derive_columns_hash_and_deduplicate_values

# File activerecord/lib/active_record/connection_adapters/schema_cache.rb, line 193
        def derive_columns_hash_and_deduplicate_values
          @columns      = deep_deduplicate(@columns)
          @columns_hash = @columns.transform_values { |columns| columns.index_by(&:name) }
          @primary_keys = deep_deduplicate(@primary_keys)
          @data_sources = deep_deduplicate(@data_sources)
          @indexes      = deep_deduplicate(@indexes)
        end