# Pull request reviewer Snoutbot reviews the database change in a pull request **against the database that change is going to land on**. That is the whole idea. Any linter can read a migration and tell you it looks destructive. Snoutbot connects to the destination, asks it read-only questions, and tells you what is actually true there: > **This will fail: 412 rows in `orders` are NULL** > > A NOT NULL constraint is rejected while any row already violates it, so the migration stops at > this statement. Backfill the column in its own migration first, then add the constraint once > nothing is NULL. > > *Measured: 412 rows with a NULL in that column, on Snout, 2026-08-31 22:22 UTC.* Whether `ALTER TABLE orders MODIFY ship_date DATE NOT NULL` succeeds is not a property of the SQL. It is a property of the rows, and the rows are not in the diff. ## Where it runs Inside SnoutData, on your machine, over the database connections you have already set up. There is no server of ours in the path: - Your database credentials stay in your OS keychain and are used locally. - Your repository token is yours, and the comment is posted by your own account. - Nothing about your schema, your data or your diff reaches us. This is the reason it is a desktop feature. A cloud reviewer that checks your production database needs access to your production database, and most teams are right to refuse that. ## What it costs Nothing by default, and no model is called. The findings are produced by a deterministic rule set: it either measured 412 NULLs or it did not. If you want written explanations underneath the findings, you choose who writes them. See [Where your data goes](https://docs.snoutdata.com/reviewer/privacy.md). ## Next - [Set it up](https://docs.snoutdata.com/reviewer/setup.md) - connect a host, watch a repository, bind a connection. - [How it reviews](https://docs.snoutdata.com/reviewer/how-it-reviews.md) - the three depths, and what each one can know. - [Where your data goes](https://docs.snoutdata.com/reviewer/privacy.md) - the four ways to review, and the boundary of each.