Result Size Estimation (cont’d)

• Selections:

  • Use reduction factors, logic, probability
  • Often use histograms, other statistics

• Projections:

  • Ignore duplicate elimination (done last, if needed)
  • Tuple size is reduced ? fewer pages for result

• Joins: like selections, plus:

  • Use candidate key information
  • Should consider “dangling” tuples

Previous slide

Next slide

Back to first slide

View graphic version