[lucw]

question: how does pgbackrest do incremental backup right now if postgres doesn't yet support it ?

[brand]

pgbackrest works purely at the file level, by looking at checksums. It’s rather primitive by comparison.

[aflukasz]

At filesystem level, yes, but worth noting that since v2.46 (from May 2023) it can also work with block level granularity: https://pgbackrest.org/configuration.html#section-repository...

[pilif]

By keeping the whole WAL.

The incremental backup would be just the WAL segments excluding the base backup.

With this new feature, the WAL segments you need to store are much, much smaller.

[aflukasz]

> By keeping the whole WAL.

Not exactly. Pgbackrest can do incremental backups that are restored by applying file system level diffs (stored in incremental backup) to the base backup. WALs are only involved at the very last step when restore process is finalized by applying WALs that were generated during BACKUP step itself. But that's not pgbackrest limitation, that's how any Postgres restore process works.

EDIT: "how any Postgres restore process works" that restore a backup done from a live database that is being written to when backup is taking place.