Findings about collation on PostgreSQL + Rails and its varying behaviors between OSs

rails-postgresql-development-on-macos.rb

# ==============================================================================
# On development's rails console (BSD based OS - MacOS):
# ------------------------------------------------------------------------------
a = %Q|SELECT * FROM json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","b":"bar"},{"a":"3","b":"FOO"},{"a":"4","b":"BOring"}]') AS x(a INT, b TEXT) ORDER BY b;|
ActiveRecord::Base.connection.execute(a).to_a
# [
#     [0] {
#         "a" => 4,
#         "b" => "BOring"
#     },
#     [1] {
#         "a" => 3,
#         "b" => "FOO"
#     },
#     [2] {
#         "a" => 2,
#         "b" => "bar"
#     },
#     [3] {
#         "a" => 1,
#         "b" => "foo"
#     }
# ]
b = %Q|SELECT * FROM json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","b":"bar"},{"a":"3","b":"FOO"},{"a":"4","b":"BOring"}]') AS x(a INT, b TEXT) ORDER BY b COLLATE "und-x-icu";|
ActiveRecord::Base.connection.execute(b).to_a
# [
#     [0] {
#         "a" => 2,
#         "b" => "bar"
#     },
#     [1] {
#         "a" => 4,
#         "b" => "BOring"
#     },
#     [2] {
#         "a" => 1,
#         "b" => "foo"
#     },
#     [3] {
#         "a" => 3,
#         "b" => "FOO"
#     }
# ]
# ==============================================================================

rails-postgresql-production-on-linux.rb

# ==============================================================================
# On productions's rails console (Linux based OS):
# ------------------------------------------------------------------------------
a = %Q|SELECT * FROM json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","b":"bar"},{"a":"3","b":"FOO"},{"a":"4","b":"BOring"}]') AS x(a INT, b TEXT) ORDER BY b;|
ActiveRecord::Base.connection.execute(a).to_a
# [
#     [0] {
#         "a" => 2,
#         "b" => "bar"
#     },
#     [1] {
#         "a" => 4,
#         "b" => "BOring"
#     },
#     [2] {
#         "a" => 1,
#         "b" => "foo"
#     },
#     [3] {
#         "a" => 3,
#         "b" => "FOO"
#     }
# ]
b = %Q|SELECT * FROM json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","b":"bar"},{"a":"3","b":"FOO"},{"a":"4","b":"BOring"}]') AS x(a INT, b TEXT) ORDER BY b COLLATE "und-x-icu";|
ActiveRecord::Base.connection.execute(b).to_a
# [
#     [0] {
#         "a" => 2,
#         "b" => "bar"
#     },
#     [1] {
#         "a" => 4,
#         "b" => "BOring"
#     },
#     [2] {
#         "a" => 1,
#         "b" => "foo"
#     },
#     [3] {
#         "a" => 3,
#         "b" => "FOO"
#     }
# ]
# ==============================================================================