Subject Re: Upgrade to FB2.01 and performance drops
Author trtoms
--- In, "Adam" <s3057043@...> wrote:
> My bet is that your problem comes down to something simple.
> The 2.x optimiser is able to consider more paths than the 1.5.x
> optimiser. It can generate plans that the 1.5.x optimiser would not
> have even considered. This is usually a good thing. It means that
> queries that used to be slow may be able to run faster using the
> better plan. Occasionally though (perhaps due to bad statistics, or
> perhaps due to a bug or limitation in the optimiser), it either
> more credit to a bad plan than it is worth, or less credit to a good
> plan than it should have. This can lead to the wrong plan being
> The good news is that it is reasonably easy to trick the optimiser
> into thinking a specific index is irrelevant, so if you identify the
> problematic query and the plan it takes, a couple of minutes work
> make it at worst use the same plan as it used to.
> Adam

Thanks Adam. Looks like I'll need to find time to investigate the
issues on a "per query" basis. And that probably means sticking with
V1.5 for the time being...