Settings
Everything here is stored in this browser. There is no account to attach it to, and nothing leaves the page unless you switch on sync below — until then the export button is the only backup that exists.
Appearance
Theme
System follows your operating system while the tab is open. The palette is defined twice — once for each theme — and never generated from the other.
Engine
Dataset scale
Small is a hundred or so rows, sized for reading a result set. Realistic is a million, generated lazily from a seed, and it is the only size where a cost mistake actually hurts.
Explain every query
Runs EXPLAIN alongside each playground query without being asked. Off by default in drills, where reaching for the plan yourself is part of what is being measured.
Editor
Font size
The query editor only. Lesson prose has its own scale and does not follow this.
Line numbers
Parse errors are reported with a line and column, so the numbers are worth having when a query grows past a few lines.
The planner
The cost model’s constants. These are a model, not milliseconds — they do not predict your production database. What they are good for is comparison, and turning one changes every plan in the app at once.
random_page_cost
What a page fetched at random costs against one read in sequence. The default of 4 describes a spinning disk; on an SSD it is closer to 1, and almost nobody changes it. Set it to 1 and watch the index scans appear.
work_mem
How much a sort or a hash may hold before it has to batch. Lower it and watch a hash join report more batches and a sort start paying for pages.
Your data
- Exercises
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- Solved
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- Attempts
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- Stored
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This browser is not storing anything. The session works, but nothing will survive the tab.
Reset learning progress
Clears lessons, attempts and history. Your notes, revisit flags and ratings are kept.
Delete all local data
Everything, including your notes and anything you have saved. There is no server copy, so this cannot be undone.
Sync
Sync to your own server
OffOff. Everything stays in this browser. Turn this on and SQL keeps a copy on a storage server you run, so a second machine sees the same history. There is still no account — the API key is the only identity, and losing it loses the copy.
Each gym is a separate site, so this setting only covers SQL. The other gyms take the same endpoint and the same key.
Run your own server The wire protocol is written down — small enough that writing one is an afternoon, and the page doubles as a prompt you can hand to a coding agent.liter8.sh/remote-storage