Learning PL/SQL

Driven by application PL/SQL troubleshooting, as the Pro*C doesn't work .  while succeeds to OPEN CURSOR for a very complex SQL in less than 1 second (manually run it takes few minutes). The processing part is taken care by PRO*C.

From http://docstore.mik.ua/orelly/oracle/langpkt/ch01_09.htm, it says,
"You must open an explicit cursor before you can fetch rows from that cursor. When the cursor is opened, the processing includes the PARSE, BIND, OPEN, and EXECUTE statements. This OPEN processing includes: determining an execution plan, associating host variables and cursor parameters with the placeholders in the SQL statement, determining the result set, and, finally, setting the current row pointer to the first row in the result set. "



However, I doubt "the processing" includes " EXECUTE . Reason being, from my 10046 tracing comparison of  without FETCH or with FETCH,  there is no EXECUTION PLAN showed for without FETCH.

alter session set events '10046 trace name context forever, level 12' ;

     OPEN emp_cv FOR SELECT first_name, salary FROM employees where employee_id < emp_id;


--WITHOUT fetch

SELECT FIRST_NAME, SALARY
FROM
 EMPLOYEES WHERE EMPLOYEE_ID < :B1


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      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        2      0.00       0.00          0          0          0           0

Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 33     (recursive depth: 1)
********************************************************************************

alter session set events '10046 trace name context off'

--corresponding 10046 trace file of WITHOUT FETCH processing

=====================
PARSING IN CURSOR #1 len=65 dep=1 uid=33 oct=3 lid=33 tim=1242222958636520 hv=3716011877 ad='4cd98690'
SELECT FIRST_NAME, SALARY FROM EMPLOYEES WHERE EMPLOYEE_ID < :B1
END OF STMT
PARSE #1:c=0,e=71,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1242222958636514
BINDS #1:
kkscoacd
 Bind#0
  oacdty=02 mxl=22(21) mxlc=00 mal=00 scl=00 pre=00
  oacflg=03 fl2=1206001 frm=00 csi=00 siz=24 off=0
  kxsbbbfp=f6fe60ac  bln=22  avl=03  flg=05
  value=106
EXEC #1:c=0,e=144,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,tim=1242222958636745
WAIT #3: nam='SQL*Net message to client' ela= 5 driver id=1650815232 #bytes=1 p3=0 obj#=-1 tim=1242222958636793
EXEC #3:c=10000,e=3030,p=0,cr=0,cu=0,mis=1,r=1,dep=0,og=1,tim=1242222958636870
WAIT #3: nam='SQL*Net message from client' ela= 236 driver id=1650815232 #bytes=1 p3=0 obj#=-1 tim=1242222958637166



-- with  FETCH processing

    OPEN emp_cv FOR SELECT first_name, salary FROM employees where employee_id < emp_id;
     loop
      fetch emp_cv into emp_dataPkg.er;
     exit when emp_cv%notfound;
      dbms_output.put_line(emp_dataPkg.er.name || ' - ' || emp_dataPkg.er.sal);
    end loop;
   CLOSE emp_cv;








********************************************************************************

SELECT FIRST_NAME, SALARY
FROM
 EMPLOYEES WHERE EMPLOYEE_ID < :B1


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        7      0.00       0.00          0         13          0           6
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        9      0.00       0.00          0         13          0           6

Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 33     (recursive depth: 1)

Rows     Row Source Operation
-------  ---------------------------------------------------
      6  TABLE ACCESS BY INDEX ROWID EMPLOYEES (cr=13 pr=0 pw=0 time=104 us)
      6   INDEX RANGE SCAN EMP_EMP_ID_PK (cr=7 pr=0 pw=0 time=120 us)(object id 12082)

********************************************************************************

select condition
from
 cdef$ where rowid=:1


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        1      0.00       0.00          0          2          0           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        3      0.00       0.00          0          2          0           1

