Searching and sorting over multiple collections

[Per Steffensen]

Hi

Due to what we have seen in recent tests I got in doubt how Solr search 
is actually supposed to behave

* Searching with 
"distrib=true&q=*:*&rows=10&collection=x,y,z&sort=timestamp asc"
** Is Solr supposed to return the 10 documents with the lowest timestamp 
across all documents in all slices of collection x, y and z, or is it 
supposed to just pick 10 random documents from those slices and just 
sort those 10 randomly selected documents?
** Put in another way - is this search supposed to be consistent, 
returning exactly the same set of documents when performed several times 
(no documents are updated between consecutive searches)?

* A search returns a "numFound"-field telling how many documents all in 
all matches the search-criteria, even though not all those documents are 
returned by the search. It is a crazy question to ask, but I will do it 
anyway because we actually see a problem with this. Isnt it correct that 
two searches which only differs on the "rows"-number (documents to be 
returned) should always return the same value for "numFound"?

Thanks!

Regards, Steff