The restore command is implemented entirely in C.

For the most part this is a direct migration of the Perl code into C.

There is one important behavioral change with regard to how file permissions are handled.  The Perl code tried to set ownership as it was in the manifest even when running as an unprivileged user.  This usually just led to errors and frustration.

The C code works like this:

If a restore is run as a non-root user (the typical scenario) then all files restored will belong to the user/group executing pgBackRest. If existing files are not owned by the executing user/group then an error will result if the ownership cannot be updated to the executing user/group. In that case the file ownership will need to be updated by a privileged user before the restore can be retried.

If a restore is run as the root user then pgBackRest will attempt to recreate the ownership recorded in the manifest when the backup was made. Only user/group names are stored in the manifest so the same names must exist on the restore host for this to work. If the user/group name cannot be found locally then the user/group of the PostgreSQL data directory will be used and finally root if the data directory user/group cannot be mapped to a name.

Reviewed by Cynthia Shang.

src/postgres/version.h

@@ -38,6 +38,15 @@ Version where various PostgreSQL capabilities were introduced
 // pg_create_restore_point() supported
 #define PG_VERSION_RESTORE_POINT                                    PG_VERSION_91
 
+// pause_at_recovery_target is supported
+#define PG_VERSION_RECOVERY_TARGET_PAUSE                            PG_VERSION_91
+
+// tablespace_map is created during backup
+#define PG_VERSION_TABLESPACE_MAP                                   PG_VERSION_95
+
+// recovery target action supported
+#define PG_VERSION_RECOVERY_TARGET_ACTION                           PG_VERSION_95
+
 // xlog was renamed to wal
 #define PG_VERSION_WAL_RENAME                                       PG_VERSION_10