See TableDefinition#column for details of the options you can use.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb, line 599
def column(column_name, type, index: nil, **options)
@base.add_column(name, column_name, type, **options)
if index
index_options = index.is_a?(Hash) ? index : {}
index(column_name, **index_options)
end
end