RE: Disable WAL logging to speed up data loading

Hello, Sawada-San

On Friday, November 27, 2020 3:08 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> - (errmsg("WAL was generated with wal_level=minimal,
> data may be missing"),
> + (errmsg("WAL was generated with wal_level<=minimal,
> data may be missing"),
> errhint("This happens if you temporarily set
> wal_level=minimal without taking a new base backup.")));
>
> 'wal_level=minimal' in errhint also needs to be changed to
> 'wal_level<=minimal'?
Yeah, thanks. I'll fix this point in the next patch.

> While testing the patch on some workload, I realized that
> XLOG_FPI_FOR_HINT record could still be emitted even when wal_level =
> none. IIUC that WAL record is not necessary during wal_level = none since
> the server cannot be the primary server and the server crash ends up requiring
> to restore the whole database.
That's right. Yeah, I'm aware of the fact that
we can refine the types of WAL. Basically, I thought the amount of
WALs related to XLOG and XACT should be less than that of other types and
generating those doesn't have a serious impact on the peformance.
But anyway, thanks for your advice !

Best,
Takamichi Osumi