Misses in library cache during parse: 0
Optimizer mode: CHOOSE
Parsing user id: SYS   (recursive depth: 2)

Rows     Row Source Operation
-------  ---------------------------------------------------
      1  TABLE ACCESS BY USER ROWID CDEF$ (cr=1 pr=0 pw=0 time=67 us)

********************************************************************************

alter session set events '10046 trace name context off';

--corresponding 10046 trace file of WITH FETCH processing

=====================
PARSING IN CURSOR #1 len=65 dep=1 uid=33 oct=3 lid=33 tim=1242222802758295 hv=3716011877 ad='4cd98690'
SELECT FIRST_NAME, SALARY FROM EMPLOYEES WHERE EMPLOYEE_ID < :B1
END OF STMT
PARSE #1:c=0,e=548,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=1,tim=1242222802758286
=====================
PARSING IN CURSOR #4 len=42 dep=2 uid=0 oct=3 lid=0 tim=1242222802759562 hv=844002283 ad='4cf6f080'
select condition from cdef$ where rowid=:1
END OF STMT
PARSE #4:c=0,e=123,p=0,cr=0,cu=0,mis=0,r=0,dep=2,og=4,tim=1242222802759554
BINDS #4:
kkscoacd
 Bind#0
  oacdty=11 mxl=16(16) mxlc=00 mal=00 scl=00 pre=00
  oacflg=18 fl2=0001 frm=00 csi=00 siz=16 off=0
  kxsbbbfp=f6f62148  bln=16  avl=16  flg=05
  value=00006F44.001D.0001
EXEC #4:c=0,e=362,p=0,cr=0,cu=0,mis=0,r=0,dep=2,og=4,tim=1242222802760102
FETCH #4:c=0,e=99,p=0,cr=2,cu=0,mis=0,r=1,dep=2,og=4,tim=1242222802760255
STAT #4 id=1 cnt=1 pid=0 pos=1 obj=31 op='TABLE ACCESS BY USER ROWID CDEF$ (cr=1 pr=0 pw=0 time=67 us)'
BINDS #1:
kkscoacd
 Bind#0
  oacdty=02 mxl=22(21) mxlc=00 mal=00 scl=00 pre=00
  oacflg=03 fl2=1206001 frm=00 csi=00 siz=24 off=0
  kxsbbbfp=f6f6254c  bln=22  avl=03  flg=05
  value=106
EXEC #1:c=0,e=3997,p=0,cr=2,cu=0,mis=1,r=0,dep=1,og=1,tim=1242222802762431
FETCH #1:c=0,e=108,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802762631
FETCH #1:c=0,e=24,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802762862
FETCH #1:c=0,e=18,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802762950
FETCH #1:c=0,e=15,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802763030
FETCH #1:c=0,e=14,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802763108
FETCH #1:c=0,e=15,p=0,cr=2,cu=0,mis=0,r=1,dep=1,og=1,tim=1242222802763185
FETCH #1:c=0,e=9,p=0,cr=1,cu=0,mis=0,r=0,dep=1,og=1,tim=1242222802763257
STAT #1 id=1 cnt=6 pid=0 pos=1 obj=12080 op='TABLE ACCESS BY INDEX ROWID EMPLOYEES (cr=13 pr=0 pw=0 time=104 us)'
STAT #1 id=2 cnt=6 pid=1 pos=1 obj=12082 op='INDEX RANGE SCAN EMP_EMP_ID_PK (cr=7 pr=0 pw=0 time=120 us)'
WAIT #3: nam='SQL*Net message to client' ela= 10 driver id=1650815232 #bytes=1 p3=0 obj#=-1 tim=1242222802763502
EXEC #3:c=10000,e=6638,p=0,cr=15,cu=0,mis=0,r=1,dep=0,og=1,tim=1242222802763589
WAIT #3: nam='SQL*Net message from client' ela= 359 driver id=1650815232 #bytes=1 p3=0 obj#=-1 tim=1242222802764056
=====================