> Still, shouldn't "Select * from <table> where 0=1" execution time be
> independant from the table's size ?

Firebird checks the where clause for each row of the table, that's why
it is slow. Using the PK makes it possible to look it up directly
using an index so that is faster.

That Firebird doesn't know that 0 will be different from 1 without
evaluating it for every row is actually helping those of us who
occationally want to prevent the optimizer from choosing one
particular plan.

I think you should take a look at the rdb$ tables. I may have done
something that could be of use for you, but I don't remember whether I
used SQL or methods that are part of IBO. Anyway, if I find the time
tomorrow I will have a look when I get to work.

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