Matthew Woodcraft <matthew@xxxxxxxxxxxxxxx> writes: > In an INSERT, are the rows guaranteed to be inserted in the order that > the source query returns its rows, for locking purposes? I dunno that we "guarantee" that, but it's hard to see why the code would behave any differently, at present. > and I run two concurrent copies of > INSERT INTO foo (SELECT n FROM ... ORDER BY n); > is there any guarantee that I'll get a unique constraint violation > rather than a deadlock? Well, the issue there is not about the physical insertion order but the order in which the uniqueness checks happen. I think you'd be all right with a traditional-style PG index, but maybe not with a deferrable unique constraint. regards, tom lane
