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IndexFile missing Dbase

Posted on 1998-05-19
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Last Modified: 2013-11-24
Hi,

How can I open or add indexes to a Dbase IV table when the Indexfile (*.MDX)
is missing. With Database desktop it is possible to open such a table, so I
expect that there is BDE function to do this. I want to make a tool that
opens such tables and restores the indexes.

I tried with Table.open, dbiopentable and Table.addindex but I get always
the message index does not exist.

I am using Delphi 1.0

All help is appreciated

Regards Didier,
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Question by:Didier
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Accepted Solution

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jhunt earned 70 total points
ID: 1346210
What you basicly have to do is:
Examine if byte 28 in the header of the DBase file is set to 1. If so the BDE expects a production index. If the index file is not there then you will have to change byte 28 of the header from 1 to 0.

This is what does the trick:
TDBFHeader = record
 ID: byte;
 LastUpdate: array[1..3] of byte;
 LastRec: integer;
 DataOffset: word;
 RecordSize: word;
 Filler1: array[1..16] of byte;
 StructIDX: boolean;
 Filler2: array[1..3] of byte;
end;

in the beforeopen event of your table:
procedure TCodeTable.DoBeforeOpen;
var      filename, extension: string;
      DBF: TFileStream; Dbase: TDatabase;
      Header: TDBFHeader;
begin
 DBase := Session.FindDatabase ( Databasename );
 extension := ExtractFileExt(TableName);
 if not DBase.IsSQLBased and
     ( (CompareText(extension, '.DBF') = 0) or (TableType=ttDBase) )
 then begin
  filename := DBase.Directory + Tablename;
  if Empty(extension)then begin
   extension := '.DBF';
   filename := filename + '.DBF';
  end;
  if FileExists(Filename) then begin
        DBF := TFileStream.Create(Filename, fmOpenReadWrite + fmShareDenyNone);
  try
  DBF.Read(Header, SizeOf(Header));
  if Header.StructIDX then begin
  Filename := Copy(Filename, 1, Length(Filename) - Length(Extension));
  if TableLevel = 25
  then filename := filename + '.CDX'
  else filename := filename + '.MDX';
  if not FileExists(Filename) then begin
   Header.StructIDX := false;
   DBF.Seek (0, soFromBeginning);
   DBF.Write(Header, SizeOf(Header));
 end;
 end;              
finally
DBF.Free;
end;
end;
end;


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