Ecto - Postgresql wiki: Don't do this

[OvermindDL1]

@cnck1387

If you use varchar(N) , what happens if you change N down the line? How would pg know to modify the underlying constraint’s length?

Don’t quote me, but as I recall it sets the new constraint and wipes the old one atomically (and linearly, I.E. it can take time), and depending on set option it will either truncate or error at that time if anything is too long then.