Mutating Trigger Error
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Mutating Trigger In Oracle 10g With Example
Users Badges Unanswered Ask Question _ Database Administrators Stack Exchange is a question and answer site for database professionals who wish to mutating trigger with example improve their database skills and learn from others in the community. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted oracle mutating trigger pragma autonomous transaction up and rise to the top What are the causes and solutions for mutating table errors? up vote 7 down vote favorite 1 I understand mutating table errors are caused by a design flaw or problematic query. An old query was recently put into production which throws a mutating table error. Our DBA solved the problem but we do not know how. What exactly causes mutating table errors and how would our DBA have fixed
Statement Level Trigger In Oracle
the problem? sql oracle trigger plsql share|improve this question edited Jun 25 '15 at 17:56 Mahi_0707 1033 asked Sep 6 '11 at 8:46 parmanand 112238 add a comment| 3 Answers 3 active oldest votes up vote 13 down vote accepted The most likely cause of a mutating table error is the misuse of triggers. Here is a typical example: you insert a row in table A a trigger on table A (for each row) executes a query on table A, for example to compute a summary column Oracle throws an ORA-04091: table A is mutating, trigger/function may not see it This is an expected and normal behaviour, Oracle wants to protect you from yourself since Oracle guarantees: (i) that each statement is atomic (i.e will either fail or succeed completely) (ii) that each statement sees a consistent view of the data Most likely when you write this kind of trigger you would expect the query (2) to see the row inserted on (1). This would be in contradiction with both points above since the update is not finished yet (there could be more rows to be inserted). Oracle could return the result consistent with a point in time just before the beginning of the statement but from most of the examples I have seen that try to implement this logic, people see
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Ora-04091 Solution
from within row-level trigger code. In this article I'll present examples of how a mutating table exception might occur and simple methods to get round it. Test Schema Mutating Table http://dba.stackexchange.com/questions/5432/what-are-the-causes-and-solutions-for-mutating-table-errors Demonstration Solution 1 (Collection in Package Variable) Solution 2 (Global Temporary Table) Test Schema The following schema objects are necessary to run the code in this article. CREATE TABLE tab1 ( id NUMBER(10) NOT NULL, description VARCHAR2(50) NOT NULL ); ALTER TABLE tab1 ADD ( CONSTRAINT tab1_pk PRIMARY KEY (id) ); CREATE SEQUENCE tab1_seq; CREATE TABLE tab1_audit ( id https://oracle-base.com/articles/9i/mutating-table-exceptions NUMBER(10) NOT NULL, action VARCHAR2(10) NOT NULL, tab1_id NUMBER(10), record_count NUMBER(10), created_time TIMESTAMP ); ALTER TABLE tab1_audit ADD ( CONSTRAINT tab1_audit_pk PRIMARY KEY (id) ); ALTER TABLE tab1_audit ADD ( CONSTRAINT tab1_audit_tab1_fk FOREIGN KEY (tab1_id) REFERENCES tab1(id) ); CREATE SEQUENCE tab1_audit_seq; Mutating Table Demonstration Let's assume we need to audit the actions on the parent table and for some reason, this involves querying the triggering table. We can demonstrate this with the following package and trigger. We place all our trigger code into a package as follows. CREATE OR REPLACE PACKAGE trigger_api AS PROCEDURE tab1_row_change (p_id IN tab1.id%TYPE, p_action IN VARCHAR2); END trigger_api; / SHOW ERRORS CREATE OR REPLACE PACKAGE BODY trigger_api AS PROCEDURE tab1_row_change (p_id IN tab1.id%TYPE, p_action IN VARCHAR2) IS l_count NUMBER(10) := 0; BEGIN SELECT COUNT(*) INTO l_count FROM tab1; INSERT INTO tab1_audit (id, action, tab1_id, record_count, created_time) VALUES (tab1_audit_seq.NEXTVAL, p_action, p_id, l_count, SYSTIMESTAMP); END tab1_row_change; END trigger_api; / SHOW ERRORS Next we create the row-level trigger itself to catch any changes to the table. CREATE OR REPLACE TRIGGER tab1_ariu_trg AFTER INSERT OR UPDATE
