I have a cursor which fetches records from a table.
open p_cursor for select a1, a2 from my_table;
Thereafter I use fetch to get the columns and put all of them into a single CLOB column as follows : ( add_to_clob is a procedure which concatenates a text into existing CLOB - my_clob )
fetch p_cursor into l_a1, l_a2;
add_to_clob ( my_clob, l_a1 );
add_to_clob ( my_clob, l_a2 );
Essentially - the output of fetch are being written into a large CLOB.
But the operation is running slower than expected; and we have millions of records to process.
Is there any way such that use of cursor can be avoided to that the process runs faster ?
You can "cheat" a bit and use some XML aggregate functions like this:
DECLARE
l_clob1 CLOB;
l_clob2 CLOB;
BEGIN
SELECT XMLSERIALIZE(CONTENT EXTRACT(XMLAGG(XMLELEMENT(COL1, ao.object_name||', ')), '/COL1/text()') AS CLOB),
XMLSERIALIZE(CONTENT EXTRACT(XMLAGG(XMLELEMENT(COL2, ao.edition_name||', ')), '/COL2/text()') AS CLOB)
INTO l_clob1, l_clob2
FROM all_objects ao
WHERE ROWNUM <= 10;
END;
/
Just replace the simple query with your own. Also, you'll need to
Related
I wrote a stored procedure, but I don't think it is performing at all. How can I make it work better? Thanks.
Table A has 800k records. Table B has 36k records. Is test data, there will be more records in production environment.
Table B has customer_no column index defined.
I ran it once and it took 22 minutes.
create or replace procedure SP_KVKK
is
TYPE json_data_type IS RECORD
(
del_data CLOB
);
customer_no number(10);
r_del_data C%ROWTYPE;
l_deleted_cur SYS_REFCURSOR;
l_deleted_rec json_data_type;
l_sel_sql VARCHAR2 (500);
cursor mbb_list is
select customer_no from A;
begin
open mbb_list;
loop
fetch mbb_list into customer_no;
exit when mbb_list%notfound;
l_sel_sql := 'SELECT JSON_OBJECT(* RETURNING CLOB) AS DEL_DATA
FROM B where customer_no=' || customer_no;
open l_deleted_cur for l_sel_sql;
loop
fetch l_deleted_cur into l_deleted_rec;
exit when l_deleted_cur%notfound;
r_del_data.DELETED_DOCUMENT_JSON := l_deleted_rec.del_data;
r_del_data.DELETE_DATE := SYSTIMESTAMP;
Insert into C
values r_del_data;
end loop;
close l_deleted_cur;
end loop;
close mbb_list;
end;
The best thing you can do is deal with this construct as a single SQL statement. Stop thinking in terms of row-by-row nested loops which will always be slow, and look to SQL batch operations to handle this:
begin
-- insert your two columns into table C using the data
-- from table B returned as a json_object and systimestamp,
-- where only records from table B that have a customer_no
-- from table A will be selected
insert into C (deleted_document_json, delete_date)
select json_object(B.* returning clob), systimestamp
from B
inner join A using (customer_no);
commit;
end;
Say I have a stored procedure which accepts 2 varchars, does some processing and updates my business tables. Is there a way that I can run the stored procedure for the results from a select query?
Like,
execute my_stored_proc select varchar_1,varchar_2 from an_ip_table;
You can iterate over results by loop
BEGIN
FOR RECS IN (SELECT varchar_1, varchar_2 FROM an_ip_table)
LOOP
my_stored_proc (RECS.varchar_1, RECS.varchar_2);
END LOOP;
END
This could be a simple way:
begin
for i in (
select varchar_1, varchar_2
from an_ip_table
)
loop
my_stored_proc(i.varchar_1, i.varchar_2);
end loop;
end;
Initially, I thought of just to put a comment, but this needs some explanation, so I'm writing an answer. You are actually doing it the wrong way. Ideally, you should be passing a cursor to your my_stored_proc and fetching the cursor inside the procedure. Your method actually causes multiple calls to procedure for every row from the query result. The processing will be very slow if you have huge volume of data. It is a bad idea even if there are few rows.
Here is a sample procedure that does a dml operation using FORALL.It is just a sample, but you should be able to convert your select query such that you should be able to do dml this way.
CREATE OR REPLACE PROCEDURE my_stored_proc (
p_iptab_cur SYS_REFCURSOR
) AS
TYPE iprec IS RECORD ( col1 an_ip_table.col1%TYPE,
col2 an_ip_table.col1%TYPE );
TYPE iptype IS
TABLE OF iprec;
ips iptype;
BEGIN
FETCH p_iptab_cur BULK COLLECT INTO ips;
FORALL i IN ips.FIRST..ips.LAST
--Your DML-- using the collection of records.
END;
/
--Calling the procedure by passing the `CURSOR`
DECLARE
x SYS_REFCURSOR;
BEGIN
OPEN x FOR select col1, col2
from an_ip_table;
my_stored_proc(x);
END;
/
I need to open a cursor while table name, columns and where clause are varying. The table name etc will be passed as parameter. For example
CURSOR batch_cur
IS
SELECT a.col_1, b.col_1
FROM table_1 a inner join table_2 b
ON a.col_2 = b.col_2
WHERE a.col_3 = 123
Here, projected columns, table names, join criteria and where clause will be passed as parameters. Once opened, i need to loop through and process each fetched record.
You need to use dynamic SQL something like this:
procedure dynamic_proc
( p_table_1 varchar2
, p_table_2 varchar2
, p_value number
)
is
batch_cur sys_refcursor;
begin
open batch_cur for
'select a.col_1, b.col_1
from ' || p_table_1 || ' a inner join || ' p_table_2 || ' b
on a.col_2 = b.col_2
where a.col_3 = :bind_value1';
using p_value;
-- Now fetch data from batch_cur...
end;
Note the use of a bind variable for the data value - very important if you will re-use this many times with different values.
