Oracle Fun with Predicate pushdown

I had some fun recently with a Oracle database choosing a poor execution plan.

The problem was with a view which had a column which was explicitly cast to a value.

For example:

create table vw_temp
as
select
cast(ID) as NUMBER(19,0) as ID,
Name varchar2(50)
from very_large_table a
join large_table b on a.ID = b.ID
where Name = 'whatever' ;

Oracle in this case was unable to use the ability to push predicates down and make the joins more optimized.

So the moral of the story is be careful if you are doing casts/converts or any function which will change the column in a view.

Have Fun

For more info about predicate push down have a read of this blog entry
https://blogs.oracle.com/optimizer/entry/basics_of_join_predicate_pushdown_in_oracle
Or this short entry in the documenation
http://www.oracle.com/pls/db102/to_URL?remark=ranked&urlname=http:%2F%2Fdownload.oracle.com%2Fdocs%2Fcd%2FB19306_01%2Fserver.102%2Fb14211%2Foptimops.htm%23i55050

Oracle RAC on EC2 redux

I was reading some RSS feeds the other day and noticed that Jeremy Schneider over at Ardent Performance Computing was working on getting Oracle RAC working on Amazon EC2.
http://www.ardentperf.com/2011/03/04/byo-oracle-rac-on-ec2/
He looks to have solved the whole Virtual IP issue by using another instance. Nice solution!

When I get a spare moment (don't believe for a minute that the lack of posts means I am not busy) it would be good to take the scripts and get the whole Oracle RAC working in Amazon EC2 finally!

Other News:

I have had the chance to play with some columnar databases, Vertica and Ingres VectorWise and the performance is good. I used the TPC-H benchmark to test to a scale 20 (small only due to a lack of disk space). So the results are nothing like the recent Scale 100 benchmarks that Ingres VectorWise did but useful nonetheless. Sadly I can't publish any scripts or results as the IP is owned by my current employer.

Currently I am focused on improving my skills in predictive modeling and analytics. This is using the data rather than just supporting/recovering and hand-holding the data a.k.a. being a DBA.

Listening to trance, in the zone and most definitely Having Fun!

Paul