How is it possibile that a max in a subquery gets a ORA-01652?

Question

I've got a very complex query
Let's suppose having three tables whose alias are x, y and z (and others tables)
Inside the WHERE of the query I've got something like:
x.x2 = (select max(y.y2) from mytable y where y.y1 = z.z1)
If I try to execute it on a single key, after a while I get a
ORA-01652: unable to extend temp segment by ...
if I try to change the line above with this:
x.x2 = constant
and then I execute it, I get the result within few seconds.
Even if I change the line with this:
x.x2 in (select y.y2 from table y where y.y1 = z.z1)
the query works, even if I get more rows.
How is it possibile that the MAX in the subquery makes the whole of the query not to work?
My Oracle version is 8i
Thanks!

Answer 1

You can easily answer this question by looking at the PLAN for this statement.
MAX uses a SORT operation and sort will use temporary segment, if the memory required exceeds the PGA.
Sybrand Bakker
Senior Oracle DBA