So I'm curious. Why does order matter ?

Dave Cramer
www.postgres.rocks


When you have to save multiple new entities with subentities.

You first save all the parent entities in a single SQL batch insert, you get the generated ids, then insert all the subentities in another single SQL batch insert. To know which "parent id" to use for a given subentity of the second query, you need a way to associate a generated id with the correct parent entity. The order of the parents in their batch, and the order of the generated ids, is the only straighforward way.

I know all this could be made into a single SQL query, without having to associate the generated ids to the parents manually. But sometimes you have to fight /really /hard agains your framework or JDBC itself to write such more complex query, where two batch inserts are very natural.

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