problems with IBCQuery and blob fields?

[Bjarke_Moholt]

I am experiencing changed behaviour with blob fields after porting from BDE to IBC.
I've tested a bit and find that blob fields appear to be written differently in IBC than they were in BDE.

I'm wondering if there are any known issues - and hopefully solutions - to this?

[ViktorV]

Please describe the problem in more details. Try to compose a small sample to demonstrate the problem and send it to viktorv*devart*com.

[Bjarke_Moholt]

OK, this might be a bit long so I'll start with the abstract:
I have a question. Is there a property on the IBCQuery that may affect the size of the blob when it is written/read?


I have some problems reproducing my problem in an isolated project. I have a suspicion of where things go wrong though and have a question that may clear things up

This is what I do:

Code: Select all

   
   MS := TMemoryStream.Create;
   MS.LoadFromFile('e:\Shares\bjarke.moeholt\MemoryStream');

    MS.Position := 0;
    IBCQuery.SQL.LoadFromFile('e:\Shares\bjarke.moeholt\skydatvalSQL');
    //INSERT INTO @SomeTable@([Index],[BLOBVAL])
    //VALUES( :Index,:BlobVal )
    IBCQuery.Params[0].asInteger := 1;
    IBCQuery.Params[1].SetBlobData( MS.Memory, MS.Size );
    IBCQuery.ExecSQL;

    //read it back
    Q.SQL.Clear;
    Q.SQL.Add('SELECT * FROM SomeTable');
    Q.Open;
    Q.First;

    FileBlobs := IBCQuery.FieldByName('BLOBVAL') as TBlobField;
    Stream:=IBCQuery.CreateBlobStream(FileBlobs,bmRead);
    ValSize := 4; //sizeof(single)
    NumVal := Trunc(Stream.Size/ValSize); //Stream.Size is double the expected!!
    setLength(resultSIArray, NumVal);
    Stream.ReadBuffer(pointer(resultSIArray)^, NumVal * ValSize);

The symptom of the problem is that Stream.size returns a value twice as big as the expected value (the value we saw in MS.size, the size of the written blob), and the contents of the blob are not consistent with the values I put in
By testing with BDE as a reference I have established that the problem is in the write section, However as I said earlier I cannot reproduce the problem in an isolated case.
Now my question comes up: Is there a property on the IBCQuery that may affect the size of the blob when it is written/read?

[ViktorV]

Unfortunately, we can't reproduce the issue in the way you have described it. The Stream.size value is equal to the MS.size value. You can ensure this by executing the following code:

Code: Select all

program TestBlob;

{$APPTYPE CONSOLE}

uses
  System.SysUtils, IBC, System.Classes, Data.DB;

var
  IBCConnection: TIBCConnection;
  IBCQuery: TIBCQuery;
  MS: TMemoryStream;
  Stream : TStream;
  FileBlobs: TField;

begin
  IBCConnection := TIBCConnection.Create(nil);
  try
    IBCConnection.Server := Server;
    IBCConnection.Port := Port;
    IBCConnection.Database := NEW_TEST_DATABASE;
    IBCConnection.ClientLibrary := ClientLibrary;
    IBCConnection.Username := 'sysdba';
    IBCConnection.Password := 'masterkey';
    IBCConnection.Params.Clear;
    IBCConnection.Params.Add('USER ''SYSDBA''');
    IBCConnection.Params.Add('PASSWORD ''masterkey''');
    IBCConnection.Params.Add('PAGE_SIZE 4096');
    IBCConnection.Params.Add('DEFAULT CHARACTER SET WIN1251');

    try
      IBCConnection.Connect;
      IBCConnection.DropDatabase;
    except
    end;

    IBCConnection.CreateDatabase;
    IBCConnection.ExecSQL('CREATE TABLE Test_BLOB (ID INTEGER, F_BLOB BLOB)');
    WriteLn('Create Ok');

    IBCQuery := TIBCQuery.Create(nil);
      try
        IBCQuery.Connection := IBCConnection;
        MS := TMemoryStream.Create;
        MS.LoadFromFile('d:\ofs.txt');
        MS.Position := 0;
        IBCQuery.SQL.Text := 'INSERT INTO TEST_BLOB (ID, F_BLOB) VALUES( :ID,:F_BLOB)';
        IBCQuery.Params[0].asInteger := 1;
        IBCQuery.Params[1].SetBlobData( MS.Memory, MS.Size );
        IBCQuery.ExecSQL;
        WriteLn('MS.Size = ' + IntToStr(MS.Size));

        IBCQuery.SQL.Text := 'SELECT * FROM TEST_BLOB';
        IBCQuery.Open;

        FileBlobs := IBCQuery.FieldByName('F_BLOB') as TBlobField;
        Stream:=IBCQuery.CreateBlobStream(FileBlobs, bmRead);
        WriteLn('Stream.Size = ' + IntToStr(Stream.Size));
      finally
        IBCConnection.Disconnect;
        IBCQuery.Free;
      end;

    ReadLn;

  finally
    IBCConnection.Free;
  end;
end.

[Bjarke_Moholt]

Yes, I get the same result in an isolated project. I am now trying to ensure that the relevant environment variables are the identical in the two projects..
Does the IBCQuery have a property that may influence the perceived size of an incoming/outgoing stream?

(Edit) Just saw the lines regarding charset and pagesize, will try with these

[ViktorV]

IBCQuery has no property that may influence the perceived size of an incoming/outgoing stream.