On Wed, Jul 19, 2017 at 8:56 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wonder if it'd be worth the trouble to stick something like this into
> xlog.c:
>
> /*
> * For reliability's sake, it's critical that pg_control updates
> * be atomic writes. That generally means the active data can't
> * be more than one disk sector, which is 512 bytes on common
> * hardware. Be very careful about raising this limit.
> */
> StaticAssertStmt(sizeof(ControlFileData) <= 512,
> "pg_control is too large for atomic disk writes");
+1. Even if it just gets triggered in 20 years by some hacker, that's
a good reminder about assumptions behind the update logic.
--
Michael