Rather than just say "it's a hashref", provide a simple example of what that
hashref might look like.
$source->add_columns('col1' => \%col1_info, 'col2' => \%col2_info, ...);
+ $source->add_columns(
+ 'col1' => { data_type => 'integer', is_nullable => 1, ... },
+ 'col2' => { data_type => 'text', is_auto_increment => 1, ... },
+ );
+
Adds columns to the result source. If supplied colname => hashref
pairs, uses the hashref as the L</column_info> for that column. Repeated
calls of this method will add more columns, not replace them.