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Find the N+1 Query Problem in Rails Apps in Under 5 Mins

AppMap Ruby
Open-source VSCode extension that creates interactive visualizations directly from Ruby apps. Made by the Architecture team at AppLand.
・1 min read

This video is based on the brilliant Eager Loading and the N+1 Query Problem blog post by Kevin Gilpin.

It is a short demonstration of how to identify the N+1 Query anti-pattern using the AppMap extension for VS Code, jq and the Rails Sample Application Sixth Edition as an example.

The N+1 anti-pattern happens when a query is executed for every result of a previous query. If left unchecked N+1 queries result in a gradual slowdown in the performance of an application.

N+1 Query Problem

Detecting  N+1 queries is tricky, because they are not revealed by any mainstream testing strategy.

To detect the N+1 query problems we need to look at the number of SQL queries that are performed in a realistic situation, such as an integration test, and compare this number with a “reasonable” expectation.

You can find full usage instructions, and all these links, on the AppMap page in the VSCode marketplace.

Thanks for watching!

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