Because Hadoop uses MapReduce to perform data queries, searches have to be done in batches. So, while you can perform highly detailed analysis of historical data, for instance, one area you would not want to use Hadoop for is transactional data. Transactional data, by its very nature, is highly complex and fluid, as a transaction on an ecommerce site can generate many steps that all have to be implemented quickly.
Nor would it be efficient for Hadoop to be used to process structured data sets that require very minimal latency, such as a Web site served up by a MySQL database in a typical LAMP stack. That’s a speed requirement that Hadoop would poorly serve.
Expanding supported query languages will be one area of focus for the Drill project. Another will be adding support for additional formats, such as JSON, since right now Dremel only supports the Google Protocol Buffer Format.