Re: Direct I/O

On Sun, Apr 30, 2023 at 06:35:30PM +1200, Thomas Munro wrote:
> On Sun, Apr 30, 2023 at 4:11 PM Noah Misch <noah@leadboat.com> wrote:
> > Speaking of the developer-only status, I find the io_direct name more enticing
> > than force_parallel_mode, which PostgreSQL renamed due to overuse from people
> > expecting non-developer benefits.  Should this have a name starting with
> > debug_?
> 
> Hmm, yeah I think people coming from other databases would be tempted
> by it.  But, unlike the
> please-jam-a-gather-node-on-top-of-the-plan-so-I-can-debug-the-parallel-executor
> switch, I think of this thing more like an experimental feature that
> is just waiting for more features to make it useful.  What about a
> warning message about that at startup if it's on?

Such a warning wouldn't be particularly likely to be seen by someone who
already didn't read/understand the docs for the not-feature that they
turned on.

Since this is -currently- a developer-only feature, it seems reasonable
to rename the GUC to debug_direct_io, and (at such time as it's
considered to be helpful to users) later rename it to direct_io.  
That avoids the issue that random advice to enable direct_io=x under
v17+ is applied by people running v16.  +0.8 to do so.

Maybe in the future, it should be added to GUC_EXPLAIN, too ?

-- 
Justin