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dbase 'Pack'

Posted on 1997-03-21
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How do you 'pack' a dbase file in VB3 (or 4 for that matter). I have deleted loads of records and wish to reclaim the space.      
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Question by:hughm
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dirkmartin earned 70 total points
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Here you go....


To be able to ZAP or PACK your .DBF files, you must have the following entry in your VB.INI or <appname>.INI file:

   [dBase ISAM]
   Deleted=On

This will filter out deleted records so they do not appear in recordsets.

To perform a ZAP, you simply need to run a DELETE action query. For example, the following sample marks all the records in the AUTHORS.DBF table as deleted:

   Dim db As database
   Set db = OpenDatabase("c:\dBaseIII", false, false, "dBase III")
   'Open the database.

   db.Execute "Delete From Authors"       'Execute the delete action query.
   db.Close                               'Close the database.

For extremely large tables, it is more efficient to delete the Tabledef representing the table from the TableDefs collection of the database and then re-create the table structure.

The following subroutine shows you how to perform a PACK. Essentially, you copy all the records to a new temporary table, delete the old one, then rename the temporary table as the original name.

Sample Code

   Sub Pack_DBF (db As Database, tblname As String)
     Const MB_YESNO = 4                     ' Yes and No buttons
     Const MB_ICONEXCLAMATION = 48          ' Warning message
     Const IDYES = 6                        ' Yes button pressed

     Dim dbdir As String, tmp As String 'Temp variables
     Dim i As Integer, ret As Integer   'Counter and return value of MsgBox

     Dim flags As Integer                   'Flags for MsgBox
     ReDim idxs(0) As New index             'Holds indexes

     On Error GoTo PackErr

     flags = MB_YESNO Or MB_ICONEXCLAMATION
     ret = MsgBox("Remove All Deleted Records in " & tblname & "?", flags)
     If ret = IDYES Then
       dbdir = db.Name + "\"                      'Hold database directory

       'Delete the temp file if it exists.
       If Dir$(dbdir & "p_a_c_k.*") <> "" Then
         Kill dbdir & "p_a_c_k.*"
       End If

       'Store the indexes.
       For i = 0 To db.TableDefs(tblname).Indexes.Count - 1
         ReDim Preserve idxs(i + 1)
         idxs(i).Name = db.TableDefs(tblname).Indexes(i).Name
         idxs(i).Fields = db.TableDefs(tblname).Indexes(i).Fields
         idxs(i).Primary = db.TableDefs(tblname).Indexes(i).Primary
         idxs(i).Unique = db.TableDefs(tblname).Indexes(i).Unique
       Next

       'Create the new table without the deleted records.
       db.Execute "Select * into [p_a_c_k] from " & tblname

       'Delete the current table.
       db.TableDefs.Delete tblname

       'Rename the DBF file and any memo files.
       tmp = Dir$(dbdir & "p_a_c_k.*")
       Do While tmp <> ""
       'Rename with the correct file extension; this should be on one line.

           Name dbdir & tmp As dbdir & tblname &
                                Right$(tmp, Len(tmp) - InStr(tmp, ".") + 1)
           tmp = Dir$
       Loop

       'Refresh the tabledefs and add the indexes to the new table.
       db.TableDefs.Refresh
       For i = 0 To UBound(idxs) - 1
         db.TableDefs(tblname).Indexes.Append idxs(i)
       Next

       MsgBox "'" & tblname & "' successfully Packed!", MB_ICONEXCLAMATION
     End If
     Exit Sub

   PackErr:
     MsgBox Error$
     Exit Sub

   PackEnd:
   End Sub

The following example code shows you how to call the above subroutine. First, you open the database the table is in, then you pass the database object and the name of the table to PACK to the subroutine. Be sure that there are not any open recordsets on the table you are trying to pack or you will get an error.

   'To open file C:\SAMPLES\FOXTBL.DBF
   Dim db As Database
   Set db = OpenDatabase("c:\samples\foxtbl", False, False, "foxpro 2.5")
   Call Pack_DBF(db, "foxtbl")
   db.Close

The above methods do not preserve formatting of numeric fields for our dBASE and FoxPro tables. To work around this limitation you should keep a template DBF file created from dBASE or FoxPro that contains the formatting you need, and use an INSERT INTO statement instead of the SELECT INTO statement shown above.
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