source: simon willison: sqlite query explainer
level: technical
simon willison built a tool that lets you run sql queries against a sqlite database directly in your browser. it uses pyodide to run python and sqlite in webassembly, so no server is needed. after you enter a query, the tool shows both the high-level explain query plan and the low-level bytecode explain output. each line gets a plain english annotation describing what the query planner or virtual machine is doing.
the idea came from julia evans, who mentioned wanting to learn how to read a query plan. willison used fable, an ai coding tool, to help build the interactive explainer. he warns that he cannot fully verify the explanations himself, since he is not an expert on sqlite internals, but the output looks reasonable. the tool is meant to help developers understand how sqlite processes their queries step by step.
the tool is open for anyone to try. it runs entirely in the browser, so your data stays local. you can type any sql statement and immediately see the execution plan. this makes it easier to debug slow queries or learn how sqlite optimizes joins, indexes, and filters. the annotations translate technical plan output into something closer to human language.
why it matters: understanding query plans helps data scientists and developers write faster sql and debug performance issues without needing deep database internals knowledge.