Anyone who has tried to build a small, realistic test database from a production schema knows the drill: you don't just want "all orders." You want a customer's orders, their order items, the products they reference — but not the entire payment history, not every audit log row, not the internal reporting tables three joins away. Every table you pull in for one reason drags in three more you didn't ask for, because your schema is a graph, not a list.Jailer solves the mechanical half of this problem: give it a starting table, a condition, and a set of rules for which relationships to follow, and it will walk the foreign-key graph and hand you back a consistent, referentially valid slice of the database. What it didn't solve, until recently, was the tedious half — sitting down and deciding, association by association, what to include and what to cut off. On a schema with a few hundred tables, that's not a five-minute job.