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Just run the whole operation in a transaction and verify whatever you need to verify before committing.

BEGIN TRANSACTION;

... ; Modify DB

... ; Inspect State

ROLLBACK TRANSACTION;

and then switch the rollback to commit when satisfied

This is cool I probably will do this.

Just mind the isolation level of concurrent queries which may be running. By default you are probably fine since it's usually snapshot isolation mode (will only see committed results as of query start) but there are other modes that break this.

maybe you could run the updates in a transaction that you could roll back if you were unhappy with the result?