View difference between Paste ID: zzSU4X7J and mcHrsBB5

 CREATE OR replace FUNCTION left_shift( p_val INT8,
                                       p_shift INT8) returns int8
 AS
   $$
   DECLARE
   BEGIN
     RETURN trunc(p_val * power(2,p_shift));
   END;
   $$ LANGUAGE 'plpgsql' immutable;
 
 CREATE OR replace FUNCTION morton (p_col INT8,
                                    p_row INT8) returns int8
 AS
   $$
   /*  this procedure calculates the Morton number of a cell
 at the given row and col[umn]
 Written:  D.M. Mark, Jan 1984;
 Converted to Vax/VMS: July 1985
 Converted to PostgreSQL, Simon Greener, 2010
 */
   DECLARE
     v_row int8 := 0;
     v_col int8 := 0;
     v_key int8;
     v_level int8;
     v_left_bit int8;
     v_right_bit int8;
     v_quadrant int8;
   BEGIN
     v_row := p_row;
     v_col := p_col;
     v_key := 0;
     v_level := 0;
     WHILE ((v_row>0)
     OR
     (
       v_col>0
     )
     )
     LOOP
       /* Split off the row (left_bit) and column (right_bit) bits and
 then combine them to form a bit-pair representing the quadrant */
       v_left_bit := v_row % 2;
       v_right_bit := v_col % 2;
       v_quadrant := v_right_bit + 2*v_left_bit;
       v_key := v_key            + left_shift( v_quadrant,( 2 * v_level ) );
       /* row, column, and level are then modified before the loop continues */
       v_row := v_row     / 2;
       v_col := v_col     / 2;
       v_level := v_level + 1;
     END LOOP;
     RETURN (v_key);
   END;
   $$ LANGUAGE 'plpgsql' immutable;