title: Which is faster in Apache Pig: Split then Union or Filter and Left Join?
body: <p>I am currently processing a large input table (10^7 rows) in Pig Latin where the table is filtered on some field, processed and the processed rows are returned back into the original table. When the processed rows are returned back into the original table the fields the filters are based on are changed so that in subsequent filtering the processed fields are ignored. </p>
  
  <p>Is it more efficient in Apache Pig to first split the processed and unprocessed tables on the filtering criteria, apply processing and union the two tables back together or to filter the first table, apply the process to the filtered table and perform a left join back into the original table using a primary key?</p>