--- title: Things you didn't know about indexes | daily.dev description: A practical guide to database indexing covering both fundamentals and common pitfalls. Explains how indexes work (B-tree structure, binary search), the... canonical: https://daily.dev/posts/things-you-didn-t-know-about-indexes-a4znm2ugw twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Things you didn't know about indexes | daily.dev og:description: A practical guide to database indexing covering both fundamentals and common pitfalls. Explains how indexes work (B-tree structure, binary search), the... og:url: https://daily.dev/posts/things-you-didn-t-know-about-indexes-a4znm2ugw og:image: https://api.daily.dev/og/posts/a4Znm2UGW.png og:image:alt: Things you didn't know about indexes og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Things you didn't know about indexes **[Lobsters](https://daily.dev/sources/lobsters)** · 12 min read · 0 upvotes · 0 comments ## Summary A practical guide to database indexing covering both fundamentals and common pitfalls. Explains how indexes work (B-tree structure, binary search), the read-fast/write-slow trade-off, and storage costs. Covers four key gotchas and index types: composite index column ordering (left-prefix rule), function-wrapped columns breaking index usage, functional/expression indexes, partial indexes for low-cardinality or filtered data, and covering indexes (Index Only Scan) using PostgreSQL's INCLUDE clause. Uses a Pokémon table as a running example throughout, with EXPLAIN and EXPLAIN ANALYZE shown as diagnostic tools. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [How Database Indexes Work – A Practical Guide with PostgreSQL Examples](https://daily.dev/posts/how-database-indexes-work-a-practical-guide-with-postgresql-examples-8anfbdgcl) · freeCodeCamp · 72 upvotes · 0 comments - [Introduction to PostgreSQL Indexes ::](https://daily.dev/posts/introduction-to-postgresql-indexes--peasixbnz) · Hacker News · 0 upvotes · 0 comments - [SQL Indexing Explained: Composite Indexes and Column Order](https://daily.dev/posts/sql-indexing-explained-composite-indexes-and-column-order-exxme3lqv) · Milan Jovanović · 42 upvotes · 1 comments - [Beyond Indexes: How Open Table Formats Optimize Query Performance — Jack Vanlightly](https://daily.dev/posts/beyond-indexes-how-open-table-formats-optimize-query-performance-jack-vanlightly-inrhgb2yf) · Programming Digest · 0 upvotes · 0 comments --- Tags: [#backend](https://daily.dev/tags/backend), [#postgresql](https://daily.dev/tags/postgresql) [View this post on daily.dev](https://daily.dev/posts/things-you-didn-t-know-about-indexes-a4znm2ugw) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Things you didn't know about indexes","url":"https://daily.dev/posts/things-you-didn-t-know-about-indexes-a4znm2ugw","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/things-you-didn-t-know-about-indexes-a4znm2ugw"},"datePublished":"2026-04-15T17:54:08.444Z","dateModified":"2026-04-16T17:54:34.875Z","description":"A practical guide to database indexing covering both fundamentals and common pitfalls. 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