Dear Techies,
Our application triggers queries like below very frequently.
select name,emp_id,prod_id,prod_name, .... from appuser.table where emp_id=:1 and prod_id=:2;
We usually spend ample amount of time finding the SQL_ID when we receive the problematic SQL_TEXT. We have an option in SQL*Plus for variables like emp_id, prodnum, etc.. as below
VARIABLE emp_id NUMBER; EXEC :emp_id := 101;
However, we have :1, :2 as bind variables name which can't be set before running the SQL as these are mere number (although treated as bind variables by Oracle). We can't ask Application vendor to rebuild all queries removing these numbered bind variables.
So, I was looking for any of the below option in SQL*Plus:
How to declare/define such bind variables (:1, :2, etc...) before running the SQL?
Can we bypass in any way the bind values and send this SQL to cursor cache in Oracle? Looks to be difficult but still wanted to give a try asking.
Can we pass the values of these bind variables (:1, :2, etc..) during runtime as we do in Toad & SQL developer? This way we can track the correct SQL_ID from the cursor (v$sql).
I have been trying and searching for various options but didn't get specific to mine. Any help in this regard would be greatly appreciated. Any version of Oracle database which addresses this concern would be fine.
Related
First off, my background is in SQL Server. Using CTEs (Common Table Expressions) is a breeze and converting it to a stored procedure with variables doesn't require any changes to the structure of the SQL other than replacing entered values with variable names.
In Oracle PL/SQL however, it is a completely different matter. My CTEs work fine as straight SQL, but once I try to wrap them as PL/SQL I run into a host of issues. From my understanding, a SELECT now needs an INTO which will only hold the results of a single record. However, I am wanting the entire recordset of multiple values.
My apologies if I am missing the obvious here. I'm thinking that 99% of my problem is the paradigm shift I need to make.
Given the following example:
NOTE: I am greatly over simplifying the SQL here. I do know the below example can be done in a single SQL statement. The actual SQL is much more complex. It's the fundamentals I am looking for here.
WITH A as (SELECT * FROM EMPLOYEES WHERE DEPARTMENT = 200),
B as (SELECT * FROM A WHERE EMPLOYEE_START_DATE > date '2014-02-01'),
C as (SELECT * FROM B WHERE EMPLOYEE_TYPE = 'SALARY')
SELECT 'COUNTS' as Total,
(SELECT COUNT(*) FROM A) as 'DEPT_TOTAL',
(SELECT COUNT(*) FROM B) as 'NEW_EMPLOYEES',
(SELECT COUNT(*) FROM C) as 'NEW_SALARIED'
FROM A
WHERE rowcount = 1;
Now if I want to make this into PL/SQL with variables that are passed in or predefined at the top, it's not a simple matter of declaring the variables, popping values into them, and changing my hard-coded values into variables and running it. NOTE: I do know that I can simply change the hard-coded values to variables like :Department, :StartDate, and :Type, but again, I am oversimplifying the example.
There are three issues I am facing here that I am trying to wrap my head around:
1) What would be the best way to rewrite this using PL/SQL with declared variables? The CTEs now have to go INTO something. But then I am dealing with one row at a time as opposed to the entire table. So CTE 'A' is a single row at a time, and CTE B will only see the single row as opposed to all of the data results of A, etc. I do know that I will most likely have to use CURSORS to traverse the records, which somehow seems to over complicate this.
2) The output now has to use DBMS_OUTPUT. For multiple records, I will have to use a CURSOR with FETCH (or a FOR...LOOP). Yes?
3) Is there going to a big performance issue with this vs. straight SQL in regards to speed and resources used?
Thanks in advance and again, my apologies if I am missing something really obvious here!
First, this has nothing to do with CTEs. This behavior would be the same with a simple select * from table query. The difference is that with T-SQL, the query goes into an implicit cursor which is returned to the caller. When executing the SP from Management Studio this is convenient. The result set appears in the data window as if we had executed the query directly. But this is actually non-standard behavior. Oracle has the more standard behavior which might be stated as "the result set of any query that isn't directed into a cursor must be directed to variables." When directed into variables, then the query must return only one row.
To duplicate the behavior of T-SQL, you just have to explicitly declare and return the cursor. Then the calling code fetches from the cursor the entire result set but one row at a time. You don't get the convenience of Sql Developer or PL/SQL Developer diverting the result set to the data display window, but you can't have everything.
