Article ID: 62460
Article Last Modified on 8/16/2005
APPLIES TO
- Microsoft BASIC Professional Development System 7.0
- Microsoft BASIC Professional Development System 7.1
This article was previously published under Q62460
SYMPTOMS
When you specify a unique key with CREATEINDEX using Microsoft Basic Professional Development System (PDS) version 7.00 ISAM, inserting records with duplicate keys causes a trappable error (run-time error 86). However, the ISAM engine still inserts one record into the ISAM file per attempt to insert a duplicate key record. The records inserted with the duplicate keys are marked as deleted. The Basic function LOF, which returns the total number of records in a Basic PDS 7.00 ISAM file, will show the actual number of successful writes to the file, showing that the records written with duplicate keys are not valid. Since these records are marked as deleted, using the ISAMPACK utility will remove the records and reduce the file to its appropriate size.
STATUS
Microsoft has confirmed this to be a bug in Microsoft Basic Professional Development System (PDS) versions 7.00 and 7.10 for MS-DOS. We are researching this problem and will post new information here as it becomes available.
MORE INFORMATION
The sample program below demonstrates the problem. If you execute the code below, a record will be inserted into the ISAM file, and then 999 more attempts will be made to insert that record. Since the program specifies unique keys in the CREATEINDEX statement, run-time error 86, "Duplicate key," will occur. The program will trap the "Duplicate key" error and resume execution. When the program terminates, the LOF function will show there is only one legitimate record in the file. The file size, however, will be approximately 1.6 MB. Using ISAMPACK.EXE on the ISAM file created by the program will reduce the file to 64K in size.
To execute the program below, you must load the Basic PDS 7.00 or 7.10 ISAM support by executing the PROISAMD.EXE TSR (terminate-and-stay- resident) program. After PROISAMD has been loaded, you can execute the program within the QBX.EXE environment.
Code Example
'WARNING: Even though this program only successfully
' writes one ISAM record, it creates a 1.6 MB file.
TYPE NewRec
AString AS STRING * 8
END TYPE
40 ON ERROR GOTO errorhandler
50 DIM NewBuf AS NewRec
60 OPEN "output.mdb" FOR ISAM NewRec "NewRec" AS #1
70 CREATEINDEX #1, "X", 1, "AString" '* Specify unique key *
80 NewBuf.AString = "ABCDEFGH"
90 FOR i = 1 TO 1000
100 INSERT #1, NewBuf '* Causes 999 "Duplicate key" errors *
110 PRINT i
120 NEXT
130 PRINT "Size of database (should be 1): "; LOF(1)
135 DELETEINDEX #1, "X" ' Delete the index so the program
' can be run over.
140 END
errorhandler:
150 SELECT CASE ERR
CASE 86: PRINT "duplicate key attempted":
RESUME NEXT
CASE ELSE
CLS
PRINT "An error occurred. The number is: "; ERR
PRINT "It occurred on line: "; ERL
DELETEINDEX #1, "X"
END
END SELECT
Additional query words: BasicCom buglist7.00 buglist7.10
Keywords: KB62460
