No bits left behind

One of the key tenets of database system design is making efficient use of storage and memory resources. However, existing database system implementations are actually extremely wasteful of such resources; for example, most systems leave a great deal of empty space in tuples, index pages, and data pages, and spend many CPU cycles reading cold records from disk that are never used. In this paper, we identify a number of such sources of waste, and present a series of techniques that limit this waste (e.g., forcing better memory locality for hot data and using empty space in index pages to cache popular tuples) without substantially complicating interfaces or system design. We show that these techniques effectively reduce memory requirements for real scenarios from the Wikipedia database (by up to 17.8×) while increasing query performance (by up to 8×).