gistfile1.sql

WITH summary_groups as(
WITH summary as (
 select   (row_number() over (order by time asc nulls last)+1)/2 as rownum,time
  from     sensor_log_2013_10_27_12_01
  order by time asc)
  
SELECT
max(time) OVER(PARTITION BY rownum) - 
min(time) OVER(PARTITION BY rownum) diff
FROM summary)

SELECT 

avg(diff) as diffavg,

(SELECT max(time)-min(time) as total_diff FROM sensor_log_2013_10_27_12_01 as subq)/avg(diff) as num_steps

FROM summary_groups 
WHERE diff>0