In this post we recap the week’s most interesting InfluxDB and TICK-stack related issues, workarounds, how-to return readable Timestamps in the CLI and Q&A from GitHub, IRC and the InfluxDB Google Group that you might have missed.
Question: How do you make InfluxDB’s CLI return human readable timestamps?
Instead of this:
name: clothes --------- time percent_cool 892482496000000000 0.5 Return this: name: clothes --------- time percent_cool 1998-04-13T15:48:16Z 0.5
Answer: When you first connect to the CLI, specify the rfc3339 precision:
$ influx -precision rfc3339
Alternatively, specify the precision once you’ve already connected to the CLI:
$ influx Connected to http://localhost:8086 version 0.xx.x InfluxDB shell 0.xx.x > precision rfc3339 >
Check out our docs for more useful CLI options.
Question: How do you calculate the average of the difference between two fields? This query returns an error:
> SELECT mean(field1 - field2) from my_measurement
Answer: Currently, InfluxQL can’t do this in one query. We recommend first, calculating the difference and writing the results to a new field and second, calculating the average of that new field.
# Write some data > INSERT pet_daycare cats=5,dogs=7 > INSERT pet_daycare cats=6,dogs=9 > SELECT * FROM pet_daycare name: pet_daycare ----------------- time cats dogs 2016-04-13T16:10:19.237337894Z 5 7 2016-04-13T16:10:25.844917838Z 6 9 # Calculate the difference and write the results to the same measurement using INTO > SELECT dogs - cats INTO pet_daycare FROM pet_daycare name: result ------------ time written 1970-01-01T00:00:00Z 2 > SELECT * FROM pet_daycare name: pet_daycare ----------------- time cats dogs dogs_cats 2016-04-13T16:10:19.237337894Z 5 7 2 2016-04-13T16:10:25.844917838Z 6 9 3 # Calculate the average of the new field > SELECT mean(dogs_cats) FROM pet_daycare name: pet_daycare ----------------- time mean 1970-01-01T00:00:00Z 2.5
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