Grafana refuses to plot some variables

Grafana PostgreSQL
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1

  • grafana 5-latest, ubuntu 21.10, self hosted

  • What are you trying to achieve?
    I want to have a line plot for each day of the number of new cases, hospitalizations and deaths due to covid-19.

  • How are you trying to achieve it?
    I have downloaded the covid-19 figures of out world in data. From that I created a postgres database with a little over 161,000 rows and about 67 variables. There are observations for each day of several variables for most countries. Currently I try to plot the figures for the Netherlands (iso_code=‘NLD’).

This works for SELECT date as “time”, new_cases but not for when I replace new_cases by new_cases_per_million.

  • What happened?
    When I select the column new_cases_per_million the selection “jumps back” to new_cases, the graph does not change. The user interface refuses to select the column. This happens to a lot of variables. In postgres this column contains values, a number of each day. When I try to force a graph of new_cases_per_million by editing the SQL like:

SELECT
  date AS "time",
  new_cases_per_million
FROM dapp_dataobservation
WHERE
  iso_code = 'NLD'
ORDER BY 1

Still no graph is shown and when I switch back to the query builder it shows new_cases again.

  • What did you expect to happen?
    When I select new_cases_per_million I expect to see variable new_cases_per_millon in the SELECT section of the query builder and a graph that show the numbers.

  • Can you copy/paste the configuration(s) that you are having problems with?
    I am prepared to do that but couldn’t find information how to do that.

  • Did you receive any errors in the Grafana UI or in related logs? If so, please tell us exactly what they were.
    /var/log/grafana/grafana.log showed some initial errors of the moment I provided the wrong credentials to the postgres source. After correcting this there are no errors to be found.

  • Did you follow any online instructions? If so, what is the URL?
    No

2

What datatype has new_cases_per_million column in the DB?

3

Data type is ‘Double precision’.

4

Some values in the database are NULL, which translate to NaN in python floating point variables. It appears that Grafana can’t handle this type of value. When I convert NaN to zero, I get results.

5

@rnoldr I’m glad to see you found a solution/workaround. Out of curiosity, are you actually running Grafana version 5 as stated in your initial post? That’s a few years old now, and IIRC an early version of Postgres support had just been introduced then. You’d be much better off using a more recent version, especially for Postgres data.