Closing a ref cursor
Hello,
if i have:
function getPersoaneContact(v_id_client in clienti.id%type)
return ref_cursor is
tmp ref_cursor;
begin
open tmp for
select ........ from ..... where ....
return tmp;
end;Where should i close that ref cursor? Or.. should i close it?
Thanks!
Tom had already discussed about this.
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1606716582692
Regards,
Prazy
Similar Messages
-
Cursors are not closed when using Ref Cursor Query in a report ORA-01000
Dear Experts
Oracel database 11g,
developer suite 10.1.2.0.2,
application server 10.1.2.0.2,
Windows xp platform
For a long time, I'm hitting ORA-01000
I have a 2 group report (master and detail) using Ref Cusor query, when this report is run, I found that it opens several cursors (should be only one cursor) for the detail query although it should not, I found that the number of these cursors is equal to the number of master records.
Moreover, after the report is finished, these cursors are not closed, and they are increasing cumulatively each time I run the report, and finally the maximum number of open cursors is exceeded, and thus I get ORA-01000.
I increased the open cursors parameter for the database to an unbeleivable value 30000, but of course it will be exceeded during the session because the cursors are increasing cumulatively.
I Found that this problem is solved when using only one master Ref Cursor Query and create a breake group, the problem is solved also if we use SQL Query instead of Ref Query for the master and detail queries, but for some considerations, I should not use neither breake group nor SQL Query, I have to use REF Cursor queries.
Is this an oracle bug , and how can I overcome ?
Thanks
Edited by: Mostafa Abolaynain on May 6, 2012 9:58 AMThank you Inol for your answer, However
Ref Cursor give me felxibility to control the query, for example see the following query :
function QR_1RefCurDS return DEF_CURSORS.JOURHEAD_REFCUR is
temp_JOURHEAD DEF_CURSORS.JOURHEAD_refcur;
v_from_date DATE;
v_to_date DATE;
V_SERIAL_TYPE number;
begin
SELECT SERIAL_TYPE INTO V_SERIAL_TYPE
FROM ACC_VOUCHER_TYPES
where voucher_type='J'
and IDENT_NO=:IDENT
AND COMP_NO=TO_NUMBER(:COMPANY_NO);
IF :no_date=1 then
IF V_SERIAL_TYPE =1 THEN
open temp_JOURHEAD for select VOCH_NO, VOCH_DATE
FROM JOURHEAD
WHERE COMP_NO=TO_NUMBER(:COMPANY_NO)
AND IDENT=:IDENT
AND ((TO_NUMBER(VOCH_NO)=:FROM_NO and :FROM_NO IS NOT NULL AND :TO_NO IS NULL)
OR (TO_NUMBER(VOCH_NO) BETWEEN :FROM_NO AND :TO_NO and :FROM_NO IS NOT NULL AND :TO_NO IS NOT NULL )
OR (TO_NUMBER(VOCH_NO)<=:TO_NO and :FROM_NO IS NULL AND :TO_NO IS NOT NULL )
OR (:FROM_NO IS NULL AND :TO_NO IS NULL ))
ORDER BY TO_NUMBER(VOCH_NO);
ELSE
open temp_JOURHEAD for select VOCH_NO, VOCH_DATE
FROM JOURHEAD
WHERE COMP_NO=TO_NUMBER(:COMPANY_NO)
AND IDENT=:IDENT
AND ((VOCH_NO=:FROM_NO and :FROM_NO IS NOT NULL AND :TO_NO IS NULL)
OR (VOCH_NO BETWEEN :FROM_NO AND :TO_NO and :FROM_NO IS NOT NULL AND :TO_NO IS NOT NULL )
OR (VOCH_NO<=:TO_NO and :FROM_NO IS NULL AND :TO_NO IS NOT NULL )
OR (:FROM_NO IS NULL AND :TO_NO IS NULL ))
ORDER BY VOCH_NO;
END IF;
ELSE
v_from_date:=to_DATE(:from_date);
v_to_date:=to_DATE(:to_date);
IF V_SERIAL_TYPE =1 THEN
open temp_JOURHEAD for select VOCH_NO, VOCH_DATE
FROM JOURHEAD
WHERE COMP_NO=TO_NUMBER(:COMPANY_NO)
AND IDENT=:IDENT
AND ((voch_date between v_from_date and v_to_date and :from_date is not null and :to_date is not null)
OR (voch_date <= v_to_date and :from_date is null and :to_date is not null)
OR (voch_date = v_from_date and :from_date is not null and :to_date is null)
OR (:from_date is null and :to_date is null ))
ORDER BY VOCH_DATE,TO_NUMBER(VOCH_NO);
ELSE
open temp_JOURHEAD for select VOCH_NO, VOCH_DATE
FROM JOURHEAD
WHERE COMP_NO=TO_NUMBER(:COMPANY_NO)
AND IDENT=:IDENT
AND ((voch_date between v_from_date and v_to_date and :from_date is not null and :to_date is not null)
OR (voch_date <= v_to_date and :from_date is null and :to_date is not null)
OR (voch_date = v_from_date and :from_date is not null and :to_date is null)
OR (:from_date is null and :to_date is null ))
ORDER BY VOCH_DATE,VOCH_NO;
END IF;
END IF;
return temp_JOURHEAD;
end; -
Ref Cursor closed returning to Form
Hi,
I came across this old thread which seems to be an exact match for my problem.
sys ref cursor is closed
And whereas the solutions do work as stated there is an issue with it that i wonder if anyone here has since got around.
