N-d Queries and Indexes
Generalised view of pmr and space queries:
select * from R
where a1 op1 C1 and ... and an opn Cn
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pmr : all opi are equality tests.
space : some opi are range tests.
Possible approaches to handling such queries ...
- use index on one ai to reduce tuple tests
- use indexes on all ai, and intersect answer sets
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