for example, having this class:

class MyDocument
include Mongoid::Document
field :one_field, type: String
field :another_field, type: String

index(

{one_field: 1, another_field: 1}

)
index(

{another_field: 1, one_field: 1}

)
end

will only create one index, this is because index_options is a hash that uses index() first parameter as key, so the second call to index() would update the same object.

this is fixable by doing

class MyDocument
include Mongoid::Document
field :one_field, type: String
field :another_field, type: String

index_options.compare_by_identity
index(

{one_field: 1, another_field: 1}

)
index(

{another_field: 1, one_field: 1}

)
end

that makes the index_option hash recognize both keys as different, maybe this should be enabled by default?