Take those examples and make the sql dynamic. on return to the form the ref cursor is instantaneouly closed for you making the thing unusable.
i.e.
OPEN cur FOR SELECT 'x' from dual
works just fine but
OPEN cur FOR 'SELECT ''X'' from dual'
resutls in an closed cursor the moment the ref cursor parameter returns to the form. I need the dynamic form because my cursor is truly built dynamically.
Any ideas anyone?Hi,
try this :
1. declare in the package specification
TYPE rec_view IS RECORD(
COL1 VARCHAR2(250),
COL2 VARCHAR2(250),
COL3 VARCHAR2(250),
COL4 VARCHAR2(250),
COL5 VARCHAR2(250)
TYPE t_ref_curs IS REF CURSOR RETURN rec_view;
TYPE t_rec_c IS REF CURSOR;
2. define the dynamic sql - procedure
PROCEDURE prc_getdata (p_refcur IN OUT t_ref_curs, p_result OUT VARCHAR2,
p_filter IN varchar2 DEFAULT NULL, p_orderby In VARCHAR2 DEFAULT NULL) IS
BEGIN
-- dyn cursor ! --
EXECUTE IMMEDIATE
'BEGIN
OPEN :a FOR ' ||
' select empno, ename, job, mgr, hiredate, sal from emp'||' '||
p_filter ||' '||
p_orderby ||'; '||
'END;'
USING p_refcur;
END prc_getdata;
3. define in the Form a PL/SQL based block on this procedure.
Hope it helps.
Best regards
Friedhold -
The query below will return values in the form of
bu seq eligible
22 2345 Y
22 2345 N
22 1288 N
22 1458 Y
22 1458 N
22 1234 Y
22 1333 N
What I am trying to accomplish is to loop through the records returned.
for each seq if there is a 'N' in the eligible column return no record for that seq
eg seq 2345 has 'Y' and 'N' thus no record should be returned.
seq 1234 has only a 'Y' then return the record
seq 1333 has 'N' so return no record.
How would I accomplish this with a ref Cursor and pass the values to the front end application.
Procedure InvalidNOs(io_CURSOR OUT T_CURSOR)
IS
v_CURSOR T_CURSOR;
BEGIN
OPEN v_CURSOR FOR
' select bu, seq, eligible ' ||
' from (select bu, seq, po, tunit, tdollar,eligible,max(eligible) over () re ' ||
' from (select bu, seq, po, tunit, tdollar,eligible ' ||
' from ( ' ||
' select bu, seq, po, tunit, tdollar, eligible, sum(qty) qty, sum(price*qty) dollars ' ||
' from ' ||
' ( select /*+ use_nl(t,h,d,s) */ ' ||
' h.business_unit_id bu, h.edi_sequence_id seq, d.edi_det_sequ_id dseq, ' ||
' s.edi_size_sequ_id sseq, h.po_number po, h.total_unit tUnit, h.total_amount tDollar, ' ||
' s.quantity qty, s.unit_price price,' ||
' (select (case when count(*) = 0 then ''Y'' else ''N'' end) ' ||
' from sewn.NT_edii_po_det_error ' ||
' where edi_det_sequ_id = d.edi_det_sequ_id ' ||
' ) eligible ' ||
' from sewn.nt_edii_purchase_size s, sewn.nt_edii_purchase_det d, ' ||
' sewn.nt_edii_purchase_hdr h, sewn.nt_edii_param_temp t ' ||
' where h.business_unit_id = t.business_unit_id ' ||
' and h.edi_sequence_id = t.edi_sequence_id ' ||
' and h.business_unit_id = d.business_unit_id ' ||
' and h.edi_sequence_id = d.edi_sequence_id ' ||
' and d.business_unit_id = s.business_unit_id ' ||
' and d.edi_sequence_id = s.edi_sequence_id ' ||
' and d.edi_det_sequ_id = s.edi_det_sequ_id ' ||
' ) group by bu, seq, po, tunit, tdollar, eligible ' ||
' ) ' ||
' group by bu, seq, po, tunit, tdollar, eligible)) ';
io_CURSOR := v_CURSOR;
END InvalidNOs;One remark why you should not use the assignment between ref cursor
variables.
