Question

在mongodb中，更新多个文档的写操作不是原子的。如果有3个记录A，B，C需要更新。

mongodb：

找到A，更新A，找到B，更新B，找到C，更新C

或

找到A，B，C并保存到内存，forEach，更新A，B，C？

Answer 1

MongoDB支持

Bulk Update。

请参阅此示例

db.mycollection.find()
{ "_id" : 1, "name" : "A", "designation" : "developer", "company" : "XYZ" }
{ "_id" : 2, "name" : "B", "designation" : "developer", "company" : "XYZ", "expe
rience" : 2 }
{ "_id" : 3, "name" : "C", "designation" : "developer", "company" : "XYZ", "expe
rience" : 3 }
{ "_id" : 4, "name" : "D", "designation" : "developer", "company" : "XYZ", "expe
rience" : 5 }
{ "_id" : 5, "name" : "E", "designation" : "Manager", "company" : "XYZ", "experi
ence" : 10 }
{ "_id" : 6, "name" : "F", "designation" : "Manager", "company" : "XYZ", "experi
ence" : 10 }
{ "_id" : 7, "name" : "G", "designation" : "Manager", "company" : "ABC", "experi
ence" : 10 }
{ "_id" : 8, "name" : "H", "designation" : "Developer", "company" : "ABC", "expe
rience" : 5 }
{ "_id" : 9, "name" : "I", "designation" : "Developer", "company" : "XYZ", "expe
rience" : 5 }

我将根据以下标准对mycollection进行批量更新

XYZ公司向其开发人员提供促销活动有高级开发人员5年的经验

我在Mongo shell中的命令是

var bulk = db.mycollection.initializeUnorderedBulkOp();

bulk.find({ $and:[{company:"XYZ"}, {experience:5}] }).update({$set:{designation:"
senior developer", comments:"Congrats you have been promoted to senior developer
"}});

bulk.execute();

Mongo Shell我们将在执行查询

后得到以下结果

BulkWriteResult({
        "writeErrors" : [ ],
        "writeConcernErrors" : [ ],
        "nInserted" : 0,
        "nUpserted" : 0,
        "nMatched" : 2,
        "nModified" : 2,
        "nRemoved" : 0,
        "upserted" : [ ]
})

符合我们公司条件的两份文件：＆＃34; XYZ＆＃34;和经验：5并更新了这些文件（_id：4，_id：9）

db.mycollection.find()

{ "_id" : 1, "name" : "A", "designation" : "developer", "company" : "XYZ" }
{ "_id" : 2, "name" : "B", "designation" : "developer", "company" : "XYZ", "expe
rience" : 2 }
{ "_id" : 3, "name" : "C", "designation" : "developer", "company" : "XYZ", "expe
rience" : 3 }
{ "_id" : 4, "name" : "D", "designation" : "senior developer", "company" : "XYZ"
, "experience" : 5, "comments" : "Congrats you have been promoted to senior deve
loper" }
{ "_id" : 5, "name" : "E", "designation" : "Manager", "company" : "XYZ", "experi
ence" : 10 }
{ "_id" : 6, "name" : "F", "designation" : "Manager", "company" : "XYZ", "experi
ence" : 10 }
{ "_id" : 7, "name" : "G", "designation" : "Manager", "company" : "ABC", "experi
ence" : 10 }
{ "_id" : 8, "name" : "H", "designation" : "Developer", "company" : "ABC", "expe
rience" : 5 }
{ "_id" : 9, "name" : "I", "designation" : "senior developer", "company" : "XYZ"
, "experience" : 5, "comments" : "Congrats you have been promoted to senior deve
loper" }

其他相关的有趣参考文献：

What's the difference between findAndModify and update in MongoDB?

https://docs.mongodb.com/manual/reference/method/Bulk.find.update/

https://docs.mongodb.com/manual/reference/method/db.collection.findAndModify/

https://docs.mongodb.com/v3.2/reference/method/db.collection.findOneAndUpdate/

希望它能帮助!!

mongodb是逐个查找和更新还是查找所有内容然后全部更新

1 个答案: