fix external gby to not open the writer twice

git-svn-id: https://hyracks.googlecode.com/svn/branches/fullstack_asterix_stabilization@3110 123451ca-8445-de46-9d55-352943316053
1 file changed
tree: e1ed3d39732a450d9e81adcfc21414b80fd6c356
  1. algebricks/
  2. hivesterix/
  3. hyracks/
  4. pom.xml
  5. pregelix/