BNLH algorithm always used a full table scan over the joined table
even in the cases when there existed range/index-merge scans that were cheaper than the full table scan. This was a defect/bug of the implementation of mwl #128. Now hash join can work not only with full table scan of the joined table, but also with full index scan, range and index-merge scans. Accordingly, in the cases when hash join is used the column 'type' in the EXPLAINs can contain now 'hash_ALL', 'hash_index', 'hash_range' and 'hash_index_merge'. If hash join is coupled with a range/index_merge scan then the columns 'key' and 'key_len' contain info not only on the used hash index, but also on the indexes used for the scan.
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