****** consider the following case
ls | count
17

ls | select name modified | count
17

ls | select name modified name | count. => duplicate name column here
34 => the count should still be 17 not 34

0 │ version │ 0.26.0
1 │ build_os │ macos-x86_64
2 │ rust_version │ rustc 1.49.0
3 │ cargo_version │ cargo 1.49.0
4 │ pkg_version │ 0.26.0
5 │ build_time │ 2021-01-27 21:21:53
6 │ build_rust_channel │ release
7 │ features │ ctrlc, default, directories, dirs, ichwh, ptree, rustyline, term, uuid, which, zip
───┴────────────────────┴────────────────────────────────────────────────────────────────────────────────────