If we land this patch, NLJ will no longer be pushed down to SBE.
This is when no index can be used on the foreign side and the foreign side is too big to use a hash join.

Description of Linked Ticket

This task should check the index catalog for a wildcard, sparse, partial (possibly other special) indexes against the foreign collection that cover the join field, and if such an index exists we need to fall-back to the classic engine. 

The main reason is these special indexes aren't supported by sbe currently, and we would replace an ix_scan with a collscan and incur a perf hit.