Oracle-L: Re: Foreign key indexes on individual columns or multiple columns

From: MURAT BALKAS <murat.balkas_at_o2.net.tr>
Date: Tue, 14 Jan 2003 03:58:51 -0800
Message-ID: <F001.0052EE54.20030114035851@fatcity.com>

Hi,

following script may help you. The brief description of the script is as follows.

REM This file checks the current users Foreign Keys to make sure of the REM following:
REM
REM 1) All the FK columns are have indexes to prevent a possible locking REM problem that can slow down the database. REM
REM 2) Checks the ORDER OF THE INDEXED COLUMNS. To prevent the locking

REM       problem the columns MUST be index in the same order as the FK is
REM       defined.

REM
REM 3) If the script finds and miss match the script reports the correct

REM       order of columns that need to be added to prevent the locking
REM       problem.

REM
REM
REM
REM

(See attached file: foreign_key_locks.sql)

                                                                                                                                                     
                      "Krishnaswamy, Ranganath"                                                                                                      
                      <Ranganath.Krishnaswamy_at_blr.hps        To:       Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>                   
                      global.com>                            cc:                                                                                     
                      Sent by: root_at_fatcity.com              Subject:  Foreign key indexes on individual columns or multiple columns                 
                                                                                                                                                     
                                                                                                                                                     
                      01/14/2003 12:29 PM                                                                                                            
                      Please respond to ORACLE-L

Hi List,

I have a table by name Benchmark_hdr with the following columns:

  BENCHMARK_HDR_ID    NUMBER        NOT NULL
  CALENDAR_TYPE     CHAR (1),
  UOM               VARCHAR2 (10),
  CALENDAR_PORT     CHAR (1),
  CUSTOMER_MOT_ID   NUMBER        NOT NULL
  RESP_PARTY_NAME   VARCHAR2 (10),
  FROM_EVENT        NUMBER,
  TO_EVENT          NUMBER,
  LAST_UPDATED      DATE

I have created foreign key constraints using the below commands:

  ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHAMRK_HDR_CUSTOMERESP_FK FOREIGN KEY (RESP_PARTY_NAME, CUSTOMER_MOT_ID)   REFERENCES XM.CUSTOMER_RESPONSIBLE_PARTY (RESP_PARTY_NAME, CUSTOMER_MOT_ID) ; ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHAMRK_HDR_CUSTOMEREVENT_FK FOREIGN KEY (FROM_EVENT)
  REFERENCES XM.CUSTOMER_EVENT (CUSTOMER_EVENT_ID) ON DELETE CASCADE; ALTER TABLE BENCHMARK_HDR ADD CONSTRAINT BENCHMARK_HDR_CUSTOMEREVENT_FK FOREIGN KEY (TO_EVENT)
  REFERENCES XM.CUSTOMER_EVENT (CUSTOMER_EVENT_ID) ON DELETE CASCADE;   The foreign keys need to be indexed so that the child table is not locked when a record in the parent table is being updated or deleted. If the foreign keys are indexed the corresponding child record or records are only locked when the parent table record is being updated or deleted. In this context I would like to seek the advice of the list as to whether I should create indexes on individual foreign keys or should I create one or more composite index(es) on foreign keys? If I need to create a composite index on which columns should I base my index on? Could anybody advise me on this
with the reasons for following that particular approach? Any help in this regard is very much appreciated.

Thanks and Regards,

Ranganath

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-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: MURAT BALKAS INET: murat.balkas_at_o2.net.tr Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L
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application/octet-stream attachment: foreign_key_locks.sql

Received on Tue Jan 14 2003 - 05:58:51 CST