(I remembered I saw already such thing in your code).
Technically you can do it but it does not make sense and it can confuse your results.
In the opposite to usual variables, when your assignment copies value
from one variable to another, cursor variables are pointers to the memory.
Because of this when you assign one cursor variable to another you just
duplicate memory pointers. You don't copy result sets. What you do for
one pointer is that you do for another and vice versa. They are the same.
I think the below example is self-explained:
SQL> /* usual variables */
SQL> declare
2 a number;
3 b number;
4 begin
5 a := 1;
6 b := a;
7 a := a + 1;
8 dbms_output.put_line('a = ' || a);
9 dbms_output.put_line('b = ' || b);
10 end;
11 /
a = 2
b = 1
PL/SQL procedure successfully completed.
SQL> /* cursor variables */
SQL> declare
2 a sys_refcursor;
3 b sys_refcursor;
4 begin
5 open a for select empno from emp;
6 b := a;
7 close b;
8
9 /* next action is impossible - cursor already closed */
10 /* a and b are the same ! */
11 close a;
12 end;
13 /
declare
ERROR at line 1:
ORA-01001: invalid cursor
ORA-06512: at line 11
SQL> declare
2 a sys_refcursor;
3 b sys_refcursor;
4 vempno emp.empno%type;
5
6 begin
7 open a for select empno from emp;
8 b := a;
9
10 /* Fetch first row from a */
11 fetch a into vempno;
12 dbms_output.put_line(vempno);
13
14 /* Fetch from b gives us SECOND row, not first -
15 a and b are the SAME */
16
17 fetch b into vempno;
18 dbms_output.put_line(vempno);
19
20
21 end;
22 /
7369
7499
PL/SQL procedure successfully completed.Rgds.
Message was edited by:
dnikiforov -
Problem with XSU when trying to execute pl/sql package returning ref cursor
Hi,
I'm exploring xsu with 8i database.
I tried running sample program which I took from oracle
documentation. Here is the details of these.
------create package returning ref cursor---
CREATE OR REPLACE package testRef is
Type empRef IS REF CURSOR;
function testRefCur return empRef;
End;
CREATE OR REPLACE package body testRef is
function testRefCur RETURN empREF is
a empREF;
begin
OPEN a FOR select * from emp;
return a;
end;
end;
---------package successfully created-----
Now I use java program to generate xml data from ref cursor
------------java program ----------
import org.w3c.dom.*;
import oracle.xml.parser.v2.*;
import java.sql.*;
import oracle.jdbc.driver.*;
import oracle.xml.sql.query.OracleXMLQuery;
import java.io.*;
public class REFCURt
public static void main(String[] argv)
throws SQLException
String str = null;
Connection conn = getConnection("scott","tiger"); //
create connection
// Create a ResultSet object by calling the PL/SQL function
CallableStatement stmt =
conn.prepareCall("begin ? := testRef.testRefCur();
end;");
stmt.registerOutParameter(1,OracleTypes.CURSOR); // set
the define type
stmt.execute(); // Execute the statement.
ResultSet rset = (ResultSet)stmt.getObject(1); // Get the
ResultSet
OracleXMLQuery qry = new OracleXMLQuery(conn,rset); //
prepare Query class
try
qry.setRaiseNoRowsException(true);
qry.setRaiseException(true);
qry.keepCursorState(true); // set options (keep the
cursor alive..
System.out.println("..before printing...");
while ((str = qry.getXMLString())!= null)
System.out.println(str);
catch(oracle.xml.sql.OracleXMLSQLNoRowsException ex)
System.out.println(" END OF OUTPUT ");
qry.close(); // close the query..!
// qry.close(); // close the query..!
// Note since we supplied the statement and resultset,
closing the
// OracleXMLquery instance will not close these. We would
need to
// explicitly close this ourselves..!
stmt.close();
conn.close();
// Get the connection given the user name and password..!
private static Connection getConnection(String user, String
passwd)
throws SQLException
DriverManager.registerDriver(new
oracle.jdbc.driver.OracleDriver());
Connection conn = DriverManager.getConnection
("jdbc:oracle:thin:@xxxx:1521:yyyy",user,passwd);
return conn;
when I ran the program after successful compilation,I got the
following error
==========
Exception in thread "main" oracle.xml.sql.OracleXMLSQLException:
1
at oracle.xml.sql.core.OracleXMLConvert.getXML(Compiled
Code)
at oracle.xml.sql.query.OracleXMLQuery.getXMLString
(OracleXMLQuery.java:263)
at oracle.xml.sql.query.OracleXMLQuery.getXMLString
(OracleXMLQuery.java:217)
at oracle.xml.sql.query.OracleXMLQuery.getXMLString
(OracleXMLQuery.java:194)
at REFCURt.main(Compiled Code)
============================
Can anybody tell me why I'm getting this error.Am I missing any
settings?
thanksWe are using 8.1.7 Oracle db with latest xdk loaded.
am I missing any settings? -
Hi All,
I have a requirement that i need to execute query having dynamic number of columns using Ref Cursor e.g.
v_string := 'PO_NUMBER , ORG_ID' ;
v_query := 'SELECT '|| v_string || 'FROM table_name';
Can someone please quide me how to define Type dynamically for the above requirement ?
