Sort-merge-join: an idea whose time has(h) passed?

Matching two sets of data items is a fundamental operation required in relational, extensible, and object-oriented database systems alike. However, the pros and cons of sort- and hash-based query evaluation techniques in modern query processing systems are still not fully understood. After our earlier research clarified strengths and weaknesses of sort- and hash-based query processing techniques and suggested remedies for the shortcomings of hash-based algorithms, the present paper outlines a number of further differences between sort-merge-join and hybrid hash join that traditionally have been ignored in such comparisons and render sort-merge-join mostly obsolete. We consolidate old and raise new issues pertinent to the comparison of sort- and hash-based query evaluation techniques and stir some thought and discussion among both academic and industrial database system builders.<>