Re: Direct I/O

On Sun, Apr 30, 2023 at 6:35 PM Thomas Munro  wrote:
> On Sun, Apr 30, 2023 at 4:11 PM Noah Misch  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?

Something like this?  Better words welcome.

$ ~/install//bin/postgres -D pgdata -c io_direct=data
2023-05-01 09:44:37.460 NZST [99675] LOG:  starting PostgreSQL 16devel
on x86_64-unknown-freebsd13.2, compiled by FreeBSD clang version
14.0.5 (https://github.com/llvm/llvm-project.git
llvmorg-14.0.5-0-gc12386ae247c), 64-bit
2023-05-01 09:44:37.460 NZST [99675] LOG:  listening on IPv6 address
"::1", port 5432
2023-05-01 09:44:37.460 NZST [99675] LOG:  listening on IPv4 address
"127.0.0.1", port 5432
2023-05-01 09:44:37.461 NZST [99675] LOG:  listening on Unix socket
"/tmp/.s.PGSQL.5432"
2023-05-01 09:44:37.463 NZST [99675] WARNING:  io_direct is an
experimental setting for developer testing only
2023-05-01 09:44:37.463 NZST [99675] HINT:  File I/O may be
inefficient or not work on some file systems.
2023-05-01 09:44:37.465 NZST [99678] LOG:  database system was shut
down at 2023-05-01 09:43:51 NZST
2023-05-01 09:44:37.468 NZST [99675] LOG:  database system is ready to
accept connections