CODEWITHSUNDEEP
mongodbdata-integrity
Tommz
Tommz

Reputation: 3453

Where to handle errors on database in mongoDB?

When user is registering on website, e-mail needs to be provided which is unique. I've made unique index on schema's email attribute, so if I try to save the document in database, error with code 11000 will be returned. My question is, regarding to business layer and data layer, should I just pass the document to database and catch/check error codes which it returns or should I check if the user with that e-mail exists before? I've being told that data integrity should be checked before passing it to the database by the business layer, but I don't see the reason why should I do that since I believe that mongo would be much faster raising the exception itself since it has that index provided. The only disadvantage I see in error code checking is that error codes might change (but I could abstract them) and the syntax might be changed.

Upvotes: 1

Views: 100

Answers (2)

Bob Kuhar
Bob Kuhar

Reputation: 11140

There is the practical matter of speed and the fragility of "check-then-set" systems. If you try and check if an email exists before you write the document keyed on email, there is a chance that between the time you check and the time you right the conditions of the unique index are met and your write fails anyhow. This is a classic race condition. Further, it takes 2 queries to do check-then-set but only 1 query to do the insert and handle the failure. In my application I am having success with just letting the failure occur and reacting to the result.

Upvotes: 1

Sammaye
Sammaye

Reputation: 43884

As @JamesWahlin says, it is the difference between dong this all in one or causing mixed results (along with the index check) from potential race conditions by adding the extra client read.

Definitely rely on the response of only insert from MongoDB here.

Upvotes: 1

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