What gains in typical query performance result from high-levels of compression? If the compression is three to five times, is the query speed-up proportionate?
A key value proposition is query performance. Speed depends on the data and the kinds of queries, however it should always be at least as fast as it is with standard databases and in many cases will be much faster. It is true that QD can compress source data by as much as 10 times, although three to five times is more common. In the 10x case, transferring the data off the disk would require about 90% less I/O transfer time. Despite that, the compression ratio is not necessarily directly related to query speed-up. Other factors can influence the speed-up, making it either faster or slower. Speed improvements are also achieved through the capture of the metadata. Additional performance enhancement is realized because the copy of the database that the user is accessing is local to his desktop or laptop. There is no contention for disks, CPU, memory, or other resources. The RDBMS does not incur any additional overhead from managing locks or simultaneous multiple user accesses.
