Query takes forever to execute

Question

This query executes forever:
select count(*)
from VIEW_DOCUMENT
where exists
select VIEW_DOCUMENT_ITEM.documentID
from VIEW_DOCUMENT_ITEM
where VIEW_DOCUMENT_ITEM.documentID=VIEW_DOCUMENT.documentID
Here's what's inside VIEW_DOCUMENT_ITEM:
select *
from DOCUMENT_ITEM
join VIEW_USER
If I replace "join VIEW_USER" with "join USER" the query executes normally in few seconds!
This makes no sense because here's what's in VIEW_USER:
select * from USER
Does anybody know what are possible causes for this strange behaviour?

Answer 1

Actually my query is much more complex, this is simplified version.
In original query it's 100% not cartesian join.
Result of my query is 2710 and result of Sven's query is 2711.
My question is only why does joining a table work normally and why does joining a view "select * from table" take forever.
I can't see execution plan because my query never ends. I have to kill the Linux process.
Here is TKPROF output, I don't know what this stuff means:
TKPROF: Release 10.2.0.1.0 - Production on Tue Mar 4 14:21:57 2008
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Trace file: orcl_ora_29715.trc
Sort options: prsela  exeela  fchela 
count    = number of times OCI procedure was executed
cpu      = cpu time in seconds executing
elapsed  = elapsed time in seconds executing
disk     = number of physical reads of buffers from disk
query    = number of buffers gotten for consistent read
current  = number of buffers gotten in current mode (usually for update)
rows     = number of rows processed by the fetch or execute call
alter session set sql_trace true
call     count       cpu    elapsed       disk      query    current        rows
Parse        0      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        1      0.00       0.00          0          0          0           0
Misses in library cache during parse: 0
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 64 
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse        0      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        0      0.00       0.00          0          0          0           0
total        1      0.00       0.00          0          0          0           0
Misses in library cache during parse: 0
Misses in library cache during execute: 1
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call     count       cpu    elapsed       disk      query    current        rows
Parse       58      0.00       0.01          0          0          0           0
Execute    308      0.05       0.06          0          0          0           0
Fetch      758      0.03       0.16         38       1188          0        2086
total     1124      0.10       0.24         38       1188          0        2086
Misses in library cache during parse: 13
Misses in library cache during execute: 13
    1  user  SQL statements in session.
  308  internal SQL statements in session.
  309  SQL statements in session.
Trace file: orcl_ora_29715.trc
Trace file compatibility: 10.01.00
Sort options: prsela  exeela  fchela 
       1  session in tracefile.
       1  user  SQL statements in trace file.
     308  internal SQL statements in trace file.
     309  SQL statements in trace file.
      14  unique SQL statements in trace file.
    3007  lines in trace file.
       0  elapsed seconds in trace file.