Databases Reference
In-Depth Information
5
Selecting Materialized
Views
For seven and a half million years, Deep Thought computed and calculated,
and in the end announced that the answer was in fact Forty-two—and
so another, even bigger, computer had to be built to find out what
the actual question was.
—
The Restaurant at the End of the Universe,
by Douglas Adams
Our philosophy starts with the premise that a result is a terrible thing to waste
and that its generation cost should be amortized over multiple uses of the result.
—Kotidis and Roussopoulos, inventors of the
DynaMat view management system
hat is the answer to life, the universe, and everything? That is the question posed
to Deep Thought in
The Hitchhiker's Guide to the Galaxy
by Douglas Adams.
The question tied up Deep Thought for seven and a half million years. We tend not to
ask such profound questions of our databases, but we do hope to find meaningful
answers in a reasonable amount of time. If our query analyzer tells us a query will take
seven and a half million years to run, we should probably look for a better solution. This
chapter explores the use of materialized views to speed up query responses.
Make the common case fast. A large number of queries are posed against our data-
base every day. There tend to be many queries that occur a few times, and a few queries
that occur frequently. We have a database in third normal form (3NF). Some of the
tables are rather large in terms of the number of disk blocks utilized. Accessing and join-
W
71
