Query Processing and Optimization
Query Processing and Optimization
Query Processing and Optimization
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Comparison<br />
• Heuristic query optimization<br />
• Sequence of single query plans<br />
• Each plan is (presumably) more efficient than the previous.<br />
• Search is linear.<br />
• Cost-based query optimization<br />
• Many query plans generated.<br />
• The cost of each is estimated, with the most efficient chosen.<br />
• Search is multi-dimensional, usually using dynamic<br />
programming. Still can be very expensive.<br />
• Hybrid way<br />
• Systems may use heuristics to reduce the number of choices<br />
that must be made in a cost-based fashion.<br />
45
Change language