TAstaServerSocket.OnFetchMetaData

Applies to
TAstaServerSocket

Declaration
type TAstaServerMetaDataEvent = procedure(Sender: TObject;
  ClientSocket: TCustomWinSocket; MetaRequest: TAstaMetaData;
  DataBaseStr, Arg1, Arg2: string) of object;

Description
ASTA clients require information about the server database, and coding the OnFetchMetaData event is required for ASTA clients to be able to fetch tablenames, fieldnames, index information, foreign key information, stored procedure names and columns and other assorted server database information. AstaClientDataSets trigger this server side event using their MetaDataRequest property.

The OnFetchMetaData event is currently NOT threaded and will return the AstaServerSocket.MetaDataSet to ASTA clients.

The following is an abridged version of the OnFetchMetaData event as coded on the AstaBDEServer. An important point is that whatever request that comes in from the client, the MetaData property is set on the TAstaServerSocket so that the correct information is streamed back to ASTA clients. The AstaBDEServer uses the ASTA component AstaBDEInfoTable to retrieve BDE information and the AstaODBCInfoDataSet to retrieve meta data information using components from www.odbcexpress.com. Source is available for these two ASTA units on request from ASTA registered users.

procedure TForm1.AstaServerSocket1FetchMetaData(Sender: TObject;
  ClientSocket: TCustomWinSocket; MetaRequest: TAstaMetaData;
  DataBaseStr, Arg1, Arg2: string);

var

  i: Integer;

begin

  try

    case MetaRequest of

      mdIndexes, mdPrimeKeys, mdForeignKeys:

        begin

          LogIt('Index Info for ' + Arg1);

          IndexInfoTable.Close;

          IndexInfoTable.TableName := Trim(Arg1);

          AdjustBDEInfoDatabaseName(DataBaseStr, IndexInfoTable);

          IndexInfoTable.Active := True;

          if AstaDataSet1.Active then AstaDataSet1.Empty;

          AstaDataSet1.CloneFieldsFromDataSet(IndexInfoTable,
            False, False);

          IndexDataTransfer(IndexInfoTable, AstaDataSet1);

          AstaServerSocket1.MetaDataSet := AstaDataSet1;

        end;

      mdStoredProcColumns:

        begin

          //ODBC and the BDE create different column names and types.

          //When returning param info the BDEInfoToStoredProcAstaInfoTable

          //call uses a standard datadet (AstaStoredProcColumnDataSet)

          //that the ASTA client.SQLWorkbench can use.

          //Other backends need to populate the fields in

          //AstaStoredProcColumnDataSet

          TableDataSet.Close;

          TableDataSet.BDEInfo := BDEStoredProcParams;

          AdjustBDEInfoDatabaseName(DataBaseStr, TableDataSet);

          TableDataSet.TableName := Arg1;

          TableDataSet.Open;

          BDEInfoToStoredProcAstaInfoTable(TableDataSet,

            AstaStoredProcColumnDataSet);

          AstaServerSocket1.MetaDataSet :=

            AstaStoredProcColumnDataSet;

          LogIt('Stored Proc Param Info for ' + Arg1);

        end;

      mdStoredProcs:

        begin

          {$ifdef StoredProcProblemo}

          PopulateStoredProcNames;

          {$else}

          AstaServerSocket1.MetaDataSet := TableDataSet;

          TableDataSet.Close;

          TableDataSet.BDEInfo := BDEStoredProcedures;

          AdjustBDEInfoDatabaseName(DataBaseStr, TableDataSet);

          TableDataSet.TableName := '';

          TableDataSet.Open;

          {$endif}

          LogIt('Stored Procedure List');

        end;

      mdDBMSName:

        begin

          LogIt('DBMS Info Request');

          AstaServerSocket1.MetaDataSet := DBMSDataSet;

        end;

      mdServerDataSets:

        begin

          LogIt('Server DataSet Info Request');

          AstaServerSocket1.MetaDataSet := ServerDataSets;

        end;

    else begin

      LogIt('Table Info');

      TableDataSet.Close;

      AdjustBDEInfoDatabaseName(DataBaseStr, TableDataSet);

      TableDataSet.TableName := '';

      TableDataSet.BDEInfo := BDEOpenTables;

      TableDataSet.Open;

      AstaServerSocket1.MetaDataSet := TableDataSet;

    end;

  except

    LogException(ClientSocket, 'Stored MetaData Error: ' +

      EDataBaseError(ExceptObject).Message, True);

  end;

end;