Thanks
Vipul Maheshwarihope you understand how to use this with the help of ref cursor
CURSOR Expressions
A CURSORexpression returns a nested cursor. This form of expression is equivalent to
the PL/SQL REF CURSORand can be passed as a REF CURSORargument to a function.
A nested cursor is implicitly opened when the cursor expression is evaluated. For
example, if the cursor expression appears in a select list, a nested cursor will be
opened for each row fetched by the query. The nested cursor is closed only when:
■ The nested cursor is explicitly closed by the user
■ The parent cursor is reexecuted
■ The parent cursor is closed
■ The parent cursor is cancelled
■ An error arises during fetch on one of its parent cursors (it is closed as part of the
clean-up)
Restrictions on CURSOR Expressions The following restrictions apply to CURSOR
expressions:
■ If the enclosing statement is not a SELECTstatement, then nested cursors can
appear only as REF CURSORarguments of a procedure.
■ If the enclosing statement is a SELECTstatement, then nested cursors can also
appear in the outermost select list of the query specification or in the outermost
select list of another nested cursor.
■ Nested cursors cannot appear in views.
■ You cannot perform BINDand EXECUTEoperations on nested cursors.
Examples The following example shows the use of a CURSORexpression in the
select list of a query:
SELECT department_name, CURSOR(SELECT salary, commission_pct
FROM employees e
WHERE e.department_id = d.department_id)
FROM departments d
ORDER BY department_name;
The next example shows the use of a CURSORexpression as a function argument. The
example begins by creating a function in the sample OEschema that can accept the
REF CURSORargument. (The PL/SQL function body is shown in italics.)
CREATE FUNCTION f(cur SYS_REFCURSOR, mgr_hiredate DATE)
RETURN NUMBER IS
emp_hiredate DATE;
before number :=0;
after number:=0;
begin
loop
fetch cur into emp_hiredate;
exit when cur%NOTFOUND;
if emp_hiredate > mgr_hiredate then
after:=after+1;
else
before:=before+1;
end if;
end loop;
close cur;
if before > after then
return 1;
else
return 0;
end if;
end;
The function accepts a cursor and a date. The function expects the cursor to be a query
returning a set of dates. The following query uses the function to find those managers
in the sample employeestable, most of whose employees were hired before the
manager.
SELECT e1.last_name FROM employees e1
WHERE f(
CURSOR(SELECT e2.hire_date FROM employees e2
WHERE e1.employee_id = e2.manager_id),
e1.hire_date) = 1
ORDER BY last_name; -
Ref Cursors in a stored Procedure
Can some help me with an answer to the below question.
How many ref cursors can be declared in a stored procedure in oracle?
Thanksuser533016 wrote:
You are right. Keeping so many cursors open is not good at all. But i was doing this to see where it breaks and is there something that definitely controls the number of refcursors in allowed a PL/SQL block.As Karthick already mentioned you have the OPEN_CURSORS parameter which defines how many open cursors you may have in any one session.
However, this doesn't just apply to Ref Cursors. If you open explicitly defined cursors then this will also count towards that, as well as issuing select statements as they are implicit cursors... e.g.
declare
cursor c1 is
select * from emp;
cursor c2 is
select * from dept;
v_c1 c1%ROWTYPE;
v_c2 c2%ROWTYPE;
v_cnt number;
begin
open c1; -- now we have 1 open cursors
loop
fetch c1 into v_c1;
exit when c1%notfound;
open c2; -- now we have 2 open cursors
loop
fetch c2 into v_c2;
exit when c2%notfound;
select count(*) -- this counts as opening cursor number 3.
into v_cnt
from payroll;
-- after the select statement the implicit cursor is automatically closed, so now we have 2 open again
end loop;
close c2; -- after this we just have 1 more open
end loop;
close c1; -- after this we have no open cursors
end; -
Populate a REF CURSOR from regular cursor...
Hi all,
I apologize if the answer to this is somewhere...I've been looking on the web for sometime and can't find an answer to the following problem. I have a Significant Events database that contains network based issues and problems. As problems are detected on the network an SE is issued and published. As the SE records are updated, NEW records are entered into the table and "linked" back to the original. Each update results in a new row. Thus, an SE with two updates would have a total of 3 lines. When the SE gets closed (set the column CLOSED to SYSDATE), only the "original" SE is closed, any updates are left open...aka, the CLOSED column is left null.
