Databases Reference
In-Depth Information
Figure 5.8
A simplified lattice.
bring the greatest gain are selected for materialization first, then in general, committing
even modest levels of disk space can bring marked improvements to query responses.
Committing larger amounts of disk space will in general bring quicker query response,
but with diminishing returns. Decide on a limit for the amount of disk space.
If you find that growth is pushing the disk space limit, there are options to extend
the usefulness, while remaining within your organization's means. For example, let's say
that management decides they want to track summary data for five years. You can con-
tinue to purge data from the base tables after say half a year, and at the same time main-
tain five years of historical data in the materialized views. Likewise, if a materialized
view containing fine-granularity data becomes too large, the details can be purged after
some appropriate amount of time, while summary views can continue to hold extended