From your question i guess you need a dynamic cursor. Oracle provides REFCURSOR for dynamic sql statements. Since your query will be built dynamically you need a refcursor to do that.
create procedure SP_REF_CHECK(v_col1 number,v_col2 date,v_tab1 number,v_var1 char,v_var2 varchar2)
is
Ref_cur is REF CURSOR;
My_cur Ref_cur;
My_type Table_name%rowtype;
stmt varchar2(500);
begin
stmt:='select :1,:2 from :3 where :4=:5';
open My_cur for stmt using v_col1,v_col2,v_tab1,v_var1,v_var2;
loop
fetch My_cur into My_type;
//do some processing //
exit when My_cur%notfound;
end loop;
close My_cur;
end;
Check this link for more http://docs.oracle.com/cd/B10500_01/appdev.920/a96624/11_dynam.htm
I've found a good question at https://dba.stackexchange.com/questions/3587/oracle-automate-export-unload-of-data. Is it valid to use such a construction:
FOR r IN (SELECT * FROM table) LOOP
UTL_FILE.PUT_LINE(lfFilelog, r.row);
END LOOP;
I'm trying to use something like this:
CREATE OR REPLACE PROCEDURE p_name(DESTFOLDER in varchar2, FILENAME in varchar2)
IS
V_FILEHANDLE UTL_FILE.FILE_TYPE;
CURSOR dataset IS
SELECT
field1,
field2,
fieldN
FROM
table1,
table2,
(SELECT field3 from table3);
-- WHERE CLAUSE ... and so on..
BEGIN
V_FILEHANDLE := UTL_FILE.FOPEN(DESTFOLDER, FILENAME, 'w');
FOR R IN dataset LOOP
UTL_FILE.PUT_LINE(V_FILEHANDLE, R.ROW);
END LOOP;
END;
/
and getting pls-00302 error which states that I should have defined ROW component. So as far as I undrestand this field should already exist in the query. Am I right?
Can I simply write a row from the cursor?
The answer mentionned is not complete, I think it was given as an example (pseudo-code) that lacks implementation details.
As it is:
your SELECT clause is invalid, you aren't selecting anything. What do you want to select?
the construct XX.row where xx is a cursor doesn't exist
furthermore, the UTL_FILE.get_line procedure accepts a VARCHAR2 as its second argument, not any kind of rowtype
you can't name a table table (although you could name it "table").
Given a table mytable(col1, col2, ... , colN) you could write:
CREATE OR REPLACE PROCEDURE p_name()
IS
V_FILEHANDLE UTL_FILE.FILE_TYPE;
CURSOR dataset IS SELECT col1, col2, /*...*/ coln FROM mytable;
BEGIN
/*utl_file.fopen maybe?*/
FOR R IN dataset LOOP
UTL_FILE.PUT_LINE(V_FILEHANDLE, R.col1 ||';'|| r.col2 /*...*/ || r.coln);
END LOOP;
END;
I have to write an Oracle procedure which should invoke an Oracle function returning REF_CURSOR. The function is declared like that
FUNCTION "IMPACTNET"."TF_CONVERTPARA" (PARASTRING IN NVARCHAR2) RETURN SYS_REFCURSOR
AS
c SYS_REFCURSOR;
BEGIN
OPEN c FOR
SELECT SUBSTR(element, 1, INSTR(element, '|') - 1) as key,
SUBSTR(element, INSTR(element, '|') + 1, 99999) as val
FROM (
SELECT REGEXP_SUBSTR(PARASTRING, '[^;]+', 1, LEVEL) element
FROM dual
CONNECT BY LEVEL < LENGTH(REGEXP_REPLACE(PARASTRING, '[^;]+')) + 1
);
RETURN c;
END;
Can you tell me what I need to write in order to invoke the function from within my procedure? I'd like to insert all the returned values (shaped a table with two columns) into a rational table.
Thank you in advance!
Something along the lines of this should work (obviously, I'm guessing about table names and column names and the exact logic that you're trying to implement)
CREATE PROCEDURE some_procedure_name
AS
l_rc SYS_REFCURSOR := impactnet.tf_convertpara( <<some string>> );
l_key VARCHAR2(100);
l_val VARCHAR2(100);
BEGIN
LOOP
FETCH l_rc
INTO l_key, l_val;
EXIT WHEN l_rc%notfound;
INSERT INTO some_table( key_column, val_column )
VALUES( l_key, l_val );
END LOOP;
END;
As Ollie points out, it would be more efficient to do a BULK COLLECT and a FORALL. If you're just dealing with a few thousand rows (since your function is just parsing the data in a delimited string, I'm assuming you expect relatively few rows to be returned), the performance difference is probably minimal. But if you're processing more data, the difference can be quite noticeable. Depending on the Oracle version and your specific requirements, you may be able to simplify the INSERT statement in the FORALL to insert a record rather than listing each column from the record individually.
CREATE PROCEDURE some_procedure_name
AS
TYPE key_val_rec
IS RECORD(
key VARCHAR2(100),
val VARCHAR2(100)
);
TYPE key_val_coll
IS TABLE OF key_val_rec;
l_rc SYS_REFCURSOR := impactnet.tf_convertpara( <<some string>> );
l_coll key_val_coll;
BEGIN
LOOP
FETCH l_rc
BULK COLLECT INTO l_coll
LIMIT 100;
EXIT WHEN l_coll.count = 0;
FORALL i IN l_coll.FIRST .. l_coll.LAST
INSERT INTO some_table( key_column, val_column )
VALUES( l_coll(i).key, l_coll(i).val );
END LOOP;
END;