That said, I need a way to get the original and/or latest updated SE rows from the table. Thus, I am trying to use a PL/SQL package. The PL/SQL "must" return a REF CURSOR as the results are being passed to a client process.
My initial approach was within a PL/SQL procedure, I have an SQL statement that returns the SE originals. Once in that cursor I need to do the following:
- Attempt to fetch any linked SE rows.
- if no rows then
- add the original to the REF CURSOR.
- else
- find latest SE update
- add latest SE update to REF CURSOR.
- end if
My Question is : How do I manually "add" a row to a REF CURSOR?
If this is not possible, is there a way to populate a REF CURSOR from maybe another construct like:
TYPE ian_se_record is RECORD (
se_id number
,linked_se_id number
,submitted date
,updated date
,closed date
,segroup varchar2(150)
,incident_start_time varchar2(150)
,business_units_affected varchar2(150)
,officenum varchar2(1500)
,sedetails varchar2(4000)
TYPE ian_se_table is table of ian_se_record index by binary_integer;
With the above construct I could:
- Fill ian_se_table with the process described above.
- And finally select off ian_se_table into the REF CURSOR?
Any help would be greatly appreciated,
adymHi michaels,
I've put your solution in place, but can't seem to get it to run. The two types were moved out of the package and into real types as you said. Here's the function, for brevity, I've remove some of the less important code:
function ian_se_fetch return sys_refcursor
is
p_csr_events sys_refcursor;
cursor csr_items is
select
se_id
...removed for brevity...
/* END : csr_items */
ian_se_row ian_se_record;
ian_se_tbl ian_se_table;
l_lng_index number;
l_lng_linked number;
l_lng_id number;
begin
* OPEN : Open the main cursor of originals...
for the_item in csr_items loop
* CHECK : Check for any updates to the original...
l_lng_linked := 0;
select count(*)
into l_lng_linked
from sig_se_t src
where src.linked_se_id = the_item.se_id;
l_lng_id := 0; /* reset the se-id */
/* SE original...no linked records yet. */
if ( l_lng_linked = 0 ) then
l_lng_id := the_item.se_id;
/* SE updates...one or more updates are present. */
else
begin
select
se_id
into l_lng_id
from sig_se_t src
where src.linked_se_id = the_item.se_id
and rownum = 1
order by updated desc; /* latest update */
exception
when too_many_rows then
l_lng_id := the_item.se_id;
when others then
l_lng_id := 0;
end;
end if;
if ( l_lng_id != 0 ) then
select
se_id
,linked_se_id
,submitted
,updated
,closed
,segroup
,incident_start_time
,business_units_affected
,officenum || decode( nvl(impact,'1')
,'1',''
,decode(impact
,'NA', ''
,':' || impact
) impact
,sedetails
into ian_se_row.se_id
,ian_se_row.linked_se_id
,ian_se_row.submitted
,ian_se_row.updated
,ian_se_row.closed
,ian_se_row.segroup
,ian_se_row.incident_start_time
,ian_se_row.business_units_affected
,ian_se_row.officenum
,ian_se_row.sedetails
from sig_se_t src
where src.se_id = l_lng_id;
l_lng_index := nvl(ian_se_tbl.last,0)+1;
ian_se_tbl(l_lng_index).se_id := ian_se_row.se_id;
ian_se_tbl(l_lng_index).linked_se_id := ian_se_row.linked_se_id;
ian_se_tbl(l_lng_index).submitted := ian_se_row.submitted;
ian_se_tbl(l_lng_index).updated := ian_se_row.updated;
ian_se_tbl(l_lng_index).closed := ian_se_row.closed;
ian_se_tbl(l_lng_index).segroup := ian_se_row.segroup;
ian_se_tbl(l_lng_index).incident_start_time := ian_se_row.incident_start_time;
ian_se_tbl(l_lng_index).business_units_affected := ian_se_row.business_units_affected;
ian_se_tbl(l_lng_index).officenum := ian_se_row.officenum;
ian_se_tbl(l_lng_index).sedetails := ian_se_row.sedetails;
end if;
end loop;
* REF CURSOR : Open the ref cursor on the dataset...
if ( nvl(ian_se_tbl.last,0) = 0 ) then
p_csr_events := null;
else
open p_csr_events for
select *
from table (cast ( ian_se_tbl as ian_se_table ));
end if;
return p_csr_events;
end;Here's the test. I keep getting the same error ORA-06530:
SQL> variable v refcursor;
SQL> exec :v:=pkg_ian.ian_se_fetch;
BEGIN :v:=pkg_ian.ian_se_fetch; END;
ERROR at line 1:
ORA-06530: Reference to uninitialized composite
ORA-06512: at "N0002501.PKG_IAN", line 131
ORA-06512: at line 1
SQL> print v
ERROR:
ORA-24338: statement handle not executedOther things I tried:
- The ian_se_fetch() function was a procedure using an in out parameter...same error.
