Inconsistent Compiz performance

Question

Hi all,
I run both Ubuntu Hardy and Arch, and Compiz runs quite smoothly in the former (but I use it less so this might not be a valid point). I noticed however that when I refresh Compiz in my Arch installation (start Fusion-Icon, enable/disable loose-binding, etc.), animation performance would improve, but soon would regress to a very choppy state. The loose-binding/indirect rendering options don't matter; performance always improve when Compiz is refreshed, and regression cannot be prevented. I am using a Nvidia 8400 GS card.
I wonder if there's a way to keep that performance like it's always just refreshed? Is it the inner working of Compiz or my Nvidia card that leads to the performance regression? The choppiness really bugs me, especially when I know that my card can perform.

Answer 1

1. Identical execution plans are what caused the problem!
Imagine you have a table with 50,000 employees and 10 managers, you have a nice index on job type, and a query that selects the managers.
The execution plan will use the index and will run very fast.
Now add another 50,000 employees (acquisition!) and 10,000 managers.
If you didn't recollect statistics, the optimizer will assume that you still have 10 managers and will still use index (same plan!), but selecting 10,010 managers through index is much slower than selecting 10 managers through index, so - same plan, bad performance.
After you recollect stats - optimizer will know that you have 10,010 managers and will do full table scan to get them, which will be much faster than getting them through the index. So collecting stats will lead to better plan and better performance.