Part 5 
fetch all columns no additional filtering
add projection pushdown
add filtering pushdown


equijoin table A and B 

A = A1 U A2 U ... U An
B = B1 U B2 U ... U Am

k=0
foreach fragment Ai of A
   foreach fragment Bj of B
      joinList[k] = Ai join Bj
      sameNode[k] = false
      local[k] = false 
      if ( node(Ai) == node(Bj) )
         sameNode[k] = true
      if ( node(Ai) == local )
         local[k] = true;
      elsif ( node(Bi) == local )
         joinList[k] = Bj join Ai
         local[k] = true;

// there are now only 4 types of fragment joins to handle
// 1) sameNode == false and local == false
//          : both operands of join are remote and on different DB
// 2) sameNode == false and local == true 
//          : first operand of join is local and second is remote
// 3) sameNode == true and local == false 
//          : both operands are remote and on the same DB
// 4) sameNode == true and local == true 
//          : both operands are on the same local DB

foreach join operation join(i,j) of joinList
   if type 1 then
      create a temporary table for fragment i
      fetch entire fragment i into a temporary table
      follow the steps for type 2.

   elsif type 2 then
      fetch remote fragment j
      foreach row fetched from j
         query local fragment i to construct join 
         output join results

   elsif type 3 or type 4 then
      construct SQL query for join(i,j)
      send SQL query to remote/local db for processing
      output the results
   else error