index_column_diff: improve remained time
index_column_diff: improve remained time

komainu8/groonga,komainu8/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,naoa/groonga,groonga/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,komainu8/groonga,groonga/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,naoa/groonga,groonga/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,komainu8/groonga,komainu8/groonga,komainu8/groonga,komainu8/groonga,naoa/groonga,naoa/groonga,kenhys/groonga