[SOLVED] Laz 2.0.10/fpc 3.2.0 and TBufDataset
lazarus / 16-Databases

----------------------------------------------------------------------
OH1KH · 2021-03-02 09:46

HI !

Can someone again kindly advice me of reading (and understanding) the
changes file. Thank you.

I see that Lazarus 2.0.12 is out, but it seems the fpc part has not
changed (file names and zip sizes are same)
I will test that later when I have time so I assume the error still
exist.

Now the problem is with  TBufDataset.

Code that perfectly works with laz2.0.8/fpc 3.0.4 does not work any
more causing access violation error.
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i db :=
TBufDataset.Create(nil);        try          db.FieldDefs.Clear;     
   with db.FieldDefs do          begin            Add('loc', ftString,
4);            Add('cfm',ftBoolean)          end;         
db.CreateDataset;         
db.IndexDefs.Add('loc','loc',[ixPrimary]);           db.Open;        
wkd := 0;          while not dmData.Q1.Eof do          begin         
 db.Append;            db.Fields[0].AsString  :=
dmData.Q1.Fields[0].AsString;            db.Fields[1].AsBoolean :=
False;            db.Post;            inc(wkd);           
dmData.Q1.Next          end;       
When execution comes  first time to line dp.post Access violation
error is created.

I tried to find what would be the difference reading changes documents
but I could not find (understand) any reason.

----------------------------------------------------------------------
LacaK · 2021-03-02 09:58

if you omit line 10 : db.IndexDefs.Add('loc','loc',[ixPrimary]);
then there is still AV ?

----------------------------------------------------------------------
dseligo · 2021-03-02 10:35

Quote from: LacaK on March 02, 2021, 10:58:00 amif you omit line 10 :
db.IndexDefs.Add('loc','loc',[ixPrimary]);
then there is still AV ?
I also had this problem with IndexDefs.Add (and I just commented it
out).
After "Open" I added:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
IndexFieldNames:='myfield1;myfield2';
I don't know if that helps.

----------------------------------------------------------------------
OH1KH · 2021-03-02 11:18

Thanks for quick reply!

Yes!
Commenting out line  db.IndexDefs.Add('loc','loc',[ixPrimary]); helps.

This part of code is not originally written by me so I have to clear
out what IndexDefs.Add there stands for and could/needs this to be
replaced with IndexFieldNames:='myfield1;myfield2';
Program seems to work without IndexFieldNames and with it. With quick
look result is similar.

Funny that this it again one problem that arises when you update
laz/fpc without touching the source you are going to compile.
And in this case I could not find anything from update changes file
that I am able to connect to this problem.

----------------------------------------------------------------------
PascalDragon · 2021-03-02 12:42

Quote from: OH1KH on March 02, 2021, 12:18:58 pmYes!
Commenting out line  db.IndexDefs.Add('loc','loc',[ixPrimary]); helps.
You should use TCustomBufDataset.AddIndex instead. IndexDef should be
considered as readonly.

----------------------------------------------------------------------
cdbc · 2021-03-02 13:18

Code: [Select]Hi
Try this:

[code=pascal]
Procedure TBufDataset.CopyFromDataset(DataSet : TDataSet; CopyData :
Boolean);
Var
  I  : Integer;
  F,F1,F2 : TField;
  L1,L2  : TList;
  N : String;
begin
  Clear(True);
  // NOT from fielddefs. The data may not be available in buffers !!
  for I:= 0 to Dataset.FieldCount-1 do begin
    F:= Dataset.Fields[I];
    // ææ special case for ftAutoInc fields 16.02.2020 /bc
    if F.DataType = ftAutoInc then TFieldDef.Create(FieldDefs,F.FieldN
ame,ftInteger,F.Size,F.Required,F.FieldNo)
    else TFieldDef.Create(FieldDefs,F.FieldName,F.DataType,F.Size,F.Re
quired,F.FieldNo);
  end;
  CreateTable;
  if CopyData then begin
    Open;
    L1:= TList.Create;
    try
      L2:= TList.Create;
      try
        for I:= 0 to FieldDefs.Count-1 do begin
          N:= FieldDefs[I].Name;
          F1:= FieldByName(N);
          F2:= DataSet.FieldByName(N);
          L1.Add(F1);
          L2.Add(F2);
        end;
        Dataset.DisableControls;
        try
          Dataset.Open;
          while not Dataset.EOF do begin
            Append;
            for I:= 0 to L1.Count-1 do begin
              F1:= TField(L1[i]);
              F2:= TField(L2[I]);
              case F1.DataType of
                ftString   : F1.AsString:= F2.AsString;
                ftBoolean  : F1.AsBoolean:= F2.AsBoolean;
                ftFloat    : F1.AsFloat:= F2.AsFloat;
                ftLargeInt : F1.AsInteger:= F2.AsInteger;
                ftSmallInt : F1.AsInteger:= F2.AsInteger;
                ftInteger  : F1.AsInteger:= F2.AsInteger;
                ftDate     : F1.AsDateTime:= F2.AsDateTime;
                ftTime     : F1.AsDateTime:= F2.AsDateTime;
                ftDateTime : F1.AsDateTime:= F2.AsDateTime;
              end;
            end;
            try Post; except Cancel; Raise; end;
            Dataset.Next;
          end;
        finally Dataset.EnableControls; end;
      finally L2.Free; end;
    finally L1.Free; end;
  end;
end;
Implement this in TBufDatset and maybe locate, I dono.
Indexes i dono 
As you can see it's 'stolen' from TMemDataset.

Regards Benny

----------------------------------------------------------------------
OH1KH · 2021-03-02 13:42

Change code like this makes it work:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    db :=
TBufDataset.Create(nil);         try          db.FieldDefs.Clear;    
    //with db.FieldDefs do          //begin           
db.FieldDefs.Add('loc', ftString, 4);           
db.IndexDefs.Add('loc','loc',[ixPrimary]);           
db.FieldDefs.Add('cfm',ftBoolean);          //end;         
db.CreateDataset;         
//db.IndexDefs.Add('loc','loc',[ixPrimary]);          db.Open;       
 wkd := 0;          while not dmData.Q1.Eof do          begin        
  db.Append;            db.Fields[0].AsUTF8String  :=
dmData.Q1.Fields[0].AsString;            db.Fields[1].AsBoolean :=
False;            db.Post;            inc(wkd);           
dmData.Q1.Next          end;                 
IndexDefs should be done before CreateDataset, then no error happen in
db.post any more.