- Wrote a small anonymous block and tried to LOOP/FETCH. Same ORA-06530 error.
P.S. Line 131 of pkg_ian is the SELECT ... INTO ian_se_row.se_id, ...
Any help would be greatly appreciated,
tia,
adym
Message was edited by:
alink -
Ref cursors for stored procedure
Hi every body,
I am new one,I am in learning stage.
My java developer was ask me give set of results.
i am using in my code sys_refcursor, my questions are.
SQL> create or replace procedure sysref(p_out out sys_refcursor) is
2 begin
3 open p_out for select empno,ename from employee;
4 end;
5 /
I am using the procedure like above procedure.
1) How to use ref cursors in procedure. what is the main use.
2) How to close ref cursors in procedure.If it is need.
3) How to use exceptions in procedures for ref cursors.
Give me one example with complete structure.
Please help me
new one
Edited by: subba on Aug 19, 2010 12:08 AM
Edited by: subba on Aug 19, 2010 12:09 AMsubba wrote:
1) How to use ref cursors in procedure. what is the main use.All SQL in Oracle are parsed as cursors in the Shared Pool. The client code (be that PL/SQL or Visual Basic or Java) gets a handle or reference to this SQL cursor on the server.
Using this handle, the client can fetch rows using the cursor (the cursor is like a program - the executable binary version of the source SQL code).
Clients implement their interfaces with this SQL cursor handle in different ways. PL/SQL alone supports:
- implicit cursor handles
- explicit cursor handles
- DBMS_SQL cursor handles
- reference cursor handles
Why so many? Different tools for different jobs. Each has its pros and cons and each is suited for specific (and different) types of problems.
A ref cursor is special in that PL/SQL can pass this SQL cursor reference handle to an external client to use - like Java.
Why?
The basic concept is that of abstraction. Removing the complexities of SQL and the database design and SQL optimisation from the Java code. Instead, Java calls a PL/SQL proc. This proc creates the SQL cursor, and uses a reference cursor variable to store the SQL cursor handle. It can then pass this to Java. This means that the entire SQL is encapsulated in the PL/SQL proc. We can now modify it, optimise it, support data models changes in the database via the PL/SQL proc... all without even having to recompile the Java code that makes the call and consumes the ref cursor the PL/SQL proc gives it.
2) How to close ref cursors in procedure.If it is need.Yes. A very important factor - well spotted.
As PL/SQL can pass ref cursors to external clients. it does not automatically close these cursors. It does not know when the client has consumed the cursor. It will only close it when the cursor is still open, when the Oracle server session is terminated.
So it is important that the client (Java in this case) closes the cursor when done. If not, the cursor will remain open, will continue to occupy server resources... and if the client opens more and more of these cursors, the server process will run out of resources.
Cursor leakage by Java developers are common - and can simply be avoided by closing the cursor once the Java code has consumed it.
3) How to use exceptions in procedures for ref cursors.No. Why? Why would you want to deal with the exception in a PL/SQL proc? The Java code wants to open that cursor. It knows why. It knows what to do when that cursor fails or is empty. It interacts with the user. How is the PL./SQL proc, whose only function is to construct the SQL and pass the cursor handle to Java, to know any of this?
Exceptions in this regard should typically be handled in Java. Not in PL/SQL.
Of course, if that PL/SQL proc has parameters, it also needs to validate these and it needs to raise application exceptions to inform the Java caller when these parameters are invalid.
But actually catching exception in this case... does not make much sense. As what can the PL/SQL do about the error when it is a "server" and Java is the "client"?
It is like saying that the Oracle Server should handle all exceptions when TOAD is used and incorrect SQL is passed to it. How does it make sense for Oracle to process SQL errors and the TOAD client not getting any results from a wrong SQL and not knowing that there was even an error with that SQL? -
Q: NULL return REF CURSOR from a PL/SQL function
I was told that PL/SQL does not handle properly NULL REF CURSORS.
Here's my implementation in a PL/SQL package
PACKAGE SPEC:
TYPE z_rec IS RECORD (
TYPE z_cur IS REF CUR RETURN z_rec;
FUNCTION some_function(
p_msg OUT VARCHAR2)
RETURN z_cur;
PACKAGE BODY:
FUNCTION some_function(
p_msg OUT VARCHAR2)
RETURN z_cur
IS
retval z_cur;
OPEN retval FOR
SELECT ...
