FIX: Using RI Builder & Long Table Names Makes Triggers Fail

• Microsoft Visual FoxPro for Windows, versions 3.0 and 3.0b

SYMPTOMS

Using the RI Builder's code along with tables that have long table names and Private datasessions results in triggers constantly failing. The underlying error causing the triggers to fail is Error 1 "File <file_name> does not exist."

CAUSE

There are two causes. First the SET DATABASE command is scoped to Private Datasessions. Thus, there is no Database current and the appropriate database must be current for Visual FoxPro to be able to resolve long table names. Second, the Referential Integrity (RI) Builder does not take this previous issue into account.

WORKAROUND

Modify the RIOPEN procedure the RI Builder created. The modifications would consist of finding the Database the table with the long table name belongs to, using CURSORGETPROP(), SET DATABASE to this Database. Let the RIOPEN routine open the table. Then use SET DATABASE to set the database back to the original database if any.

Example Workaround

To work around this problem, make the following modifications to the RIOPEN Procedure:

1. Copy the entire RIOPEN procedure, and paste it below the "__RI_FOOTER"

2. Add the following variables to the copied RIOPEN's LOCAL declarations:

   __lcCurDBC, __tcOldTable

3. Insert the following lines immediately after the copied RIOPEN's LOCAL declarations:

   && Replace any spaces in Long Table name with "_". && because this is what VFP does in the DE, Aliases && are not allowed to contain spaces. __tcOldTable=tcTable tcTable=STRTRAN(ALLTRIM(tcTable)," ","_")

   && Find the DBC name the Table belongs to __lcCurDBC=SET('DATABASE') &&Get any current DBC __lcDBCName=CURSORGETPROP('DATABASE',tcTable) && Get Database Name

   __lcDBCName=substr(__lcDBCName,rat('\',__lcDBCName)+1) &&Remove path __lcDBCName=substr(__lcDBCName,1,rat('.',__lcDBCName)-1) &&Remove '.DBC'

   SET DATABASE TO (__lcDBCName)

   && Restore original value, the USE needs the actual Long Table name tcTable=__tcOldTable

4. Insert the following line immediately after the first ENDIF of the copied RIOPEN procedure:

   && Set back to original DBC SET DATABASE TO &__lcCurDBC

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem has been fixed in Visual FoxPro 5.0 for Windows.

MORE INFORMATION

Steps to Reproduce Problem

1. Create a new database with a Parent Child Persistent Relation, and give the parent table a long table name.

2. Set the RI Builder so that there is RESTRICT on the Child table's Insert.

3. Create a new form, and add both tables to its Data Environment.

4. Set the Child Cursors's BuffermodeOverride property to 5.

5. Set the form's DataSession property to 2-Private Datasession.

6. Add the child table's Foreign Key to the Form.

7. Add a Command button to the form. Set its Caption property to Add, and Add the following code to its Click event:

   SELECT <child table> APPEND BLANK THISFORM.REFRESH

8. Add another Command button to the form. Set its caption property to Save, and add the following code to its Click event:

   SELECT<child table> IF .NOT. TABLEUPDATE(.T.,.T.)

         =TABLEREVERT(.T.) &&Revert the change
         IF TYPE('gaErrors[1,1]') <> 'L'
            =MESSAGEBOX('Trigger Failed - '+gaErrors[1,2],0,;
              'Data Entry Error/Trigger Failed')
         ENDIF
         GO TOP
      ENDIF
      THISFORM.REFRESH
   
   

9. Run the form. Click the Add button, and type in a value that is not in the Parent's Primary Key. Click the "Save" button.