Probably related to bug 32932.

On Fri, 2 Nov 2018, 14:08 Filipp Gunbin <fgunbin@fastmail.fm wrote:

> emacs -Q
> M-x sql-postgres, enter connection details.
> Type RET until prompt is at the window bottom.
> Type something invalid as a command, like 'asdf', then RET.  Prompt
> changes to '->'.
> Type semicolon, then RET.
>
> The resulting output is in the attached screenshot.  The line with '6'
> was the mode line, which got erased.
>
> I've checked that it's not related to the patch in bug 33154 which I'm
> currently testing.
>
> Thanks.
>
> In GNU Emacs 27.0.50 (build 3, x86_64-apple-darwin17.7.0, NS
> appkit-1561.60 Version 10.13.6 (Build 17G65))
>  of 2018-11-02 built on fgunbin.playteam.ru
> Repository revision: 5b218be0c362316384f5c9ef57a3bef02f742e94
> System Description:  Mac OS X 10.13.6
>
>