Unstable explain plan

Database
Enthusiast

Unstable explain plan

Hi,

We have observed weird behavior in the Teradata environment , Basically some of the SQLs suddenly starts running slow and when checked and compared to the previous explain plan for which it ran with optimal efficiency , there was deviation in the number of steps and even the plan was slightly different.

 

 Did anyone ever faced similar situation? 

 

Thanks

1 REPLY
Supporter

Re: Unstable explain plan

Usualy you find this kind of behaviour in case of missing / stale stats.

And the cost based optimizer might decide to chose a different plan in case the demographics change. To an extreme one single additional row might change a plan...