Invalid column type in Pentaho

A java.sql.SQLException: Invalid column type error in pentaho had broken a previously functioning report upon the introduction of changes.

On close inspection, I traced the problem to a newly introduced a parameter in an SQL statement. The parameter was supplying data for use in a SQL IN(...) clause. When a variable of type string-list was supplied, the report worked. The exception above was thrown when a variable of type string was supplied.

To resolve the problem, I created a Java ArrayList to hold the single value and hence ensure that the variable supplied was always a list.