[Bug] Dashboard fails to display data when timestamp/datetime columns contain NULL values

[EdwardArchive]

Describe the bug

Dashboards fail to display data with error "This dashboard currently has no data to display. This may be due to access permissions." when timestamp or datetime columns contain NULL values.

To Reproduce

1. Create a source with timestamp/datetime column containing NULL values:
   CREATE TABLE events (
   id INT,
   event_time TIMESTAMP -- Contains NULL values
   );
   INSERT INTO events VALUES (1, NULL), (2, '2024-01-01 10:00:00');
2. Create a Rill source connecting to this table
3. Create a dashboard using this source
4. Dashboard displays: "This dashboard currently has no data to display. This may be due to access permissions."

Expected behavior

Dashboard should display data even when timestamp/datetime columns contain NULL values (e.g., by grouping NULL timestamps together), or show a clear error message indicating the NULL value issue instead of a misleading permissions error.

Environment:

• OS: Linux 6.14.0-1017-oem
• Rill Version: v0.80.0
• Affected databases: DuckDB, StarRocks (confirmed), likely others

Additional context

• Same table with no NULL values in timestamp columns works fine
• Issue occurs regardless of database type (DuckDB, StarRocks) and it will occur in orders
• Error message is misleading (mentions permissions instead of data issue)

Screenshots

• Some timestamps are NULL(or NOT NULL)

• All timestamps are NULL(This dashboard currently has no data to display. This may be due to access permissions.)

[EdwardArchive]

Hi team,
How can I approach to fix this issue?

I think there are three ways to approach this:

1. Improve error message — Add context about NULL timestamps instead of the misleading "access permissions" message
2. Catch NULL timestamps explicitly — Validate during query execution and return a descriptive error guiding users to filter/coalesce NULLs
3. Support NULL timestamps in dashboard — Filter NULLs from time-series but still show them in aggregate metrics
   I'd suggest starting with (1) and considering (2) as a follow-up.

Is there any good idea?

cc. @k-anshul
Hi sorry for the tagging, is there any good idea for this. I think step 2 and 3 will be the huge change.

[k-anshul]

Thanks for the report @EdwardArchive

We will take a look and get back to you.