Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Some time ago, the tab completion code for the SET command was changed
> to read the list of available settings from the pg_settings table.
> This means that by the time you're done completing SET TRANSACTION
> ISOLATION, you've already sent a query and the command will be
> disallowed.
Of course, there's always Plan B: revert that patch and go back to
a hard-coded list of variable names.
regards, tom lane