Update Statistics with Distributions
Posted in 1998
I am running Informix Online 7.23.UC10 on a 4 Processor HP using HP UX 10.2.
I was trying to imrove performance of some particular programs and noticed that
"update statistics" was not being run regularly.
After running the appropriate "update statistics" on all tables, most queries
became extreamely slow. The "update statistics" I used was to update statistics
high with distributions for all columns that were the head of an index, and
update statistics low with distributions for all columns that were just part ofan index.
Most of my tests centered around two tables --- one with about 50,000 rows in
it, and the other with about 1.4 million rows in it.
The SQL Select statement joined 3 rows from the smaller table to about 60,000
rows of the larger table. The sqexplain.out file showed that an index was being
used to perform the join.
With distributions, this query took over 1.5 hours to run. Without
distributions, it runs in about 5 minutes!!!!!
With distributions on, it seems that the 3 CPU VP oninit process's get a huge
amount of CPU time during this 1.5 hour long run. I can see nothing else out of
the ordinary going on.
Has anybody ever had trouble with using distributions?
Any suggestions?
Thanks
___________________________________________________________
Jay Aymond
EXE Technologies
jay_aymond@exe.com