The Daily WTF

NoSQL databases frequently are designed to shard or partition across many nodes. That, of course, makes enforcing unique IDs different than you might do in a SQL database. You can’t efficiently have an autoincrement sequence, and instead have to have something like a UUID.

But if you’ve designed your NoSQL database badly, or your input data isn’t well sanitized, you might find yourself in a situation where you can’t guarantee uniqueness without validating every row. That’s a bad place to be, but it’s probably how the code Remco found started its life.

The purpose of this Java code is to query all the customer IDs from a database and ensure that they’re fully unique.

private Completable validateUniqueCustomerIds(List<Container> rootContainers) { if (!validateUniqueIds) { log.trace(“validateUniqueCustomerIds validateUniqueIds == false -> skipping validation”); return Completable.complete(); } // use Flowable.share() to make sure we only call the repository once. final Flowable<String> nonEmptyCustomerIds = someMongoRepository.getCustomerIds()

To read the full article click on the 'post' link at the top.