Query Performance

Do you know columns in selection list affect use of index on table..??

I couldn't  believe this..I was always under impression that query plan is decided based on from and where clause and select clause has no impact on index usage. I was proved wrong in the Smoke Test for INT2 at midnight yesterday..

See how...

select trx_number, org_id, interface_header_attribute1      
          from ra_customer_trx_all
          where org_id = 112 
         
Plan
SELECT STATEMENT  ALL_ROWSCost: 1,947  Bytes: 219,538  Cardinality: 9,979     
    1 TABLE ACCESS FULL TABLE AR.RA_CUSTOMER_TRX_ALL Cost: 1,947  Bytes: 219,538  Cardinality: 9,979 



select trx_number, org_id      
          from ra_customer_trx_all
          where org_id = 112
         
Plan
SELECT STATEMENT  ALL_ROWSCost: 551  Bytes: 129,727  Cardinality: 9,979     
    1 INDEX SKIP SCAN INDEX AR.RA_CUSTOMER_TRX_N1 Cost: 551  Bytes: 129,727  Cardinality: 9,979 
        
Ultimately the solution to this performance issue was add one more table to query... Interesting huh?

bad query
select trx_number
          from ra_customer_trx_all
          where 1=1
          and interface_header_attribute1 = to_char(pin_order_number)
          and org_id = v_Header_Rec_Type.org_id
          and rownum = 1;

Good query

select trx_number      
          from apps.ra_customer_trx_all rct, apps.ra_customer_trx_lines_all rctl
          where rct.customer_trx_id = rctl.customer_trX_id
            and rctl.sales_order = to_char(66000120)
            and rct.org_id = 112
            and rownum < 2;

Materialized View with Fast Refresh idea

Complete refresh for materialized views may not be time effective in all cases. Moreover if the changes to data are minimal Fast refresh should be used and scheduled frequently using cron job or dbms_job.

I faced issue as there was no primary key on underlying table to create materialized view. I was under impression that there must be primary key. However there is an idea to beat this..

We can create materialized view based on rowid column as well

Below are the scripts

---------------- on Web DB  -------------------

create materialized view log on subscription.xxrh_subscription with rowid excluding new values;

grant select on subscription.MLOG$_xxrh_subscription to web;



----------------- On R12EBS environment in Web Schema  ---------------

CREATE MATERIALIZED VIEW web.xxrh_subscription_mv tablespace web_data
    REFRESH FAST ON DEMAND WITH ROWID AS
    SELECT *
    FROM subscription.xxrh_subscription@WEB_LINK;

CREATE INDEX web.XXRH_SUBSCRIPTION_MV_IDX1 ON web.XXRH_SUBSCRIPTION_MV(ORACLE_ACCOUNT_NUMBER) tablespace web_indx;

ThanksAnil Prodduturi for this knowledge!

ORA-04021 Timeout when compiling package

Sometimes we face timeout error ORA-04021 when trying to compile existing package.

Following steps can help to get rid of the error.
1) Find who is accessing the object using below sql
     SELECT * FROM v$access WHERE object = 'XXRH_SUPX_ORCL_PKG';

2) Check session details using below query. SID will be from the result of above query
    SELECT * FROM V$SESSION WHERE SID IN (1040,1529,1016)

3) Kill the session which is accessing the package . Ensure that you inform osuser of these session before you kill them!
   ALTER SYSTEM KILL SESSION '1016,58335'

Go ahead with package compilation!