Debug Toolbarによるプロファイリング

The Django Debug Toolbar shows exactly how many queries a page runs, so you optimize with facts instead of hunches. 🔍

You add it with pip, just like any package. It is a development tool, so it never ships to production.

Add it to INSTALLED_APPS so Django loads its panels and knows the toolbar exists.

Its middleware injects the panel into HTML responses, so it sits near the top of your middleware list.

The toolbar only appears for IPs in INTERNAL_IPS, which keeps it visible to you but hidden from real visitors.

The star panel is SQL. It lists every query a page ran, with its timing, right beside the rendered output.

A surprisingly high query count is the classic fingerprint of N+1. The toolbar makes that number impossible to miss.

It even flags duplicate queries, the near-identical ones a loop fires over and over, pointing straight at the problem.

After adding select_related or prefetch_related, reload and watch the count drop. That is your proof the fix worked.

Slow pages are not always about count. The toolbar shows time per query, so you can chase the truly expensive ones.

Wrap toolbar settings behind your DEBUG flag. It can leak internals and slow pages, so production must never see it.

One last check on profiling habits.

The Debug Toolbar counts and times queries so you can spot N+1 and confirm fixes. Install it, allow your IP, and keep it dev-only. ✅