FIX: An additional EOF character is inserted by using SELECT-SQL within a transaction in Visual FoxPro for Windows (221624)



The information in this article applies to:

  • Microsoft Visual FoxPro for Windows 5.0
  • Microsoft Visual FoxPro for Windows 5.0a
  • Microsoft Visual FoxPro for Windows 6.0

This article was previously published under Q221624

SYMPTOMS

You have an application that updates a record in a table, which is buffered, and the TABLEUPDATE() call is made within a transaction. This application also executes a SELECT-SQL statement against the same table within the transaction. Another application or program running within a separate instance of Visual FoxPro then adds a record or records to the same table before the first instance has committed the changes. When the transaction is written from the first instance, an extra end of file (EOF) character, ASCII value 26, is written to the table.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

MORE INFORMATION

Steps to Reproduce Behavior

  1. Start an instance of Visual FoxPro. Run the following code from a program file:
    SET EXCLUSIVE OFF
       CLEAR
       CLOSE DATA ALL
       CREATE DATABASE testdb
    
       CREATE TABLE testtab1 (F1 C(10) NOT NULL ;
          PRIMARY KEY, ;
          F2 C(10) NOT NULL)
       FOR lnj = 1 TO 10
          INSERT INTO testtab1 (F1) VALUES (PADL(ALLTR(STR(lnj)),10,'0'))
       ENDFOR
    
       CLOSE DATA ALL
    
       USE testtab1
       SET MULTILOCKS ON
       =CURSORSETPROP('buffering',5)
       GO BOTTOM
       REPLACE F2 WITH (SYS(2015))
       ?"Before BEGIN TRANS, Estimated - actual length =",TestTable()
       SUSPEND
    
       BEGIN TRANS
       SELECT * FROM testtab1 INTO CURSOR ctemp NOFILTER
       SELECT testtab1
       =TABLEUPDATE(.T.)
       ?"Within TRANS, Estimated - actual length =",TestTable()
       END TRANS
       =INKEY(1)
       ?"After END TRANS, Estimated - actual length =",TestTable()
       CLOSE DATA ALL
       * Read DBF into a string variable. Could FILETOSTR() in VFP 6.0.
       CREATE CURSOR ctemp (m1 m)
       APPEND BLANK
       APPEND MEMO m1 FROM testtab1.DBF
       lcLast2 = SUBSTR(m1, LEN(m1)-1)  && Return last 2 characters
       USE
    
       * Report ASCII value of last 2 characters.
       ?"Next to last char ASCII value =",ASC(SUBSTR(lcLast2,1,1))
       ?"Last char ASCII value =",ASC(SUBSTR(lcLast2,2,1))
    
       PROC TestTable()
          LOCAL lnEstSize, lnActualSize
          SET COMPATIBLE ON
          * lnEstSize = Header size + (record length*record count) + 1
          * The + 1 represents the end of file character, CHR(26)
    
          lnEstSize = HEADER() +RECSIZE()* RECCOUNT() + 1
          * The actual file size
          lnActualSize = FSIZE(DBF())
          SET COMPATIBLE OFF
          RETURN lnEstSize - lnActualSize
       ENDPROC
    						
  2. Start another instance of Visual FoxPro. Set this instance to the same default directory as used in the instance of Visual FoxPro opened in step 1. Run the following code from a program file:
    SET EXCLUSIVE OFF
    USE testtab1
    SELECT testtab1
    APPEND BLANK
    REPLACE f1 WITH (PADL(ALLTR(STR(RECNO())),10,'0'))
    CLOSE DATA ALL
    						
  3. ALT+TAB back to the first instance, then from the Program menu choose Resume. The estimated file size will be one byte less than the actual file size. The last 2 characters are both ASCII 26, or the end of file marker. There is one extra end of file character, as there should only be a single EOF character.

NOTE: When the table is located on a network drive, the extra character may not result in the actual table file size differing from the estimated size.

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Jim Saunders, Microsoft Corporation.


Modification Type:MajorLast Reviewed:3/11/2005
Keywords:kbBug kbDatabase kbfix kbSQLProg kbVS600sp3fix KB221624