SQL lab
Index vs sequential scan
Count the pages a sequential scan and a B-tree index lookup read to find one row.
The sequential scan reads every page even after it finds the row; the index scan reads one page per tree level plus a single heap page. On a bigger table the first number would grow with it, while the second would barely move.
Learn the concept
The lesson this lab comes from, with the explanation, a practice task and a quiz.
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