Postings Format for Span queries on big index

[Gopal Agarwal <go...@gmail.com>]

Does lucene 4.6 use Lucene41PostingsFormat for Postings.nextdoc() while
executing the span queries?

When I am debugging the lucene 4.6 test cases for span queries, it is
showing that for above nextdoc() call it is utilizing DirectPostingsFormat.

My requirement is to run multiple span queries like "cat dog"~2 on 2 TB of
index and I am worried about the performance as I have to collect all the
docs in results.

For better performance:
Is there a better postingsformat to choose from while using span queries in
solr 4.6 or solr4.7? Given that we have lot of formats to choose from.

Does having termVectors=true or termPositions=true and termOffsets=true
helps?
If yes then, should I think about what to use as TermVectorFormat?

Thanks,
Gopal