MySQL Bugs: #40371: Triggerfunction can't use table where the trigger occured

Bug #40371	Triggerfunction can't use table where the trigger occured
Submitted:	28 Oct 2008 14:08	Modified:	15 Dec 2010 10:30
Reporter:	Frank Mussmann	Email Updates:
Status:	Duplicate	Impact on me:	None
Category:	MySQL Server	Severity:	S4 (Feature request)
Version:	5.0	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	stored procedure, trigger

Description:
As mentioned in F.1. Restrictions on Stored Routines and Triggers
"Within a stored function or trigger, it is not permitted to modify a table that is already being used (for reading or writing) by the statement that invoked the function or trigger."
But this would be a good detail for working with triggers.
When I got a Table "wtf" like this:
n   int     <-- PK
ttt varchar(200)
ttt2 varchar(10) and ttt2 represents left(ttt,10), it would be great to have a trigger like this:
CREATE TRIGGER t_insert_after 
FOR EACH ROW BEGIN
 update wtf set ttt2=left(ttt) where n=NEW.n;
END

This would be great for big bulk inserts.

How to repeat:
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Suggested fix:
Within a stored function or trigger, it is not permitted to modify a table that is already being used (for reading or writing) by the statement that invoked the function or trigger.
BUT:
Updates are OK when Inserting/Updates on other fields which are invoked by the Trigger-function
NO UPDATES while DELETE !!!

This is a duplicate of bug #29542.