LEFT OUTER JOIN with SubQuery

Question

I have two tables and I want to return all data from the first table with a piece of information from the second based on an effective date being at least a certain value. The tables I am working with contain billions of rows so I need a solution that will also scale.
Sample tables:
create table pp ( x number, y number);
create table ec ( x number, y number, effdate date);
insert into pp values (1,2);
insert into pp values (2,3);
insert into pp values (1,3);
insert into ec values (1,2,sysdate);
insert into ec values (2,3,sysdate);
insert into ec values (1,3,sysdate+365);
commit;
select * from pp, ec where pp.x = ec.x(+) and pp.y=ec.y(+)
and (effdate = ( select max(effdate) from ec ecc where ecc.y=ec.y and ecc.x = ec.x and effdate < sysdate) or effdate is null);
The above query (and the one below) returns two rows. it does not return where the date does not meet the criteria.
select * from pp LEFT OUTER JOIN ec ON pp.x = ec.x and pp.y=ec.y
WHERE (effdate = ( select max(effdate) from ec ecc where ecc.y=ec.y and ecc.x = ec.x and effdate < sysdate) or effdate is null);
This returns the three rows BUT IS VERY SLOW when run against the billion+ row table (because we cannot correlate the subquery results.)
select * from pp LEFT OUTER JOIN (SELECT x, y, effdate
FROM ec WHERE effDate = (SELECT MAX(EFFdate) from ec ecc where ecc.y=ec.y and ecc.x = ec.x and effdate < sysdate)) c ON c.x = pp.x and c.y = pp.y;

Answer 1

It would help quite a bit to know
1) your Oracle version
2) your indexes and data volumes (do BOTH tables have billions of rows?)
But here's something that may perform faster.
ME_XE? WITH Maximizied AS
  2  (
  3     SELECT
  4        MAX(EffDate),
  5        x,
  6        y
  7     FROM ec
  8     WHERE EffDate < SYSDATE
  9     GROUP BY x, y
10  )
11  SELECT *
12  FROM pp p, Maximizied m
13  WHERE p.x = m.x (+)
14  AND   p.y = m.y (+);
                 X                  Y MAX(EFFDAT                  X                  Y
                 2                  3 05-29-2008                  2                  3
                 1                  2 05-29-2008                  1                  2
                 1                  3
3 rows selected.
Elapsed: 00:00:00.03