Where clause one query not being pushed down

Question

I am having a problem where I cannot get a certain "optional" parameter to be pushed down to a query. The parameter gets applied in memory after the result set is returned but not pushed down to the DB. The function is as follows:
declare function getFoo($key as xs:string, $optinalInput as xs:string*) as element(b:bar)*
for $foo in f:getFoo()
where $key = $foo/key
where not(exists($optinalInput)) or $foo/optional = $optinalInput<- does not get pushed down to the query
return $foo
If I make optinalInput an xs:string instead of xs:string * and the optional parameter will get pushed to the query. The problem is for this optional parameter I could get anywhere from 0-50 in the sequence. Seems like when the parameter is a sequence it doesn't get applied to the query. Is there any way around this?

Answer 1

Mike,
I understand the difference between * and ? and I was one of the people working on the "string-length not getting pushed" problem so I am very familiar with it. I tried you solution that you mentioned below and it still did not push the where clause to the query. I know I could achieve this with an ad-hoc query but I wanted to do a pure xquery implementation of this component because of the benefits it could have when interacting with other components in our ODSI project...such as SQL joining and potentially pushing additional where clause down from components that call this component. The only way I did get this to kind of work is to do this:
return
for $o in $optinalInput
for $foo in f:getFoo()
where $key = $foo/key
where $o = $foo/optional
return
$foo
for $count in 1
where not(exists($optinalInput))
for $foo in f:getFoo()
where $key = $foo/key
return
$foo
By putting the optional parameter into a FOR statement above the table call it guarantees that at least one will exists and that's why the optional parameter gets pushed properly to the DB with a parameterized query. The problem with this is that even though a parameterized query gets pushed it will call the SQL statement multiple times!...not good.
Another solution that was suggested to me would be to create the number of sequences for each item in the sequence and treat each item as it's own. For example if you know that the schema limits the sequence from 0..50 then you could make 50 items and 50 where clauses....probably not an optimal solution either but it would achieve properly pushing the where clause tot he DB.
For now I am satisfied with this optional parameter not being pushed to the DB because the performance was still good but it would be nice if there was a maintainable pure xquery solution to this problem.
Thanks for the help it's always appreciated!
Mike