Cannot sort X-Axis on a bar chart if X-axis is a var_string (MySQL)

[mason-gordon]

Version: 3.1.3

My problem: Superset is interpreting varchar columns from MySQL as var_string, which when used in a bar chart, can only be sorted alphabetically. There is no way to sort the X-axis by a metric, even when explicitly adding a metric to the sort by field.

My company is trialing Superset and while messing around with charts, I ran into a very annoying bug when trying to create bar charts. We have two data sources, one in Postgres and the other in MySQL. For any query written against the MySQL database, almost every varchar column is imported into Superset as a var_string data type. Whenever I use a column with var_string as the X-axis for a bar chart, I am not given an option to sort the X-axis. If I manually drag a metric to the "Sort By" field, the data still refuses to be sorted by that measure. It seems that the X-axis is always sorted alphabetically, which is almost never useful. The chart I am trying to create is just looking at total hours assigned to departments.

I've tried casting the columns as CHAR(50) or any other number and it doesn't change anything. Oddly enough, there is one single column that is correctly interpreted as a string, and it only has 3 characters. Attempting to cast other varchar columns to 3 characters does not work. I have no issues with data from Postgres - I can easily use any text column as the X-axis for a bar chart and sort the X-axis by my metrics.

Any ideas why this is happening?

[mason-gordon]

Found the answer -https://github.com/apache/superset/blob/master/superset/db_engine_specs/mysql.py#L27

Looks like the data converter for MySQL only converts TINYTEXT, MEDIUMTEXT, and LONGTEXT to String. Most of our string columns in MySQL are VARCHARs, so it's not being processed as a String for Superset's purposes.