍然有 'usa' 而不是 'united+states'。

【问题讨论】：

你有没有交叉检查。默认情况下，更新只更新一个文档，而不是所有匹配的文档。您的更新可能有效 - 只需检查 db.locations.count({'country':'usa'}) 在更新前后是否返回相同的值。

标签： mongodb mongodb-update

【解决方案1】：

您的更新调用中似乎有错字，请尝试以下操作：

db.locations.update({'country':'usa'}, {'$set': {'country.$': 'united+states'}}, {multi:true})

注意：options 现在是 {multi:true} 而不是 multi=true（或只是 true）

【讨论】：

【解决方案2】：

更新多个数组元素是不可能的，检查这个答案MongoDB update multiple records of array，如果他们是正确的，这可能会起作用

db.locations.find().forEach(function(doc) { 
    do { 
       db.locations.update({'country' : 'usa'}, 
       { $set : {'country.$' : 'united states'}}, true); 
    } while(db.getPrevError().n != 0); 
});

【讨论】：