pentaho: Error processing component : how to set parameter for piechart? - pentaho

Question

I want to make a dynamic piechart (that depends on date parameter) on dashboard on CDE.
First, here's an example of my BD:
ID date category
----------------------------
1 2019-01-01 positive
2 2019-01-01 positive
3 2019-01-01 negative
4 2019-01-01 zero
1 2019-02-01 positive
2 2019-02-01 zero
3 2019-02-01 negative
On datasource panel, I added a query below:
select category, count(category) from table where date=${date} group by category;
Then on component panel, I did :
On Datasource panel, I set the parameter in the same way:
But the piechart doesn't show and the error message is : Error processing component
If I replace the parameter ${month} with a value like '2019-01-01', the pie chart does show without problem.
I followed multiple tutorials but can't resolve my problem.
Is it because of date format ?
This is how I set date parameter on datasource panel:I also tried with Date instead of String...

Answer 1

My experience is that treating CDE parameters as strings and then converting them to date in the SQL query works best and gives you the most control.
MySQL example:
where STR_TO_DATE(${DATE_FROM}, '%d-%m-%Y') = MyDateColumn
In my case, I needed to show "dd-mm-yyyy" format in the dashboard and internationalization is rather broken in CDE, so I went with string parameters and the above contains the MySQL date format for it. If you use a different DB, look up the date conversion function in the docs.