Jason,

Thanks, but yes I did try bsmReadWrite. Using bsmWrite in the example code was a typo because I tried that too.

bsmReadWrite results in the exact same behavior: stream of size 0.

Then, even more, running the same routine twice and trying to .Post the changes in the middle part (where I try to rewrite the beginning of the stream with the buffer) I now get an error "Record was not located to update."

See below for latest code.

Any new ideas?

Marko


procedure TForm1.Button5Click(Sender: TObject);
var
Buff : array of byte;
F : TField;
St : TIB_BlobStream;
I : integer;
begin
SetLength (Buff, 10);
for I := 0 to 10 do Buff [I] := I;

IB_Query1.SQL.Text := 'select * from curvey where rown = 2';
IB_Query1.Open;
St := TIB_BlobStream (IB_Query1.CreateBlobStream (IB_Query1.FieldByName ('datax'), bsmRead));
ShowMessage (IntToStr (St.Size)); // => Result in "0" on the first round, "10" on the second
St.Free;

IB_Query1.Close;
IB_QUery1.RequestLive := true;
IB_Query1.Open;
IB_Query1.Edit;

St := TIB_BlobStream.CreateForColumn (IB_Query1.FieldByName ('datax'), bsmReadWrite);

ShowMessage (IntToStr (St.Size)); // => Result in "0"
St.Seek (0, soFromBeginning);
St.WriteBuffer (Buff [0], 10);
ShowMessage (IntToStr (St.Size)); // => Results in "10"
IB_Query1.Post; // Error here on 2nd round
St.Free;

IB_Query1.Close;
IB_QUery1.RequestLive := true;
IB_Query1.Open;
IB_Query1.Edit;

St := TIB_BlobStream (IB_Query1.CreateBlobStream (IB_Query1.FieldByName ('datax'), bsmReadWrite));
ShowMessage (IntToStr (St.Size)); // => Results in "0"
St.Seek (0, soFromEnd);
ShowMessage (IntToStr (St.Position)); // => Results in "0" even though there is data

St.WriteBuffer (Buff [0], 10);
IB_Query1.Post;
St.Free;
end;

--- In IBObjects@yahoogroups.com, "IBO Support List" <supportlist@...> wrote:
>
> bmWrite clears out previous information.
>
> Did you try bmReadWrite?
>
> Jason
>
> -----Original Message-----
> From: IBObjects@yahoogroups.com [mailto:IBObjects@yahoogroups.com] On Behalf
> Of mjmyllym
> Sent: 07 November 2012 08:32 AM
> To: IBObjects@yahoogroups.com
> Subject: [IBO] No way to append to BLOBs using CreateBlobStream
>
> Hello,
>
> I have a critical problem in appending data to binary BLOBs using
> CreateBlobStream.
>
> I am using IBO4_9_14_b52, Delphi 6. Tried both Firebird 2.1 and 2.0;
> different BLOB types etc.
>
> The thing is I can read from a BLOB and write to a BLOB but cannot append.
> Opening a BLOB with existing data with CreateBlobStream in
> bsmWrite/bsmReadWrite mdoe always results in a stream of size 0! So I cannot
> seek the stream and append to the end. If I look at the query's data in
> string format I can see the existing data but not in Stream format.
>
> Very simple database:
>
> create table curves (
> rown integer,
> datax blob sub_type 0,
> primary key (rown));
>
> Then, I have a form with TIBODatabase, IBOQuery or IB_Query (neither works),
> and a simple test that first reads from a BLOB (ok), then writes a simple
> array of byte data to a BLOB (ok) and finally tries to append to it =>
> fails.
>
> procedure TForm1.Button5Click(Sender: TObject);
> var
> Buff : array of byte;
> F : TField;
> St : TIB_BlobStream;
> I : integer;
> begin
> SetLength (Buff, 10);
> for I := 0 to 10 do Buff [I] := I;
>
> // First read from the BLOB, might be empty
> IB_Query1.SQL.Text := 'select * from curves where rown = 1';
> IB_Query1.Open;
> St := TIB_BlobStream (IB_Query1.CreateBlobStream (IB_Query1.FieldByName
> ('datax'), bsmRead));
> ShowMessage (IntToStr (St.Size)); // => Result in "0" on the first
> round, "10" on the second
> St.Free;
>
> // Then write to:
> IB_Query1.Close;
> IB_QUery1.RequestLive := true;
> IB_Query1.Open;
> IB_Query1.Edit;
>
> St := TIB_BlobStream (IB_Query1.CreateBlobStream (IB_Query1.FieldByName
> ('datax'), bsmReadWrite));
> ShowMessage (IntToStr (St.Size)); // => Result in "0"
>
> St.WriteBuffer (Buff [0], 10);
> ShowMessage (IntToStr (St.Size)); // => Results in "10", as it
> should
> IB_Query1.Post;
> St.Free;
>
> // Now let's try to append:
> IB_Query1.Close;
> IB_QUery1.RequestLive := true;
> IB_Query1.Open;
> IB_Query1.Edit;
>
> St := TIB_BlobStream (IB_Query1.CreateBlobStream (IB_Query1.FieldByName
> ('datax'), bsmWrite));
> ShowMessage (IntToStr (St.Size)); // => Results in "0".. like there
> is no data!
>
> St.WriteBuffer (Buff [0], 10);
> IB_Query1.Post;
> St.Free;
> end;
>
>
> Frustrating.
>
> I CAN append to the blob if I use e.g.
>
> St := TMemoryStream.Create;
> TBlobField (F).SaveToStream (St);
> ...
> St.WriteBuffer (Data, Length);
> TBlobField (F).LoadFromStream (St);
>
> but this is very ineffective because I need to write to the BLOBs all the
> time, i.e. several times a minute. Also this results in a huge database
> bloating.
>
> Thank you in advance for help.
>
> Best regards,
> Marko Myllymaki
>
>
>
>
> ------------------------------------
>
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