How wide a block's min–max range is

How it behaves

One input on the horizontal axis, the others held fixed.

Worked examples, recomputed

Every number the mechanisms quote for this relationship is recomputed from it, so none of them disagrees with it.

• b = 10⁶ rows → 0.999998 of the domain
• B = 10,000 → 99.98% of the domain

Where it appears

Each mechanism states it in its own names. The general symbol each name stands for is shown with it.

• Indexing

  When does a separate "where is it?" structure pay for itself, and what does it cost to keep it true?

  $$(b-1)/(b+1)$$

  Read it in place →

• Query Planning & Optimization

  How does a system choose a plan for a question when the facts that decide the best plan are unknown until the plan has run?

  $$(B-1)/(B+1)$$

  B (rows per block) = $b$

  Read it in place →