Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?

On Tue, Sep 27, 2022 at 6:43 PM Bharath Rupireddy
<bharath.rupireddyforpostgres@gmail.com> wrote:
> On Tue, Sep 27, 2022 at 3:08 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> >
> > I don't think so, that's an extra kernel call.  I think I'll just have
> > to revert part of my recent change that removed the pg_ prefix from
> > those function names in our code, and restore the comment that warns
> > you about the portability hazard (I thought it went away with HP-UX
> > 10, where we were literally calling lseek() before every write()).
> > The majority of users of these functions don't intermix them with
> > calls to read()/write(), so they don't care about the file position,
> > so I think it's just something we'll have to continue to be mindful of
> > in the places that do.
>
> Yes, all of the existing pwrite() callers don't care about the file
> position, but the new callers such as the actual idea and patch
> proposed here in this thread cares.
>
> Is this the commit cf112c122060568aa06efe4e6e6fb9b2dd4f1090 part of
> which [1] you're planning to revert?

Yeah, just the renaming parts of that.  The lseek()-based emulation is
definitely not coming back.  Something like the attached.