However, as we don't generally write SPs just to be called from the IDE, it is easier to work with Oracle's explicit cursors than SQL Server's implicit ones. Just google "oracle return ref cursor to caller" to get a whole lot of good material.
Simplest way is to wrap it into an implicit for loop
begin
for i in (select object_id, object_name
from user_objects
where rownum = 1) loop
-- Do something with the resultset
dbms_output.put_line (i.object_id || ' ' || i.object_name);
end loop;
end;
Single row query without the need to predefine the variables.
With TSQL I'm used to putting some repeatable tests in for my stored procs. Typically this may include putting the db in a particular state, runnings the sproc, validating the state and rolling back. And contrived example might something like this"
BEGIN TRAN
--input for test case
DECLARE #TestName VARCHAR(10) = 'bob'
--insert test row
INSERT INTO tbl (data) values (#TestName)
--display initial state of target row
SELECT * FROM tbl WHERE data = #TestName
--do some useful test
EXEC MyProc
--display the final state of the target row
SELECT * FROM tbl WHERE data = #TestName
--put the db back where it started
ROLLBACK TRAN
Now I'm working with Oracle and PL/SQL and I'm trying to use a some similar pattern to test my work and not finding it obvious to me quite how to do that. I believe there are a few different ways I might accomplish it but haven't gotten anything to actually work. Ideally I would have a single script in which I could run multiple test cases and inspect the result.
I am trying to work in PL/SQL Developer at this point and understand that might have some differences from how it might work in Oracle SQL Developer or elsewhere.
In Oracle, using tools like SQL*Plus and GUI tools like SQL Developer, you have many options :
To execute the statements and procedures in a single session in an order, i.e. using procedural method of PL/SQL, write an anonymous plsql block and execute it as a script.
Most of the GUI based tools have an option like Execute as script or Test Window to execute your scripts individually or embedded in an anonymous block.
Using DBMS_SCHEDULER also you could achieve the same task.
As you are interested in PL/SQL Developer tool product of Allround Automations, you could simply use the test window to test individual objects.
I have documented few useful features of the PL/SQL Developer tool in my blog, please read http://lalitkumarb.wordpress.com/2014/08/14/plsql-developer-settings/
I'm running a query across a database link to a Sybase server from Oracle.
In it's where clause is a restriction on date, and I want it tied to sysdate, so something like this:
select * from some_remote_view where some_numeric_key = 1 and
some_date > sysdate+2
The problem is, when I do explain plan, only the condition some_numeric_key = 1 shows up in the actual sql that is getting remoted to the sybase server. Oracle is expecting to perform the date filter on its side.
This is causing a performance nightmare - I need that date filter remoted across to have this query working quickly
Even if I try something like casting the sysdate to a charcater string like this:
to_char(sysdate-2,'YYYY-MM-DD')
It still does not remote it.
Is there anything I can do to get Oracle to remote this date filter across the db link to Sybase?
Doing integration between Oracle and other platforms I often run into this problem, not just with SYSDATE but with other non-standard functions as well.
There are two methods to work around the issue, the first being the most reliable in my experience.
First, you can create a view on the remote db with the filters you need, then on the Oracle side you just select from the new view without additional filters.
Second, if you are not allowed to create objects on the remote side, try using bind variables (of the correct data type!) in your Oracle SELECT statement, e.g.:
declare
v_some_date constant date := sysdate + 2;
begin
insert into oracle_table (...)
select ...
from remote_table#db_link t
where t.some_numeric_key = 1
and t.some_date > v_some_date;
commit;
end;
/
Can anybody let me know if there is any way to find out cost of a stored procedure in Oracle? If no direct way is there, I would like to know any substitutes.
The way I found the cost is doing an auto trace of all the queries used in the stored procedure and then estimate the proc cost according to the frequency of the queries execution.
In addition to that I would like suggestions to optimize my stored procedure especially the query given below.
Logic of the procedure:
Below is the dynamic sql query used as a cursor in my stored procedure. This cursor is opened and fetched inside a loop. I fetch the info and put them in a varray, count the data and then insert it to a table.
My objective is to find out the cost of the proc as well as optimize the sp.
