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MongoDB how to deal with batch update violates the only constraint of key, I believe that many inexperienced people do not know what to do, so this article summarizes the causes of the problem and solutions, through this article I hope you can solve this problem.

MongoDB batch update generally uses upsert, but this update may violate the unique establishment constraint and result in no updates at all (the same is true for relational databases). In this case, you can update one by one or judge to update: rows that do not violate the unique constraint can be updated. Here is the way to deal with it, which can be used as a reference for those in need.

[background description]

Collection name: kk_device_likes_game

Unique index: {"device_id": 1

"target_type": 1

"target_id": 1

}

Updated as: db.kk_device_likes_game.update ({"target_type": 5, "target_id": NumberLong (1030)}, {"$set": {"target_id": NumberLong (1031)}}, true,true)

Change the target_id key value of "target_type": 5, "target_id": NumberLong (1030) from NumberLong (1030) to NumberLong (1031)

The update will fail because the collection update field has a compound unique index on it, making the updated key value conflict with other existing key values. As a result, keys that can be updated cannot be updated. The error is as follows:

[problem solving]

In view of the above situation: there are two ideas

Method 1: traverse the set of satisfying conditions and update them one by one

Idea: get the key value that meets the condition, traverse each of its _ id to update one by one, similar to sql is update. Where target_type=5 and target_id=1030 and _ id=...

The syntax is as follows:

Var cursor = db.kk_device_likes_game.find ({"target_type": 5, "target_id": NumberLong (1030)})

While (cursor.hasNext ()) {

Doc=cursor.next ()

A=db.kk_device_likes_game.update ({_ id:doc._id, "target_type": 5, "target_id": NumberLong (1030)}, {"$set": {"target_id": NumberLong (1031)}})

Print (a)

}

Method 2: judge not to update the row if the constraint is violated

Idea: get the key value that meets the condition, and compare the device_ id value with the device_id with the condition target_type=5 and target_id=1031 according to the compound unique index {"device_id": 1, "target_type": 1, "target_id": 1}. If there is the same device_id, the line is not updated. Similar to sql is update. Where target_type=5 and target_id=1030 and device_id not in (select device_id from where target_type=5 and target_id=1031)

The syntax is as follows:

Var cursor = db.kk_device_likes_game.find ({"target_type": 5, "target_id": NumberLong (1030)})

While (cursor.hasNext ()) {

Doc=cursor.next ()

A=db.kk_device_likes_game.find ({device_id:doc.device_id, "target_type": 5, "target_id": NumberLong (1031)}) .count ()

If (a = = 0) {

Db.kk_device_likes_game.update ({_ id:doc._id, "target_type": 5, "target_id": NumberLong (1030)}, {"$set": {"target_id": NumberLong (1031)}})

}

Else {

Print ("_ id:" + doc._id + "cannot be updated in violation of uniqueness constraint")

}

}

[self-check]

After the update, check whether the number of entries that meet the update conditions but are not updated is equal to the number of unique key entries that will be violated after the update. If equal, the update is successful.

View the number of entries that the update violates unique constraints:

ITunes 0

Var cursor = db.kk_device_likes_game.find ({"target_type": 5, "target_id": NumberLong (1030)})

While (cursor.hasNext ()) {

Doc=cursor.next ()

A=db.kk_device_likes_game.find ({device_id:doc.device_id, "target_type": 5, "target_id": NumberLong (1031)}) .count ()

I=i+a

}

The result is 431.

Check the number of entries that meet the update criteria but are not updated:

Db.kk_device_likes_game.find ({"target_type": 5, "target_id": NumberLong (1030)) .count ()

The result is 431.

The two results are the same, and this update is successful!

After reading the above, have you mastered how MongoDB deals with batch update key that violates unique constraints? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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