Javaの実装 - Advanced SQL Engine - Teradata Database

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.teradata.fnc.Context;
import com.teradata.fnc.Phase;
import com.ncr.teradata.fnc.*;
import java.io.Serializable;

class Element
{
   public int v;
}

class AGR_Storage implements Serializable
{
   public long current_value; // Current moving sum total
   public int next; // Location to store next detail row
   public int tptr; // Trailing buffer pointer
   public int count; // Number of detail rows processed
   public long window_size; // Moving window size
   public List<Element> data;
   public int heap; // Heap area to store window rows
   public AGR_Storage(int a, int b, int c, int d, long e, int f)
   {
      current_value = a;
      next = b;
      tptr = c;
      count = d;
      window_size = e;
      data = new ArrayList<Element>(100);
      heap = f;

   }
}

public class MySumClass
{
   final private static boolean debug = true;
   public static int MySum(Phase phase, Context context[], int x)
   {
      int result = 0;
      try
      {
         AGR_Storage s1 = null;
         AGR_Storage s2 = null;
         int i, t_x;

         if (phase.getPhase() != Phase.AGR_INIT && phase.getPhase()!= Phase.AGR_NODATA)
            s1 = (AGR_Storage) context[0].getObject(1);

         switch (phase.getPhase())
         {
            case Phase.AGR_INIT:
               if (debug)
               {
                  System.err.println("Phase: AGR_INIT");
               }
               s1 = new AGR_Storage(0,0,0,0,0,0);

               context[0].initCtx(s1);
               s1.window_size = context[0].getWindowSize();
               if(s1.window_size > 0)
               {
                  for (i=0; i < s1.window_size; i++) //initialize heap
                  {
                     s1.data.get(i).v = 0;
                  }
               }
               // fall through

            case Phase.AGR_DETAIL:
               t_x = x;
               if (s1.window_size < 0) // non moving case
               {
                  s1.current_value += t_x;
               }
               else // Moving
               {
                  s1.count++;
                  if (s1.count > s1.window_size) // Remove value row from window
                  {
                     s1.current_value -= s1.data.get(s1.tptr).v;
                     s1.tptr = (int)inc(s1.tptr, (int) s1.window_size);
                  }
                  s1.current_value += t_x; // Add row to window
                  s1.data.get(s1.next).v = t_x;
                  s1.next = (int) inc(s1.next, (int) s1.window_size);
               }

               break;

            case Phase.AGR_COMBINE:

            case Phase.AGR_FINAL:
               result = (int) s1.current_value;
               return result;

            case Phase.AGR_MOVINGTRAIL:
               s1.current_value -= s1.data.get(s1.tptr).v;
               s1.tptr = (int) inc(s1.tptr,(int)s1.window_size);
               break;

            case Phase.AGR_NODATA:
               if (debug)
                  System.err.println("Phase: AGR_NODATA");
               return 0;

            default:

               throw new SQLException("Invalid Phase", "U0005");

         }

         context[0].setObject(1, s1);
      }
      catch (Exception e)
      {
         e.printStackTrace();
      }
      return result;
   }


   private static long inc(int next, int size)
   {
      return (next + 1) % size;
   }

}