Range partitioning and update to range value

Question

There is a V. large table on our system, where a column is initally set to NULL, but updated with sysdate when processed. The majority of qureies against this table are for those with NULL values. I'm considering range partitioning by this column, where all NULLs will appear in the one partition, all non_NULLs in the other. The questions are.....
1)will a row automatically move from one partion to the next on update of the NULL value
2) If so, what are the overheads

Answer 1

Using ENABLE ROW MOVEMENT will work, but the overhead of moving the rows is fairly high. If the date column is only updated once over the life of the record, then this overhead may be acceptable. However, if the date field is updated to sysdate most times the record is touched, then this may be a large performance hit.
You may want to investigate the use of a function based index to get the NULL dates indexed. A function like:
DECODE(date_field,NULL,1,NULL)
would create an index containing only the null rows. Then a query like:
SELECT stuff
FROM table
WHERE DECODE(date_field,NULL,1,NULL) = 1would likely do and index range scan.
TTFN
John