Continuous Query

• Looking at the sample data - we have a lot of individual measure points:

  h2o_feet,location=coyote_creek water_level=8.120,level\ description="between 6 and 9 feet" 1439856000
  h2o_feet,location=coyote_creek water_level=8.005,level\ description="between 6 and 9 feet" 1439856360
  h2o_feet,location=coyote_creek water_level=7.887,level\ description="between 6 and 9 feet" 1439856720
  h2o_feet,location=coyote_creek water_level=7.762,level\ description="between 6 and 9 feet" 1439857080
  h2o_feet,location=coyote_creek water_level=7.635,level\ description="between 6 and 9 feet" 1439857440
  h2o_feet,location=coyote_creek water_level=7.500,level\ description="between 6 and 9 feet" 1439857800
  

• Basic CQ syntax (multi-lines in cli are not supported):

  CREATE CONTINUOUS QUERY <cq_name> ON <database_name>
  BEGIN
  SELECT <function[s]> INTO <destination_measurement> FROM <measurement> [WHERE <criteria>] GROUP BY time(<interval>)[,<tag_key[s]>]
  END
  

• Example of CQ for NOAA data (eliminate line breaks!):

  CREATE CONTINUOUS QUERY "cq-h2o-feet-daily" ON "NOAA_water_database"
  BEGIN
  SELECT mean("water_level") INTO "h2o-feet-daily" FROM "h2o_feet" GROUP BY time(1d)
  END
  

• CQ requires a function, an INTO clause, and a GROUP BY time() clause
• function: count(), distinct(), max(), top() and quite a few more
• INTO: name of the measurement to write results into
• GROUP BY time(): timestamp interval e.g.: 12m or 1d, more duration literals
• Common issues with basic syntax