Extract Field transform displays "null"

Grafana Table Panel
1
  • What Grafana version and what operating system are you using?

v10.1.0

  • What are you trying to achieve?

https://play.grafana.org/d/aac76d76-3493-4f71-99ea-bfd09959b753/extract-field-transform-null-values-issue?orgId=1

I’m using the following data :

{"foo": "dude"}
{"bar": 125, "dude": null}

And using the Transform Data / Extract Field feature.

  • What happened?

Some cells not containing data are empty. Some display a “null” string.

Screenshot from 2023-11-29 16-46-51

  • What did you expect to happen?

I expect the cells not containing data to be empty. (or all of them to contain “null”).

2

What is the data source for this data

3

The data source doesn’t seem to be important. I tried first with a SQL query (PostgreSQL backend), but in the sandbox the data is Static.

4

Actually it is important as you could leverage functions in the querying language of the data source. here is an example in MS SQL

image

or

;with src
as
(
select '{"foo": "dude"}' as zaza union
select '{"bar": 125, "dude": null}'
)

SELECT *
from src
cross apply OPENJSON(src.zaza) WITH (
    foo NVARCHAR(50) '$.foo',
	bar INT '$.bar',
    dude  NVARCHAR(50)  '$.dude'
    );