database 如何停止在 mongodb 集合中插入重复文档
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How to stop insertion of Duplicate documents in a mongodb collection
提问by shashank
Let us have a MongoDBcollection which has three docs..
让我们有一个MongoDB包含三个文档的集合..
db.collection.find()
db.collection.find()
{ _id:'...', user: 'A', title: 'Physics', Bank: 'Bank_A' }
{ _id:'...', user: 'A', title: 'Chemistry', Bank: 'Bank_B' }
{ _id:'...', user: 'B', title: 'Chemistry', Bank: 'Bank_A' }
We have a doc,
我们有一个文档，
doc = { user: 'B', title: 'Chemistry', Bank:'Bank_A' }
If we use
如果我们使用
db.collection.insert(doc)
here, this duplicate doc will get inserted in database.
在这里，这个重复的文档将被插入到数据库中。
{ _id:'...', user: 'A', title: 'Physics', Bank: 'Bank_A' }
{ _id:'...', user: 'A', title: 'Chemistry', Bank: 'Bank_B' }
{ _id:'...', user: 'B', title: 'Chemistry', Bank: 'Bank_A' }
{ _id:'...', user: 'B', title: 'Chemistry', Bank: 'Bank_A' }
How this duplicate can be stopped. On which field should indexing be done or any other approach?
如何停止这种重复。应该在哪个字段上进行索引或任何其他方法？
回答by Vic
Don't use insert.
不要使用插入。
Use update with upsert=true. Update will look for the document that matches your query, then it will modify the fields you want and then, you can tell it upsert:True if you want to insert if no document matches your query.
将更新与upsert=true. Update 将查找与您的查询匹配的文档，然后它会修改您想要的字段，然后，如果没有文档与您的查询匹配，您可以告诉它 upsert:True 如果要插入。
db.collection.update(
<query>,
<update>,
{
upsert: <boolean>,
multi: <boolean>,
writeConcern: <document>
}
)
So, for your example, you could use something like this:
因此，对于您的示例，您可以使用以下内容：
db.collection.update(doc, doc, {upsert:true})
回答by John Petrone
You should use a compound index on the set of fields that uniquely identify a document within your MongoDB collection. For example, if you decide that the combination of user, title and Bank are your unique key you would issue the following command:
您应该在唯一标识 MongoDB 集合中的文档的一组字段上使用复合索引。例如，如果您决定 user、title 和 Bank 的组合是您的唯一键，您将发出以下命令：
db.collection.createIndex( { user: 1, title: 1, Bank: 1 }, {unique:true} )
Please note that this should be done after you have removed previously stored duplicates.
请注意，这应该在您删除以前存储的重复项后完成。
http://docs.mongodb.org/manual/tutorial/create-a-compound-index/
http://docs.mongodb.org/manual/tutorial/create-a-compound-index/
http://docs.mongodb.org/manual/tutorial/create-a-unique-index/
http://docs.mongodb.org/manual/tutorial/create-a-unique-index/
回答by Creem
It has been updated from the above answers.
它已从上述答案更新。
please use db.collection.updateOne()instead of db.collection.update().
and also db.collection.createIndexes()instead of db.collection.ensureIndex()
请使用db.collection.updateOne()代替db.collection.update()。也db.collection.createIndexes()代替db.collection.ensureIndex()
Update:
the methods update() and ensureIndex() has been deprecated from mongodb 2.*, you can see more details in mongoand the path is ./mongodb/lib/collection.js.
For update(), the recommend methods are updateOne, updateMany, or bulkWrite.
For ensureIndex(), the recommend method is createIndexes.
更新：方法 update() 和 ensureIndex() 已从 mongodb 2.* 中弃用，您可以在mongo 中查看更多详细信息，路径为./mongodb/lib/collection.js. 对于update()，推荐的方法是updateOne, updateMany, or bulkWrite。对于ensureIndex()，推荐方法是createIndexes。
