On Sat, Aug 31, 2019 at 7:59 AM Robert Haas <robertmh...@gmail.com> wrote:
> On Thu, Aug 29, 2019 at 10:41 AM Jeevan Ladhe > <jeevan.la...@enterprisedb.com> wrote: > > Due to the inherent nature of pg_basebackup, the incremental backup also > > allows taking backup in tar and compressed format. But, pg_combinebackup > > does not understand how to restore this. I think we should either make > > pg_combinebackup support restoration of tar incremental backup or > restrict > > taking the incremental backup in tar format until pg_combinebackup > > supports the restoration by making option '--lsn' and '-Ft' exclusive. > > > > It is arguable that one can take the incremental backup in tar format, > extract > > that manually and then give the resultant directory as input to the > > pg_combinebackup, but I think that kills the purpose of having > > pg_combinebackup utility. > > I don't agree. You're right that you would have to untar (and > uncompress) the backup to run pg_combinebackup, but you would also > have to do that to restore a non-incremental backup, so it doesn't > seem much different. It's true that for an incremental backup you > might need to untar and uncompress multiple prior backups rather than > just one, but that's just the nature of an incremental backup. And, > on a practical level, if you want compression, which is pretty likely > if you're thinking about incremental backups, the way to get that is > to use tar format with -z or -Z. > > It might be interesting to teach pg_combinebackup to be able to read > tar-format backups, but I think that there are several variants of the > tar format, and I suspect it would need to read them all. If someone > un-tars and re-tars a backup with a different tar tool, we don't want > it to become unreadable. So we'd either have to write our own > de-tarring library or add an external dependency on one. Are we using any tar library in pg_basebackup.c? We already have the capability in pg_basebackup to do that. > I don't > think it's worth doing that at this point; I definitely don't think it > needs to be part of the first patch. > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company > > > -- Ibrar Ahmed
