TL;DR InfluxDB Tech Tips - Query vs Writing Booleans & Checking Field Types
Regan Kuchan /
Jun 01, 2016
In this post we recap the week’s most interesting InfluxDB and TICK-stack related issues, workarounds, how-tos with writing booleans and Q&A from GitHub, IRC and the InfluxDB Google Group that you might have missed.
Querying data in a non-DEFAULT retention policy
Q: I created a new retention policy called
secret_garden. I started writing data to that retention policy and the logs show that the writes are successful, but when I query the data I get an empty response. What am I doing wrong?
Results of the
SHOW RETENTION POLICIES query:
> SHOW RETENTION POLICIES ON "lands" name duration shardGroupDuration replicaN DEFAULT default 0 168h0m0s 1 true secret_garden 24h0m0s 1h0m0s 1 false
Results of a
> SELECT * FROM "foliage" >
A: The retention policy
secret_garden is not the
DEFAULT retention policy for your database (see the fifth column in the
SHOW RETENTION POLICIES output).
You’ll need to fully qualify the measurement
foliage if you’re querying data in a retention policy that is not the
DEFAULT retention policy. Fully qualify a measurement by specifying the database and retention policy in the
> SELECT * FROM "lands"."secret_garden"."foliage" name: foliage ------------- time roses 2016-05-31T17:09:04.697144667Z 3 2016-05-31T17:09:07.096708707Z 5
Checking field types
Q: Is there a way to see a field’s data type?
A: Starting with InfluxDB version 1.0, the
SHOW FIELD KEYS query also returns the field type.
> SHOW FIELD KEYS FROM all_the_types name: all_the_types ------------------- fieldKey fieldType blue string green boolean orange integer yellow float
Querying vs. writing booleans
Q: I’m able to successfully write booleans to my database, but I can’t seem to use them in my query’s
> INSERT hamlet tobe=t > INSERT hamlet tobe=f > SELECT * FROM "hamlet" WHERE "tobe"=t >
A: Acceptable boolean syntax differs for writes and for queries.
In your case, InfluxDB understands that
t means true when you write your data but it doesn’t understand that
t means true when you query your data. You’ll need to use
TRUE to reference that boolean value in a query.
> SELECT * FROM "hamlet" WHERE "tobe"=true name: hamlet ------------ time tobe 2016-05-31T18:07:32.93151244Z true
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