When updatedb is spawned by cron it prunes all "API" filesystems, i.e. filesystems which have no backing device, thus are marked as nodev in /proc/filesystems. ZFS on Linux is also marked nodev despite the fact it is filesystem used to actually store the data.
ZFS volumes are not indexed.
Exception for ZFS was added to cron script thus when updatedb is spawned it will also index ZFS filesystems.
It is possible to search with locate for files stored on ZFS filesystems.