If true, each input record will be directly compared against EVERY record in the reference table. This may produce slightly ...

If true, each input record will be directly compared against EVERY record in the reference table.  This may produce slightly better results, but will be extremely slow unless the number of records in the reference table is very small.  Note that the entire reference table will be loaded into main memory if this option is enabled.  This option is primarily intended for debugging purposes and should be used with care.