SciTools/iris — pull request #587 by cpelley (2013-07-01 12:20:12+00:00)
Title: MAINT: Optimise constructing ordered metadata

Currently cell objects comparisons are made which have much greater
expense to native python datatypes (tuples) when thousands of 'fields'
are concerned. This commit switches to using standard tuples, resulting
in 50% gains in speed over the code segment.