How to locate unindexed foreign keys

Two issues can be avoided if you index your foreign key columns:

  • Slow joins (Full Table Scans) between parent/child tables
  • Deadlocks when updating or deleting a parent key.

The following script is very helpfull in locating unindexed foreign keys:

column columns format a20 word_wrapped
column table_name format a30 word_wrapped

select decode( b.table_name, NULL, '****', 'ok' ) Status,
 a.table_name, a.columns, b.columns
from
( select substr(a.table_name,1,30) table_name,
substr(a.constraint_name,1,30) constraint_name,
   max(decode(position, 1,     substr(column_name,1,30),NULL)) ||
   max(decode(position, 2,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 3,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 4,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 5,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 6,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 7,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 8,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position, 9,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,10,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,11,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,12,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,13,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,14,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,15,', '||substr(column_name,1,30),NULL)) ||
   max(decode(position,16,', '||substr(column_name,1,30),NULL)) columns
 from user_cons_columns a, user_constraints b
where a.constraint_name = b.constraint_name
  and b.constraint_type = 'R'
group by substr(a.table_name,1,30), substr(a.constraint_name,1,30) ) a,
( select substr(table_name,1,30) table_name, substr(index_name,1,30) index_name,
   max(decode(column_position, 1,     substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 2,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 3,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 4,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 5,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 6,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 7,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 8,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position, 9,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,10,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,11,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,12,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,13,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,14,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,15,', '||substr(column_name,1,30),NULL)) ||
   max(decode(column_position,16,', '||substr(column_name,1,30),NULL)) columns
 from user_ind_columns
group by substr(table_name,1,30), substr(index_name,1,30) ) b
where a.table_name = b.table_name (+)
and b.columns (+) like a.columns || '%'
/

Comments

Post a Comment

Popular posts from this blog

ORA-00923: FROM keyword not found where expected

Problem Symptom While performing a simple select statement it fails with error ORA-00923: FROM keyword not found where expected like below. SQL> select 48*1024*1024*1024 decimal from dual; select 48*1024*1024*1024 decimal from dual * ERROR at line 1: ORA-00923: FROM keyword not found where expected Cause of the problem The ORA-00923 can be caused by two different reasons. 1)Oracle itself expect FROM keyword in the position but it could not find any. Like below, SQL> select 48*1024 om dual; select 48*1024 om dual * ERROR at line 1: ORA-00923: FROM keyword not found where expected As no from keyword found so error arises. Oracle expected from in place of keyword dual. 2)The secong cause can sometimes mislead you. Like in case of SQL> select 48*1024*1024*1024 decimal from dual; select 48*1024*1024*1024 decimal from dual * ERROR at line 1: ORA-00923: FROM keyword not found where exp
Read more

How to make partitioning in Oracle more Quickly

As the table size grows and full table scans happens more frequently then there is no alternative than partitioning in oracle. Partition greatly enhance performance of a query. I will start my partitioning system simply with an example. In my database the following query took 30~35 seconds to complete. After partitioning the performance increased amazingly and it then took only 1 second. My query was, SELECT DISTINCT fs.type, fs.id , fs.pid, fs.cid , fs.cr_id, fs.created_date FROM summary fs where fs.id in (select fa.id from forms fa where fa.sar in (select la.sar from login la where la.login_id=1 and fa.created_date BETWEEN to_date('1-MAY-2008') AND to_date('21-SEP-2008') and fs.created_date BETWEEN to_date('1-MAY-2008') AND to_date('21-SEP-2008') ) )and mode=0; After seeing above query I decide to make range partition on column created_date both in summary table and forms table. Below is the list of procedur
Read more

Copy files between Unix and Windows with rcp

There are many third party tools by which you can copy files between windows and unix machine. Some common tools are winscp, SSHSecureShellClient etc. Instead of using any third party tool, you can use original unix and windows built-in tool to do the task. The RCP (Remote CoPy) is a standard UNIX tool and a Microsoft Windows 2000 tool that copies files/folder to and from computer running the RCP service. Before you can use the RCP tool from a Windows-based computer you must do something in your UNIX computer. you must turn on the RCP service and update the security files to allow the Windows-based computer to connect to your unix machine over this service. The following steps will help you. Step 01: Turn on RCP service on UNIX Host Turn on the RCP service on unix machine by using inetd: 1. Log on as root. 2. Edit the file /etc/Inetd.conf. 3. Uncomment the lines that start with shell and that start with exec. 4. Save the file. 5. Use ps -ef |grep inetd and determine inetd service p
Read more