danyschaer wrote:

>
> I am using FB 2.1, and I have found that LPAD slows down (60 seconds or
> more for 30k records) a lot when used in a order by clause:
>
> select "EXP1" from "PROC" order by LPAD(lower(trim("EXP1")),18)
>
> or
>
> select LPAD(lower(trim("EXP1")),18) as "XX" from "PROC" order by "XX"
>
> But, it is very fast (0 seconds) if I do not use it in the order by
> clause:
>
> select LPAD(lower(trim("EXP1")),18) from "PROC"
>
> Why is this?.

Regardless of its last argument value, LPAD/RPAD returns VARCHAR(32K) as
a result. Sorting works with full record lengths. So, for 30K records,
the engine has to sort 900MB.


Dmitry