I have a POC to do with JBPM6, and I saw the task "variables" (they are not so called variables) are accessible via taskService.getContent but is there a way to execute a search action to find tasks by variables values ?
I'm afraid that the binary persistence model seems not compatible for this feature.
You shouldn't use the binary information for that kind of searches. We recommend to externalize the engine data into a different storage/table so it can be consumed by SQL via the listeners. In that way you will be able to define how the data is stored for performance reasons. I will be writing a blog post about this soon. Stay tuned!