Migrations should run SQL statements sequentially, not all together.

It's difficult to debug migrations because the SQL for an entire file is concatenated into one piece before execution. The error report is on the entire glob of statements, rather than a particular statement, and generally doesn't say anything helpful. I doubt there is any significant speed increase to be had on *migrations* by executing all statements as one.

Start by locating the migration execution path that concatenates the SQL for an entire file before running it. Change the behavior so statements run sequentially, then verify that failures identify an individual statement and that the migration behavior remains correct.

Written by the indexing model from the issue text.