Question

I have visual fox pro database with thousands of rows. I am using oledb to fetch data from fox pro and export(after doing some calculation and fomatting) it to sql server.I have used dataset to populate 2-3 datatable(related table) at a time.

First problem is that the memory use is very high because the dataset are huge.I want to reduce memory footprint.Any suggestion for this.

So i have decided to fetch few rows at a time.How do i fetch rows using oledb command so that i can fetch for eg 1-20 and then 20-40 etc

Answer 1

Based on all the comments and HatSoft’s code here is what I think you are looking for. This is pseudo-code, whcih means it will not compile but should give you a good idea of where to go from here.

int NumberOfRecordsToRetrieve = 10000;
int StartRecordNumber = 1;
bool EndOfFile = false;

 string queryString = "SELECT OrderID, CustomerID FROM Orders WHERE RECNO() BETWEEN @StartRecordNumber AND @EndRecordNumber"; 

While (!EndOfFile)
{
     using (OleDbConnection connection = new OleDbConnection(connectionString)) 
     { 
         OleDbCommand command = new OleDbCommand(queryString, connection); 
         command.Parameters.Add(new OleDbParameter("@StartRecordNumber", StartRecordNumber)); 
         command.Parameters.Add(new OleDbParameter("@EndRecordNumber", StartRecordNumber + NumberOfRecordsToRetrieve)); 

         connection.Open(); 
         OleDbDataReader reader = command.ExecuteReader(); 

          EndOfFile = true;
          while (reader.Read()) 
          { 
               EndOfFile = false

               //Retrieve records here and do whatever process you wish to do
           } 
           reader.Close(); 

           StartRecordNumber += NumberOfRecordsToRetrieve;
     } 
}