Re: Different compression methods for FPI

On Wed, Sep 07, 2022 at 03:29:08PM +0900, Michael Paquier wrote:
> At the end, I have not taken the approach to use errdetail() for this
> problem as errormsg_buf is designed to include an error string. So, I
> have finished by refining the error messages generated in
> RestoreBlockImage(), consuming them with an ERRCODE_INTERNAL_ERROR.

The cases involving max_block_id, has_image and in_use are still "can't
happen" cases, which used to hit elog(), and INTERNAL_ERROR sounds right
for them.

But that's also what'll happen when attempting to replay WAL using a postgres
build which doesn't support the necessary compression method. I ran into this
while compiling postgres locally while reporting the recovery_prefetch bug,
when I failed to compile --with-zstd. Note that basebackup does:

src/backend/backup/basebackup_zstd.c- ereport(ERROR,
src/backend/backup/basebackup_zstd.c- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
src/backend/backup/basebackup_zstd.c: errmsg("zstd compression is not supported by this build")));
src/backend/backup/basebackup_zstd.c- return NULL; /* keep compiler quiet */

--
Justin