Currently it's only possible to use "contains" as comparison method on String attributes. However with very large autonumbers (e.g. starting at 1 million) users want to be able to search using only the last few digits. Currently this is only possible if you copy the value from the AutoNumber to a string attribute, creating duplicate data in the process.
It would be great if datagrid search fields would support "contains" on numeric attributes
Check out my custom widget: Data Grid Search Filters
It just so happens to do 'contains' searching on autonumber fields.