fix compilation failure opt_mapreduce.mx:141: '=' : conversion from 'size_t' to 'int', possible loss of data
fix compilation failure opt_mapreduce.mx:141: '=' : conversion from 'size_t' to 'int', possible loss of data

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb