Re: Library Cache

On Dec 29, 11:10 am, mrdjmag...@xxxxxxx wrote:
On Dec 29, 11:03 am, "gym dot scuba dot kennedy at gmail"





<kenned...@xxxxxxxxxxx> wrote:
<mrdjmag...@xxxxxxx> wrote in message

news:3e0d392e-2c18-4ad2-b9d2-36273b652062@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Dec 29, 9:09 am, Mark D Powell <Mark.Pow...@xxxxxxx> wrote:

On Dec 29, 9:53 am, mrdjmag...@xxxxxxx wrote:

Hi,

We installed this Spotlight for Oracle software. The software shows
an 85% re-parse rate against the Library Cache. Here is the biggest
issue we have. I do not think anything can be done, but maybe another
brain can figure something out:

We have a table with stored queries:
Row 1: SELECT emp_num FROM employees
Row 2: SELECT address FROM customer_address

We have a criteria table which holds any criteria that the query MAY
use:
Row 1: WHERE emp_first =
Row 1: AND emp_last =
Row 2: WHERE customer_id =

So, the PHP code can pass any number of parameters to the procedure,
which the procedure can parse and form the query and open a cursor for
the PHP code to read.

This means that the queries may/may not be the same, and need to be re-
parsed. So, we lose on that. Is there anything that can be done to
tune these and make them faster? An index against every possible
combination is not possible, and we have hundreds of these stored
queries........

Any smarter people have any ideas?

Arthur

If the SQL built from the logic includes constants for the where
clause conditions you could change it to use bind variables in the
code. This would give you some reuse.

You could replace the SQL in tables with SQL housed in stored
procedures that determines the SQL to be submitted based on the
parameters passed in. These statements would all use bind variables.
The procedures could pass cursors back to the application.

Take a look at the value of your database parameter cursor_sharing.
The default is EXACT. You might be able to get some benefit from
changing it to SIMILAR or FORCE. SQL plan changes are possible if
this parameter is changed so some tuning may be required.

HTH -- Mark D Powell --

Mark,

How about a query done like this:

   v_optin_str :=  'SELECT COUNT(*) FROM email_list a
                    WHERE '||v_date_clause||' '||v_adid_clause||
                          ' AND customer_id IS NOT NULL
                            AND adid IS NOT NULL
                            AND EXISTS (SELECT user_session
                                        FROM EMAIL_ALERTS b
                                        WHERE alert_type = ''OI''
                                        AND b.user_session =
a.user_session)';

   EXECUTE IMMEDIATE v_optin_str
   INTO stats_tab(199)
   USING p_b_date, p_e_date;

Is that correctly using the bind variables?

Ugly, very ugly.  No that isn't using bind variables.  You need
:bind_variable_name.

Yeah, we had some seriously *** programmers........time for an ALL
STORED PROCEDURE fix.

Basically where ever there is dynamic SQL, it can be replaced by bind
variables.

Just curious, what is the real difference between using "v_variable"
and "USING :v_variable" if the values get replaced?- Hide quoted text -

- Show quoted text -

One becomes a string literal and one does not:

SQL> create or replace procedure nobind_example(p_var in varchar2)
2 is
3 v_sqlstr varchar2(2000);
4 v_rec_ct number;
5
6 begin
7 v_sqlstr:='select count(*) from emp where ename = '''||
p_var||'''';
8
9 dbms_output.put_line(v_sqlstr);
10
11 execute immediate v_sqlstr
12 into v_rec_ct;
13
14 dbms_output.put_line(v_rec_ct);
15
16 end;
17 /

Procedure created.

SQL>
SQL> create or replace procedure bind_example(p_var in varchar2)
2 is
3 v_sqlstr varchar2(2000);
4 v_rec_ct number;
5
6 begin
7 v_sqlstr:='select count(*) from emp where ename = :1';
8
9 dbms_output.put_line(v_sqlstr);
10
11 execute immediate v_sqlstr
12 into v_rec_ct
13 using p_var;
14
15 dbms_output.put_line(v_rec_ct);
16
17 end;
18 /

Procedure created.

SQL>
SQL> set serveroutput on size 1000000
SQL>
SQL> exec nobind_example('ALLEN')
select count(*) from emp where ename = 'ALLEN'
1

PL/SQL procedure successfully completed.

SQL> exec bind_example('ALLEN')
select count(*) from emp where ename = :1
1

PL/SQL procedure successfully completed.

SQL>

Thus the second example generates a query which can be reused with
differing passed parameter values; the first does not.


David Fitzjarrell
.

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