-- Successfull data retrieval
p_msg := NULL;
RETURN retval;
EXCEPTION
WHEN OTHERS THEN
p_msg := SUBSTR( SQLERRM, 1, 255 );
RETURN NULL;
END some_function;
I am expecting that a user of this function would call it and test p_msg (output parameter)
1. IS NULL p_msg it means there were no errors encounetered. The returned cursor can be NULL though (i.e. no records retrieved)
2. IS NOT NULL p_msg, it means that there were errors and the returned cursor is not usable.
My question is:
what are the pitfalls of this approach?
Thanks a lot.user10817976 wrote:
I asked and still waiting for the answer.
retval z_cur;
What I am afraid for is that
OPEN retval FOR
SELECT ...
EXCEPTION
retval := NULL;
tries to open the cursor. What happens in case of error? Well, I imagine retval is still NULL. Do I need to (try) to close the cursor in the EXCEPTION section (in order not to misuse the number of cursors in the pool?) That's my worry.No.
If there is an error opening the cursor the cursor will not be open and will not need closing.
The code should simply be
function some_function
return z_cur
is
retval z_cur;
begin
open retval for
select ...
return retval;
end some_function; It is bad practice for a function to have output parameters.
It is bad practice to turn exceptions into return codes.
http://tkyte.blogspot.com/2008/06/when-others-then-null-redux.html
Remember everyone, everyone remember, keep in mind:
When others not followed by RAISE or RAISE_APPLICATION_ERROR is almost certainly, with 99.999999999% degree of accuracy, a bug in your developed code. Just say "no" to when others not followed by raise or raise_application_error!Read the links, it leads to problems over and over again. -
Forms Data-Block based on stored procedures - REF CURSOR feature NOT FUNCTIONING
This topic is related to another topic in this forum titled "FORMS HOW TO SET QUERY SOURCE ARGUMENTS??" I posted my message there as well. I am posting as a NEW TOPIC so that it catches the attention of Oracle Support.
I built a data form based on a stored procedure and REF CURSOR IN OUT parameter.
My procedure takes a IN parameter to fill in the criteria for the OPEN <cursor_variable> select ... where ... statement.
In the Value setting of the Query source Arguments , I set the VALUE to ":BLOCK_NAME.ITEM_NAME" at design time to supply the input value to the procedure. this works to the extent of making available the form item value to the stored procedure parameter. I verified this by doing an insert into some debug table , of the incoming parameter value inside my stored procedure.
The cursor gets opened properly into the REF cursor variable. I verified this by fetching a record into a local variable and inserting the value into a debug table again in the stored procedure.
(I took care to close and re-open the REF cursor variable again - so that the front-end can continue to fetch it from the first record. )
***** PROBLEM **************
But the front end forms runtime is giving me a FRM-40301 - query returned no records even though the REF cursor is returned properly opened.
Did anybody else face the same problem ??
Please post what you found.
Thanks,
Shankaran
nullThis topic is discussed at length in another thread "How Set Value For Query DataSource Arguments?"
But I am posting the findings here as well.
THIS TOPIC IS CLOSED.
My Bad. The problem Cause : I did not include all columns in the
cursor rowtype in the Data-block. In the wizard for the data block , I selected ONLY the columns that I needed. But I was doing a Select * from <my_table> in my open cursor <Cursor-Variable> .... The <Cursor Variable>
itself was declared <my_table>%rowtype
FIX : The Data Block structure (columns included as items) should match the cursor record Structure. One may or may not
display all the columns in the LAYOUT though.
But I don't understand why it gives such a misleading message like FRM-40301 Query retrieved no records. Oracle Team fix it.
Hope this helps people who face the same problem.
Thanks, -
hi friends,
can somebody tell ,if i want find out my Ref Cursor having data or not.
can i use like below.never tried.
REFCURSORNAME%ROWCOUNT > 0;
if it is there other way please let me know with some example.
--RajnishIt is up to whatever calls the procedure or function to determine whether the returned cursor has rows or not. As Karthik says, the only way to do that is to fetch a row.
The procedure that is opening the cursor to return to a caller cannot do that because the caller would then not get the first row returned unless the called function closed and re-opened the cursor before returning it. However, it is possible that between opening the cursor and and fetching a row to determine if the cursor has records and re-opening it to return to the caller some other process has deleted all of the rows os the cursor will be empty this time.
John -
STORED PROCEDURE/REF CURSOR: How to output entire buffer
I wrote a Stored Procedure wherein I use a Cursor to extract multiple
rows and columns. I then write them into the buffer
(dmbs_output.put_line). But when I try to capture the entire result
into an OUT variable, I only get the last buffered line.
So how do I output the entire buffer- all rows and columns? In other words (maybe), how do I use dbms_output.get_lines() to assign value to an OUT variable?
Alternatively, using REF CURSOR as OUT variable, I added the following to "CREATE OR REPLACE PROCEDURE ... ()":
cursor_out_test OUT cursor_test
But when I tried:
DEFINE CURSOR TYPE cursor_test IS REF CURSOR RETURN table%ROWTYPE;
...or...
