#open database pgraph2;
#query meminit (1524);
#query p2 loadgraph;

# Queries the top 5 co-authors of publications of "Ralf Hartmut Gueting"
# The results will be grouped and show the Authors with the sum of
# joint publications.

# As the node a2 is specifying a unique property (Name)m the corresponding
# index will be used to the accelerate the query. For comparision see
# match2-coauthors-slow not using the index. 

query p2 
match2 ['
(
   ( a )
   ( a2 ( (Name "Ralf Hartmut Gueting") ))
   (doc Document)
   (a2  AUTHOR_OF doc)
   (a  AUTHOR_OF doc)
)',
'(  ((a Name) <> "Ralf Hartmut Gueting")  ) ',
'(  ((a Name) Name)  )'] 
sortby[Name] groupby[Name; Cnt:group count] sortby[Cnt:desc] head[5] consume;