--- In firebird-support@yahoogroups.com, "Adam" <s3057043@...> wrote:

>

<snip>

> 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

gives

> 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

selected.

>
> 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

can

> 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...

Trevor