Re: Duplicate key error when updating unique columns

Michael Glaesemann  writes:
> I thought that the unique key would be checked at the end of the update  
> statement:

No, it's never worked that way.  Each row is checked as it is inserted.
With an example like this, you may or may not get a failure depending on
chance physical ordering of rows.

This is not per spec, and I believe we have a TODO to fix it, but a fix
is far from trivial.

			regards, tom lane