Get Schema and Data in one call

Data Abstract
1

We have a Server developed in Delphi and an ASP.Net client

Server side

// Here the SQL is completely build dynamically, there is no other way!!
// The dataset.SQL is filled and the dataset is opened.

DataStreamer.WriteDataset(Result, dataSet, [woRows, woSchema], -1);

Client Side

DataSet ds = new DataSet();
DataStreamer Streamer = new BinDataStreamer();

        RemoteService RORemoteService = new RemoteService();
        RORemoteService.ServiceName = "HDSUserDataBroker";
        RORemoteService.Message = BinMessageFactory.CreateMessage();
        RORemoteService.Channel = ChannelFactory.CreateChannel();

        RemoteDataAdapter DAAdapter = new RemoteDataAdapter();
        DAAdapter.RemoteService = RORemoteService;
        DAAdapter.DataStreamer = Streamer;

        DAAdapter.SchemaCall.MethodName = "GetLookupDataSet";

        DAAdapter.SchemaCall.Parameters.Clear();
        DAAdapter.SchemaCall.Parameters.Add("Result", "Binary", RemObjects.SDK.ParameterDirection.Result);
        DAAdapter.SchemaCall.Parameters.Add("UsersessionId", "WideString", ParameterDirection.In);
        DAAdapter.SchemaCall.Parameters.Add("LookupFieldSeq", "Integer", ParameterDirection.In);
        DAAdapter.SchemaCall.Parameters.Add("LookupTableFilterSeq", "Int64", ParameterDirection.In);
        DAAdapter.SchemaCall.Parameters.Add("ParentKeyValue", "Int64", ParameterDirection.In);

        DAAdapter.SchemaCall.Parameters.ParameterByName("UsersessionId").Value = UsersessionId;
        DAAdapter.SchemaCall.Parameters.ParameterByName("LookupFieldSeq").Value = FieldSeq;
        DAAdapter.SchemaCall.Parameters.ParameterByName("LookupTableFilterSeq").Value = lookupTableFilterSeq;
        DAAdapter.SchemaCall.Parameters.ParameterByName("ParentKeyValue").Value = ParentKeyValue;

        DAAdapter.DataRequestCall.MethodName = "GetLookupDataSet";

        DAAdapter.DataRequestCall.Parameters.Clear();
        DAAdapter.DataRequestCall.Parameters.Add("Result", "Binary", RemObjects.SDK.ParameterDirection.Result);
        DAAdapter.DataRequestCall.Parameters.Add("UsersessionId", "WideString", ParameterDirection.In);
        DAAdapter.DataRequestCall.Parameters.Add("LookupFieldSeq", "Integer", ParameterDirection.In);
        DAAdapter.DataRequestCall.Parameters.Add("LookupTableFilterSeq", "Int64", ParameterDirection.In);
        DAAdapter.DataRequestCall.Parameters.Add("ParentKeyValue", "Int64", ParameterDirection.In);

        DAAdapter.DataRequestCall.IncomingDataParameter = "Result";

        DAAdapter.DataRequestCall.Parameters.ParameterByName("UsersessionId").Value = UsersessionId;
        DAAdapter.DataRequestCall.Parameters.ParameterByName("LookupFieldSeq").Value = FieldSeq;
        DAAdapter.DataRequestCall.Parameters.ParameterByName("LookupTableFilterSeq").Value = lookupTableFilterSeq;
        DAAdapter.DataRequestCall.Parameters.ParameterByName("ParentKeyValue").Value = ParentKeyValue;

        string[] saString = new string[1];
        saString[0] = lookupTableName;
        DAAdapter.DataRequestCall.Parameters.Add("aTableNameArray", "StringArray", RemObjects.SDK.ParameterDirection.In);
        DAAdapter.DataRequestCall.Parameters.ParameterByName("aTableNameArray").Value = saString;
        DAAdapter.DataRequestCall.OutgoingTableNamesParameter = "aTableNameArray";

        ds.Tables.Add(lookupTableName);
        try
        {
            ---> DAAdapter.FillSchema(ds, saString);
            ---> DAAdapter.Fill(ds, true);
        }
        catch
        {
            throw;      // Reraise exception to get clear message
        }

        return ds.Tables[0];

The two calls from the client side (DAAdapter.FillSchema and DAAdapter.Fill) both result in a complete dataset being sent to the client, which is not what we want (performance).
Can we use just a single call on the client side???

regards
Paul Sjoerdsma

2

Hello Paul.

As you use custom method (GetLookupDataSet method) to get data then you can return both table Schema and data as a result of this method and then use this result on the client side.

Hope this helps.

3

Hi Andreyt,

We are returning both data and schema in one call from the server:

DataStreamer.WriteDataset(Result, dataSet, [woRows, woSchema], -1);

However I am unclear which call to use on the client side to get both schema and data in once call. At the moment we are using two calls:

DAAdapter.FillSchema(ds, saString);
DAAdapter.Fill(ds, true);

There must be a single call I can make to replace these two calls, not sure which one though??

regards
Paul

4

I figured it out, calling
DAAdapter.Fill(ds, true);
will load the schema as well so that’s teh call to use

5

Hello Paul.

On the client side you can use Fill method as follows:

       DAAdapter.Fill(newdataset,true); << true value allows to fill Schema together with data. This request uses one call.

after this it is possible to use Schema as follows:

  var schema = fDataModule.DataAdapter.Schema;

Getter method for Schema property is ReadSchema method that recall schema information if Schema==null or ForceReRead property is true. So, in this case client will use only one call to server side.

Hope this helps.