DECLARE TYPE cursor_test IS REF CURSOR RETURN table%ROWTYPE;
I still got syntax errors.
In one line, what I am trying to do is break the result array at the database level rather than at the application level.
Cheers, Bill
http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14261/sqloperations.htm#LNPLS00605I did the following:
OPEN CURSOR x
LOOP
FETCH CURSOR x INTO col1, col2
(EXIT WHEN...)
variable_line := col1 || col2
END LOOP
CLOSE CURSOR
But after closing this cursor, variable_line contains only the last buffered line. I want all the looped lines (without using associative arrays, nested tables etc). So I guess I am just looking for some way to append data lines- adding chr(10) doesn't work either.
Cheers, Bill -
Cast error message when discovering ref cursor parameter from stored proced
We are today using Microsoft's Oracle provider with some code from the old Data Application Block (from MSDN) to discover parameters from the stored procedures. This code uses the OracleCommandBuilder.DeriveParameters to get the parameters from the stored procedure and command.Parameters.CopyTo copies the discovered parameters into the command object.
If I test with a simple function returning a ref cursor I get one parameter with type refCursor and ParameterDirection.OutPut. This is working fine as long we where using Microsoft's Oracle provider. But using Oracle ODP .NET I get the following error message on datadapter.Fill (I fill a dataset with the result from the reference cursor)
Unable to cast object of Type 'Oracle.DataAccess.Client.OracleDataReader' to type 'Oracle.DataAccess.Types.OracleRefCursor.
If I create a ref parameter manualy like this:
OracleParameter myrefCursor = new OracleParameter();
myrefCursor .OracleDbType = OracleDbType.RefCursor;
myrefCursor .ParameterName = "myParameterName";
myrefCursor .Direction = ParameterDirection.ReturnValue;
and add it to the command object this is working OK. So it seems to be a problem with discovering ref cursor parameters from the database, other parameter types is OK.. I have compared the properties of my manual ref cursor parameter with the one discovered from the stored procedure, but I cannot see any difference. (I see the Value property has some values for the discovered one, but I have set this to DBNull.Value without any result)
Any ideas why I get this error code? Is there any other code blocks I can use to discover the parameters? We send in params object[] with the different values into the helper class and the value is added to the parameter. (Se I don't need to set the data type etc for each parameter, I just need to have the correct order of the parameters)For accuracy's sake, just wanted to let everyone know that this is actually a bug. The correct bug number is 8423178.
Christian
Mark_Williams wrote:
Just to follow-up on this issue...
The bug has been closed as "not a bug" as it seems undocumented behavior was relied upon for this to work in earlier releases.
Note from the documentation on DeriveParameters:
"The output values of derived parameters return as .NET Types by default. To obtain output parameters as provider types, the OracleDbType property of the parameter must be set explicitly by the application to override this default behavior. One quick way to do this is to set the OracleDbType to itself for all output parameters that should be returned as provider types." (emphasis added)
The issue, as you might already know, is that there is no corresponding .NET Framework Type for an Oracle Ref Cursor and the type is, therefore, set to Object. So, explicitly setting the type to OracleDbType.RefCursor should work.
Regards,
Mark -
REF CURSOR to Associative Array
I have a procedure that builds up a collection (associative array / index-by table). Is there any way to hand the collection over to ODP.NET without putting the contents into a temporary table? REF CURSOR seems to fit, but I cannot find the syntax to OPEN a REF CURSOR for the collection.
I am trying to turn the GetResourceGroup() a_Resources parameter into a ref cursor in the example below (which, as I understand it, would also hold the collection in memory until the cursor is closed).
Alternatively, is there a direct method? I.e. is it possible to get the collection directly into a DataTable or similar?
Any advice gratefully received,
Peter
TYPE RsrcRow IS RECORD
ResourceId Resource.ResourceId%TYPE,
ResourceName Resource.ResourceName%TYPE
TYPE Resources IS TABLE OF RsrcRow INDEX BY VARCHAR2(80);
PROCEDURE GetResourceGroup(
a_ResourceType IN VARCHAR2,
a_Resources OUT Resources
IS
l_LocalCollection Resources;
BEGIN
GetResourcesByType(a_ResourceType, l_LocalCollection);
-- Return resource set (need to port this to ODP.NET).
a_Resources := l_LocalCollection;
RETURN;
END GetResourceGroup;odp.net does not have collection support right now.
PL/SQL Associative Array should be available in next release (see other forum threads)
1. Support for Varchar2 indexes is unlikely (since OCI does not provide such functionality). Which means you can only return an C style "array" like structure at best.
2. Your 'GetResourceGroup' need to return REF CURSOR (or other primitive type like VARCHAR2), until Associative Array become available.
FB
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