Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes? - Mailing list pgsql-hackers

Hi,

On 2023-02-12 19:59:00 +0530, Bharath Rupireddy wrote:
> Thanks for looking at it. We know that we don't change the zbuffer in
> the function, so can we avoid static const and have just a static
> variable, like the attached
> v1-0001-Use-static-variable-to-avoid-memset-calls-in-pg_p.patch? Do
> you see any problem with it?

Making it static const is better, because it allows the memory for the
variable to be put in a readonly section.


>      /* Prepare to write out a lot of copies of our zero buffer at once. */
>      for (i = 0; i < lengthof(iov); ++i)
>      {
> -        iov[i].iov_base = zbuffer.data;
> +        iov[i].iov_base = (void *) (unconstify(PGAlignedBlock *, &zbuffer)->data);
>          iov[i].iov_len = zbuffer_sz;
>      }

Another thing: I think we should either avoid iterating over all the IOVs if
we don't need them, or, even better, initialize the array as a constant, once.

Greetings,

Andres Freund