Re: [Exist-development] optimizing positional predicates for fast paging

[Joe W. <jo...@gm...>]

Mike and Wolfgang,

A great topic!  I'd certainly welcome optimizations like this.  I
wonder:  If a FLWOR expression has an 'order by' clause, is it even
possible to optimize the expression's positional predicate (or
subsequence)?  Or does 'order by' make optimizations impossible?

>> collection("/")/ (//elem) [position() = (1 to 10)]
>
> Note that using subsequence instead of the predicate can be a lot
> faster sometimes.

I didn't realize that.  Can you generalize about when subsequence
would be faster?  And would you say it's always at least as fast as
the predicate?

Joe