timestamp_value not working with MariaDB

[jgosmann]

Describe the bug
Trying to set timestamp_value with a query against a MariaDB database fails with this error message:

Error gathering metrics: [from Gatherer #1] [collector=my-collector,query=sql_exporter_test] sql: Scan error on column index 0, name \"time\": unsupported Scan, storing driver.Value type []uint8 into type *time.Time

To Reproduce

1. Create config for a metric:

   metrics:
     - metric_name: sql_exporter_test
       type: gauge
       help: foo
       static_value: 1
       timestamp_value: time
       query: |
         SELECT NOW() as time FROM dual;

2. Ensure that the queried database is a MariaDB database (didn't test any other databases, might not be a problem limited to MariaDB).
3. See sql_exporter logs.

Expected behavior
A metric with timestamps collected from the given timestamp_value column is created.

[burningalchemist]

Hey @jgosmann, thanks for reporting the issue.

Have you tried adding ?parseTime=true parameter to the DSN?

[jgosmann]

Yes, that solves the problem. Is this documented anywhere? Maybe it makes sense to mention that this might be necessary somewhere close where timestamp_value is described?

[burningalchemist]

Yeah, absolutely! I'll add it to the docs. It wasn't an issue with PostgreSQL and a few other DBs I was testing (e.g. sqlite). It's a driver thing, not something sql_exporter specific.

Sadly, I don't have resources to test all of them, so I have to rely upon the users. 😄👍

[burningalchemist]

I'll close the ticket and move it to Discussions (Q&A) as there's a quite nice library of answers already.

[burningalchemist]

The README has been updated.