I've just discovered OLAP and it looks like a competing technology with
materialized views.
In a nutshell, OLAP seems to be "pre-storing" the results of potential
queries. When queries are made with those conditions, then the pre-stored
results are used. It seems most common for join conditions or aggregates
with conditions. (Corrections welcome...)
This seems like a generally useful tool. I expect PostgreSQL should one day
have a feature like this.
OLAP usage would basically be describing how the data fits together and
predicting what kinds of queries will be made. Then, internally the
implementation would decide what data should be cached. Perhaps it can do
some analysis of the data and the queries being run to come up with a fair
compromise.
Materialized Views are a simpler concept, but of limited usefulness. Having
a bunch of materialized views that are very similar would be less efficient
overall than having OLAP configured properly.
Questions:
(1) Has anyone been doing any work or serious thought on anything like this?
(2) Should I be focusing on OLAP rather than materialized views? With
materialized views, a few specific queries work really well, but related
queries get no benefit. Apparently, with OLAP, a whole class of queries
will get a huge boost. I'm not certain that OLAP and materialized views are
entirely different.
(3) I can't seem to find the paper on the twelve laws of OLAP, but it gets a
lot of mentioning. Does anyone know where I can obtain it?
Future Thoughts:
OLAP relies on knowing how the data fits together and what kinds of queries
are being done. It could be possible, just by analyzing the queries being
run, to have OLAP automatically kick in without user intervention.
--
Jonathan Gardner
jgardner@jonathangardner.net