- 8:40 pm UTC Category: SQL*Plus � Version: 8.1.7 Latest Followup You Asked hello, i've got a table MRC and a trigger on it (AFTER INSERT) thus, after an insert in the table MRC, this trigger has to determine if a new line must be inserted into https://asktom.oracle.com/pls/apex/f?p=100:11:0%3A%3A%3A%3AP11_QUESTION_ID:9579487119866 an other table PLAN : for that, it does compare the :new values with the MOST http://www.akadia.com/services/ora_mutating_table_problems.html RECENT enregistrement of MRC but i got a mutating table error i understand the problem but how can i get over ?? thanks Arnaud and we said... My personal opinion -- when I hit a mutating table error, I've got a serious fatal flaw in my logic. Have you considered the multi-user implications in your logic? Two people inserting at the same time mutating trigger (about the same time). What happens then??? Neither will see eachothers work, neither will block -- both will think "ah hah, I am first"... anyway, you can do too much work in triggers, this may well be that time -- there is nothing wrong with doing things in a more straightforward fashion (eg: using a stored procedure to implement your transaction) but if you persist, you can use the technique: http://asktom.oracle.com/~tkyte/Mutate/index.html to avoid the mutating table constraint -- trigger in oracle but I would avoid the situation that gets me there in the first place. The logic is a whole lot more understandable that way (and maintainable and testable and everything) Reviews Write a Review Ora-4091 May 05, 2003 - 5:45 pm UTC Reviewer: A reader We create trigger in the test server (8i) its working without error, and when we created at life (8) we get the following error: ORA-04091: table XXXX is mutating, trigger/function may not see it. Followup May 05, 2003 - 8:31 pm UTC they relaxed some of the constraining rules between 8.0 and 8.1 -- things are in general upwards (develop in 8.0 and goto 8.1) compatible but not backwards. Why I can't get the 4091 error when insert? January 05, 2004 - 3:39 am UTC Reviewer: Li ys from CHINA I only want to prove the mutating table by this triggers: CREATE TABLE r_Module ( Bureauno NUMBER(3), Moduleno NUMBER(3), primary key ( Bureauno, Moduleno ) ); CREATE OR REPLACE TRIGGER LimitTest BEFORE INSERT OR UPDATE ON r_Module FOR EACH ROW DECLARE v_MaxModuleNum CONSTANT NUMBER := 5; v_CurModuleNum NUMBER; BEGIN SELECT COUNT(*) INTO v_CurModuleNum FROM r_Module WHERE Bureauno = :new.Bureauno; IF v_CurModuleNum + 1 > v_MaxModuleNum THEN RAISE_APPLICATION_ERROR(-20000,'Too many Module in the Bureauno:'||:new.Bureauno); END IF; END; / When I insert some record into r_module table,I can't get the 4091 error,but when I update one, the error come. I wonder if the insert can't lead
4 ORA-04088: error during execution of trigger 'TRG_GET_ID_APP'. We studied the "Mutating Table" Problem and found the following explanations in the Oracle8i Application Developer's Guide. A mutating table is a table that is currently being modified by an UPDATE, DELETE, or INSERT statement, or it is a table that might need to be updated by the effects of a declarative DELETE CASCADE referential integrity constraint. The restrictions on such a table apply only to the session that issued the statement in progress. For all row triggers, that were fired as the result of a DELETE CASCADE, there are two important restrictions regarding mutating tables. These restrictions prevent a trigger from seeing an inconsistent set of data. The SQL statements of a trigger cannot read from (query) or modify a mutating table of the triggering statement. Example 1 Select in a mutating table from a row trigger (Tested on Oracle 8.1.7) We want to explain this situation on an example. We have two tables "A" and "B". "A" is the master table and "B" the detail table. We specified a foreign key between "B" and "A" with the CASCADE DELETE option. Here are the CREATE statements drop table B; drop table A; create table A ( ida number not null, vala varchar2(10), primary key(ida)); create table B ( idb number, valb varchar2(10), foreign key (idb) references A (ida) on delete cascade) / create or replace trigger b_br after delete on B for each row declare n integer; begin select count(*) into n from A; dbms_output.put_line('there are ' || n || ' rows in A'); dbms_output.put_line('after statment on B'); dbms_output.new_line; end; / insert into A values(1,'Table A'); insert into A values(2,'Table A'); insert into B values(1,'Table B'); insert into B values(1,'Table B'); commit; set serveroutput on; delete from A where idA = 1; ERROR at line 1: ORA-04091: table SCOTT.A is mutating, trigger/function may not see ORA-06512: at "SCOTT.B_BR", line 4 ORA-04088: error during execution of trigger 'SCOTT.B_BR' Notice that the SQL statement ( "select count(*) into n from A" ) is run for the first row of the table, and then the AFTER row trigger B_BR is fired. In turn, a statement in the AFTER row trigger body attempts to query the original table A. However, because the table A is