Some session data on Redis have 64-byte key name, not 32-byte

Found that some session data on Redis have 64-byte key name, not 32-byte in our GitLab setup (omnibus-gitlab 8.8.5 continuously upgraded from 7.1.x) as confirmed in the following way:

$ rcli keys '*' | grep '^session:gitlab:' | wc -l
206878
$ rcli keys '*' | grep '^session:gitlab:' | awk -F : '{ print length($3) }' | sort | uniq -c
 206871 32
      7 64
$ rcli keys '*' | grep '^session:gitlab:[a-f0-9]\{64\}$'
session:gitlab:2d47e6187a017039a43284c4e96ba1d71e944766ae7bd839735b71ef2b39ae73
session:gitlab:ab090362df7662a5925ba63efb326208851b0d8cfca0334d8ca1e3ee7a63e198
session:gitlab:9c0da4085a3684ac5a1afd6bca5a97c76dae2f8307c235fe818c5e445d6dc6ff
session:gitlab:e5bf88442627da573ead598ea31ce5affc5d5a738852ec021d08e585557e2c42
session:gitlab:1554795996799924bb755f106320be9baaba8b2e83a37b4a5e739431aa1ae00d
session:gitlab:95c35030e16ca2889349fe630a637217b1ae3c6409c814eca19d0874c8e74292
session:gitlab:b4894330a24ac817eab34112db3f7eca19f3829f663b4ed95ec33777243d4871

rcli comes from the docs.

I can’t imaging why we have 64-byte session keys. Anyone knows the reason and if we should remove these “illegal” sessions?