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Q135562: FIX: Delete Trigger Fires Out of Order

Article: Q135562
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbbuglist kbfixlist
Last Modified: 24-MAR-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SYMPTOMS
========

The Delete trigger fires immediately when buffering level is 2-Record
(Pessimistic) or 3-Record (Optimistic).

CAUSE
=====

With these buffering levels, the Delete trigger should fire when you leave a
record. However, it fires immediately as though the buffering level was 1 (Off -
No Buffering).

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article. This problem was corrected in Visual FoxPro 3.0b
for Windows.

MORE INFORMATION
================

Rules and triggers are there to protect the integrity of the data. The order in
which the rules and triggers fire depends directly on the buffering in effect at
that time. With Buffering levels 2 or 3, the Delete trigger should not fire
until you attempt to leave the record instead of immediately because that record
is buffered until you move the record pointer off that record.

Steps to Set Up Example to Reproduce Problem
--------------------------------------------

1. To duplicate the behavior of the firing order of rules and triggers, create
  the following sample database and table with the specified stored procedures.
  Enter the following in the Command window:

     CREATE DATABASE Mydata      && Creates the database container
     MODIFY DATABASE Mydata      && Opens the database container

2. Enter the following procedures into the Stored Procedures:

     PROCEDURE MYDEL
     =MESSAGEBOX("My Delete Trigger")

3. Enter the following in the Command window:

     CREATE TABLE Mytab(Fname C(15),Lname C(15))
     CREATE TRIGGER ON Mytab FOR DELETE AS Mydel()

Steps to Reproduce Problem
--------------------------

1. In the Command window, type:

     OPEN DATABASE Mydata
     SET MULTILOCKS ON         && Required for buffering.
     =CURSORSETPROP("Buffering",1)   && Turns Buffering Off

  Or on the Tools menu, click Options. In the Data tab, set Buffering to Off

2. To verify the setting, enter the following on a new line in the Command
  window:

     ? CURSORGETPROP("Buffering")

  This will return the value of the Buffering level: 1=Off,
  2=Record(Pessimistic), 3=Record(Optimistic), 4=Table(Pessimistic), and
  5=Table(Optimistic).

3. Select the title bar of the table, click the secondary (right) mouse button,
  and choose Browse.

4. With Table Buffering set Off, press CTRL+Y to append a blank record.

5. Mark any record for deletion. The Delete trigger fires immediately. This is
  correct behavior when Buffering is level 1 - Off.

6. Enter the following commands in the Command window:

        SET MULTILOCKS ON      && If you have not done so previously.
        =CURSORSETPROP("Buffering",2)

  Or on the Tools menu, click Options. Then in the Data tab, set Buffering to
  2-Record (Pessimistic). If no data exists, press CTRL+Y to append a blank
  record.

7. Mark any record for deletion, the Delete trigger fires immediately. This is
  incorrect behavior when Buffering is level 2 or 3.

8. Change Buffering to 4 (Pessimistic Table Locks) by typing in the following
  Command window:

        SET MULTILOCKS ON      && If you have not done so previously.
        =CURSORSETPROP("Buffering",4)   && Table(Pessimistic)

  Or on the Tools menu, click Options. Then in the Data tab, set Buffering to
  4-Table (Pessimistic). If no data exists, press CTRL+Y to append a blank
  record. Then do the following:

  a. If no entries exist, press CTRL+Y to append a blank record. Enter at least
     2 records.

  b. Mark any record for deletion. The Delete trigger doesn't fire immediately.
     This is correct behavior. Changes to the table have been buffered, so they
     are not be written until a Tableupdate is issued.

  c. Type the following in the Command window: =TABLEUPDATE(.t.) Now the Delete
     trigger fires as the table is updated from the buffer. The same correct
     behavior occurs for buffering level 5.

9. Change the buffering level to 1 (Off) by typing in the following Command
  window:

  =CURSORSETPROP("Buffering",1)

  Or on the Tools menu, click Options. Then in the Data tab, set Buffering to 1
  (Off). Then you can pack or recycle the records.

Additional query words: 3.00 VFoxWin fixlist3.00b buglist3.00 events

======================================================================
Keywords          :  kbbuglist kbfixlist
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0
Issue type        : kbbug
Solution Type     : kbfix

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