SELECT DISTINCT acct_no
FROM raw
WHERE 1=1
AND code = ''' || code ||
''' AND qty < 0
AND acct_no
IN (SELECT acct_no FROM ' || table_name || ' WHERE counter =
(SELECT MAX(counter) FROM ' || table_name || '))
One of the best tool in analyzing SQL and PLSQL performance is the native SQL trace.
enable tracing in your session:
SQL> alter session set SQL_TRACE=TRUE;
Session altered
Run your procedure
Exit your session
Navigate to your server udump directory and find your trace file (usually the latest)
Run tkprof
This will produce a file containing a list of all statements with lots of information, including the number of times each was executed, its query plan and statistics. This is more detailed and precise than manually running the plan for each select.
If you want to optimize performance on a procedure, you would usually sort the trace file by the time taken to execute (with sort=EXEELA) or fetch SQL and try to optimize the queries that make the most work.
You can also make the trace file log wait events by using the following command at step 1:
ALTER SESSION SET EVENTS '10046 trace name context forever, level 8';
The way to find out the cost (in execution of time) for a stored procedure is to employ a profiler. 11g introduced the Hierarchical Profiler which is highly neat. Find out more.
Prior to 11g there was only the DBMS_PROFILER, which is good enough, especially if your stored procedure doesn't use objects in other schemas. Find out more.
Trace is good for identifying poorly performing SQL. Profilers are good for identifying the cost of the PL/SQL elements of a stored proc. If your proc has some expensive computation elements which don't read or write to tables then that won't show up in SQL trace.
Likewise if you have a well-tuned SQL statement but use it badly ia profiler run is likely to be more help than trace. An example of what I mean is repeatedly executing the same SELECT statement inside a Cursor loop: I know that's not quite what you're doing but it's close enough.
Apparently the hierarchical profiler DBMS_HPROF is installed by default in 11g but a DBA has to grant some privileges to developers who want to use it. Find out more.
To install the DBMS_PROFILER in 10g (or earlier) a DBA has to run this script:
$ORACLE_HOME/rdbms/admin/proftab.sql
Be sure to get the reporting infrastructure as well:
$ORACLE_HOME/plsql/demo/profsum.sql
(The name or location of this script may vary in earlier versions).
The easy way is to execute the procedure and then query v$sql.
if you want a little tip to make your life easier (not just for packages) add a blank comment to the query inside the procedure, something like
select /* BIG DADDY */ * from dual;
and then query v$sql as follows
select * from v$sql where sql_text like '%BIG DADDY%';
the best way is definitely the way #Vincent Malgrat suggested.
good luck.
I have a stored procedure that consists of a single select query used to insert into another table based on some minor math that is done to the arguments in the procedure. Can I generate the plan used for this query by referencing the procedure somehow, or do I have to copy and paste the query and create bind variables for the input parameters?
Use SQL Trace and TKPROF. For example, open SQL*Plus, and then issue the following code:-
alter session set tracefile_identifier = 'something-unique'
alter session set sql_trace = true;
alter session set events '10046 trace name context forever, level 8';
select 'right-before-my-sp' from dual;
exec your_stored_procedure
alter session set sql_trace = false;
Once this has been done, go look in your database's UDUMP directory for a TRC file with "something-unique" in the filename. Format this TRC file with TKPROF, and then open the formatted file and search for the string "right-before-my-sp". The SQL command issued by your stored procedure should be shortly after this section, and immediately under that SQL statement will be the plan for the SQL statement.
Edit: For the purposes of full disclosure, I should thank all those who gave me answers on this thread last week that helped me learn how to do this.
From what I understand, this was done on purpose. The idea is that individual queries within the procedure are considered separately by the optimizer, so EXPLAIN PLAN doesn't make sense against a stored proc, which could contain multiple queries/statements.
The current answer is NO, you can't run it against a proc, and you must run it against the individual statements themselves. Tricky when you have variables and calculations, but that's the way it is.
Many tools, such as Toad or SQL Developer, will prompt you for the bind variable values when you execute an explain plan. You would have to do so manually in SQL*Plus or other tools.
You could also turn on SQL tracing and execute the stored procedure, then retrieve the explain plan from the trace file.
Be careful that you do not just retrieve the explain plan for the SELECT statement. The presence of the INSERT clause can change the optimizer goal from first rows to all rows.