Monty,

On Thu, Apr 16, 2020 at 3:32 PM Michael Widenius
<michael.widenius@gmail.com> wrote:
> > > ALTER PARTITION shadow files:
> > > #sql-shadow-'original_table_name'
> >
> > Please, add a thread_id here at the end. normally MDL should ensure that
> > no two threads can have a shadow for the same table at the same time,
> > but we have enough bugs as it is to introduce another vector when two
> > threads can overwrite each other temp files.
>
> That would make the file name even longer and I am not sure what
> happens if we table names goes much over
>  NAME_LEN.  I don't have time just now to check for possible name
> overruns (I think it should be save as most
> engines are using FN_REFLEN, but better safe than sorry.

FN_REFLEN limits the path name to only 511 or 512 bytes.
When I started using GNU/Linux in 1993, the maximum path name length
was 4095 or 4096 bytes. Already back then, extfs or xiafs or something
supported up to 255 bytes per path name component (name in a
directory).