CODEWITHSUNDEEP
amazon-web-servicesamazon-dynamodb
Jordan
Jordan

Reputation: 2371

Ensure GSI isn't duplicated in DynamoDB

My DynamoDB table currently has the PK, SK and a GSI called "EmailIndex".

The idea behind this is that when users create their account, the username will be set as the PK and the email would be set as the EmailIndex GSI.

This should let me allow the user to login with either the username or the email.

Is it possible to reliably ensure there is no duplicated EmailIndex record? If for example, two different people enter the exact same email at the exact same time with different usernames, how can I ensure both users don't end up creating a record with the same GSI?

Right now I'm under the assumption that this isn't actually possible with DynamoDB. In which case, what would be the acceptable and recommended approach of allowing username or email logins instead of mandating one or the other?

Upvotes: 0

Views: 524

Answers (1)

Jason Wadsworth
Jason Wadsworth

Reputation: 8885

There isn't a way to guarantee unique values on a GSI. What I've done in the past to solve this is to have two records for the user, one with the data you have today, and one that is keyed on the email address. When doing a Put operation you can use a transaction to be sure both records succeed. You can still put the email in the GSI on the main record and use that for querying, or use the second record instead, and duplicate the data (which is what the GSI would do if you have the projection set to ALL).

Upvotes: 1

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