Referential Integrity and HBase

Question

One of the first sample schemas you read about in the HBase FAQ is the Student-Course example for a many-many relationship. The schema has a Courses column in the Student table and a Students column in the Course table.

But I don't understand how in HBase you guarantee integrity between these two objects. If something were to crash between updating one table and before another, we'd have a problem.

I see there is a transaction facility, but what is the cost of using this on what might be every Put? Or are there other ways to think about the problem?

Answer 1

If you have to perform two INSERTs as a single unit of work, that means you have to use a transaction manager to preserve ACID properties. There's no other way to think about the problem that I know of.

The cost is less of a concern that referential integrity. Code it properly and don't worry about performance. Your code will be the first place to look for performance problems, not the transaction manager.

Answer 2

Without an additional log you won't be able to guarantee integrity between these two objects. HBase only has atomic updates at the row level. You could probably use that property though to create a Tx log that could recover after a failure.