Database Management Systems · Storage and query processing

Indexes and B-trees

A sorted, tree-shaped shortcut structure that lets the database find rows without scanning the whole table.

Also known as: B+ trees, index structures.

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Learn first

• Storage and file organization: How rows actually get laid out into pages and files on disk.

Leads to

• Index selectivity: How narrowly a condition filters the table, the reason a low-selectivity index gets ignored in favor of a full scan.
• Query processing and optimization: How the database decides which order to run joins and filters in, to answer a query as cheaply as possible.
• Database administration and performance tuning: The ongoing work of keeping a database backed up, monitored, and fast as real usage grows.

Related topics

• Index selectivity: How narrowly a condition filters the table, the reason a low-selectivity index gets ignored in favor of a full scan.
• Query processing and optimization: How the database decides which order to run joins and filters in, to answer a query as cheaply as possible.