Free Indexes, queries and scale lessonsIndexes, queries and scale · Stage 0 · Where the data lives · Step 1
Rows, pages and the cost of a scan
See how rows are packed into fixed-size pages, why the page is the unit of cost, and how to estimate a full scan. About 12 minutes.
A table has 10 million 200-byte rows on 8,192-byte pages. About how many pages is it?
- AAbout 250,000
- BAbout 10 million
- CAbout 25,000
Show the answer
About 250,000. 40 rows per page, so 10,000,000 / 40 = 250,000 pages.
4 questions on this idea
Short questions that apply the idea to new cases: trace it, work out a number, put steps in order. A wrong answer explains itself.
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