Re: [Firebird-devel] Firebird feature requests

[Dmitry Y. <di...@us...>]

"Alex Kotov" <al_...@uk...> wrote:
>
> First of all I need a clarify my point a bit -- Firebird (1.5.2) reports
> that index _is_ used (i.e. you're correct) but query execution time is
> unacceptable.
>
> [snip]
>
> 5) Please execute both queries below and compare time of execution:
>    a) select recid from mytable where status = 0;
>    b) select recid from mytable where status < 1;

(status < 1) performs a range index scan looking for 0 and 1 values (i.e. 
the upper bound is strict). Values of 1 are eliminated later, after all 
corresponding records are fetched from cache/disk. For non-uniform data 
distribution, this may become a real performance issue. This is exactly what 
you observe. This is going to be improved in the future versions.


Dmitry