How to Optimize PL/SQL code using Bulk collect/FORALL? - sql

Question

pl/sql code taking too much time to remove characters in all tables
begin
for i in ( select TABLE_NAME,COLUMN_NAME from all_tab_columns
where owner='BILL' and data_length > 1 and table_name not like 'SYS_EXPORT_SCHEMA%' and table_name not like 'BIN%' and data_type ='VARCHAR2'
and column_name not like '%RR_NO%' and column_name not like '%RRNO%' order by 5 desc )
loop
execute immediate 'UPDATE '|| i.TABLE_NAME || ' SET ' ||i.COLUMN_NAME || '= REPLACE (' ||i.COLUMN_NAME ||',CHR(10),'||chr(39)||chr(39)|| ') WHERE INSTR('||i.COLUMN_NAME ||',CHR(10))>0';
execute immediate 'UPDATE '|| i.TABLE_NAME || ' SET ' ||i.COLUMN_NAME || '= REPLACE (' ||i.COLUMN_NAME ||',CHR(13),'||chr(39)||chr(39)|| ') WHERE INSTR('||i.COLUMN_NAME ||',CHR(13))>0';
dbms_output.put_line(i.TABLE_NAME||' - '||i.COLUMN_NAME||'- '||sql%rowcount);
end loop;
commit;
end;
pls help me by writing using Bulk collect/FORALL
Right now i am doing Manually using
select ' UPDATE '|| TABLE_NAME || ' SET ' ||COLUMN_NAME || '= REPLACE (' ||COLUMN_NAME ||',CHR(10),'||chr(39)||chr(39)|| ') WHERE INSTR('||COLUMN_NAME ||',CHR(10))>0;'
from all_tab_columns
where owner='BILL' and data_length > 1 and table_name not like 'SYS_EXPORT_SCHEMA%' and table_name not like 'BIN%'
and data_type ='VARCHAR2' and column_name not like '%RR_NO%' and column_name not like '%RRNO%';
select ' UPDATE '|| TABLE_NAME || ' SET ' ||COLUMN_NAME || '= REPLACE (' ||COLUMN_NAME ||',CHR(13),'||chr(39)||chr(39)|| ') WHERE INSTR('||COLUMN_NAME ||',CHR(13))>0;'
from all_tab_columns
where owner='BILL' and data_length > 1 and table_name not like 'SYS_EXPORT_SCHEMA%'
and table_name not like 'BIN%' and data_type ='VARCHAR2' and column_name not like '%RR_NO%' and column_name not like '%RRNO%';
copying this SQL results and executing manually.
it was taking more than 1 hour to run scripts.
DECLARE
CURSOR c1 IS SELECT TABLE_NAME,COLUMN_NAME FROM ALL_TAB_COLUMNS
WHERE OWNER='BILL' AND DATA_LENGTH > 1 AND TABLE_NAME NOT LIKE 'SYS_EXPORT_SCHEMA%' AND TABLE_NAME NOT LIKE 'BIN%' AND DATA_TYPE ='VARCHAR2'
AND COLUMN_NAME NOT LIKE '%RR_NO%' AND COLUMN_NAME NOT LIKE '%RRNO%';
TYPE RecList IS TABLE OF c1%ROWTYPE;
recs RecList;
BEGIN
BEGIN
OPEN c1;
LOOP
FETCH c1 BULK COLLECT INTO recs LIMIT 500;
EXIT WHEN c1%NOTFOUND;
FOR i IN recs.FIRST .. recs.LAST
LOOP
EXECUTE IMMEDIATE 'UPDATE '|| recs(i).TABLE_NAME || ' SET ' ||recs(i).COLUMN_NAME || '= REPLACE (' ||recs(i).COLUMN_NAME ||',CHR(10),'||CHR(39)||CHR(39)|| ') WHERE INSTR('||recs(i).COLUMN_NAME ||',CHR(10))>0';
dbms_output.put_line(recs(i).TABLE_NAME||' - '||recs(i).COLUMN_NAME||' - '||sql%rowcount);
EXECUTE IMMEDIATE 'UPDATE '|| recs(i).TABLE_NAME || ' SET ' ||recs(i).COLUMN_NAME || '= REPLACE (' ||recs(i).COLUMN_NAME ||',CHR(13),'||CHR(39)||CHR(39)|| ') WHERE INSTR('||recs(i).COLUMN_NAME ||',CHR(13))>0';
dbms_output.put_line(recs(i).TABLE_NAME||' - '||recs(i).COLUMN_NAME||' - '||sql%rowcount);
END LOOP;
END LOOP;
exception when others then
dbms_output.put_line(sqlcode||sqlerrm);
CLOSE C1;
END;
commit;
END;
/
i written one query Is's working,Is there any tips to optimize this query further.

Answer 1

The below is not tested but it just to give you an idea, try to prepare the values first send add them to the update. then make sure you have an index on the table covering the column. when you use functions it will make harder for the DML to read indexes. also in such way you are using bind variable method (soft parsing) which it will enhance the performance much better.
select REPLACE (' ||i.COLUMN_NAME ||',CHR(10),'||chr(39)||chr(39)|| ') into R_COL from dual;
select INSTR('||i.COLUMN_NAME ||',CHR(10)) into I_COL from dual;
UPDATE '|| i.TABLE_NAME || ' SET ' ||i.COLUMN_NAME || ' = R_COL WHERE I_COL >0;