TL;DR InfluxDB Tech Tips - Timestamp Precision, Multiple Fields Function, Common Field Value

By Regan Kuchan / Developer
Aug 31, 2016

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In this post we recap the week’s most interesting InfluxDB and TICK-stack related issues, timestamp precision, multiple fields function, and common field value workarounds, how-tos and Q&A from GitHub, IRC and the InfluxDB Google Group that you might have missed.

Performance implications of timestamp precision

Q: I’m writing second-resolution data to InfluxDB using the HTTP API. Does it matter if I specify nanosecond precision timestamps with no precision query string parameter or second precision timestamps with the precision parameter?

So, is there any benefit to using one of the two following requests?

curl -i -XPOST "http://localhost:8086/write?db=weather" --data-binary 'temperature,location=1 value=90 1472666050000000000'

curl -i -XPOST "http://localhost:8086/write?db=weather&precision=s" --data-binary 'temperature,location=1 value=90 1472666050'

A: Yes. To maximize performance we recommend using the coarsest possible timestamp precision when writing data to InfluxDB. Specifying precision=s is the way to go!

Performing the same function on multiple fields

Q: I want to calculate the average for every field in a single measurement. Currently, I’m using the query below which takes a long time to write out. Is there a better way to do this?

> SELECT mean("alarm") AS "ave_alarm",mean("guests") AS "ave_guests",mean("temperature") AS "ave_temperature" FROM "home"
name: home
----------
time  ave_alarm  ave_guests  ave_temperature
0     0          1           70

A: Yes! Starting with version 1.0, aggregation functions support using an * to specify all fields in the measurement.

> SELECT mean(*) FROM "home"
name: home
----------
time  mean_alarm  mean_guests  mean_temperature
0     0           1            70

Finding the most common field value

Q: Is there a way to find the most common field value in a field?

A: Starting with version 1.0, InfluxDB supports the mode() function which finds the most frequent value in a field. Check out the functions page for more information.

For more InfluxDB tips, see our Frequently Asked Questionspage and feel free to post your questions in the InfluxDB users group.

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