Compare Oracle Table with SQL Server Table and Update/Insert

Question

Below is the current code which is used to update/insert records from Oracle view to SQL Server table using Dapper. There is not a field to check last record updated date in the oracle view so I have added a method to get hashcode by using property values. Since Oracle table has more than 15k records and each record has more more than 60 columns, this approach take more than 5 minutes. Any ideas/suggestions to improve below code?

using System;
using System.Configuration;
using System.Data.OracleClient;
using System.Data.SqlClient;
using System.Linq;
using System.Reflection;
using Dapper;

namespace SyncSQLSvrWithHRDB
{
    internal class Program
    {
        public static PropertyInfo[] PropertyNames = typeof(Employee).GetProperties();

        private static void Main(string[] args)
        {
            var OracleConStr = ConfigurationManager.ConnectionStrings["OracleCon"].ConnectionString;
            var SqlSvrConStr = ConfigurationManager.ConnectionStrings["SqlSvrCon"].ConnectionString;
            using (OracleConnection OraCon = new OracleConnection(OracleConStr))
            {
                var res = OraCon.Query<Employee>(Constants.SelectSql).ToList();

                res = res.GroupBy(x => x.EmpNumber.ToUpper()).Select(x => x.LastOrDefault()).ToList();
                using (SqlConnection Sqlcon = new SqlConnection(SqlSvrConStr))
                {
                    Sqlcon.Open();
                    for (int i = 0; i < res.Count; i++)
                    {
                        var item = Sqlcon.Query<Employee>(Constants.SelectEmpSql, new { EmpNumber= res[i].EmpNumber}).FirstOrDefault();
                        if (item == null) // new record found
                        {
                            Sqlcon.Execute(Constants.InsertSql, res[i]);
                        }
                        else if (GetHashcode(res[i]) != GetHashcode(item)) // record updated
                        {
                            Sqlcon.Execute(Constants.UpdateSql, res[i]);
                        }
                    }
                }
            }
        }

        public static int GetHashcode(Employee o)
        {
            int ret = 0;
            foreach (var prop in PropertyNames)
            {
                object propValue = o.GetType().GetProperty(prop.Name).GetValue(o, null);

                if (propValue != null)
                {
                    ret += propValue.GetHashCode();
                }
            }

            return ret;
        }
    }

    public class Employee
    {
        public String EmpNumber{ get; set; }

        // ... other properties (70)
    }
}

Answer 1

One thing I would say is that you don't need to create those connection string variables, you are only using them once in this program and you have them nicely hidden where they should be, so you can just call them when you use them, which in this case is once.

so instead of this

var OracleConStr = ConfigurationManager.ConnectionStrings["OracleCon"].ConnectionString;
var SqlSvrConStr = ConfigurationManager.ConnectionStrings["SqlSvrCon"].ConnectionString;
using (OracleConnection OraCon = new OracleConnection(OracleConStr))
{
    var res = OraCon.Query<Employee>(Constants.SelectSql).ToList();

    res = res.GroupBy(x => x.EmpNumber.ToUpper()).Select(x => x.LastOrDefault()).ToList();
    using (SqlConnection Sqlcon = new SqlConnection(SqlSvrConStr))
    {

Do this instead

using (OracleConnection OraCon = new OracleConnection(ConfigurationManager.ConnectionStrings["OracleCon"].ConnectionString))
{
    var res = OraCon.Query<Employee>(Constants.SelectSql).ToList();

    res = res.GroupBy(x => x.EmpNumber.ToUpper()).Select(x => x.LastOrDefault()).ToList();
    using (SqlConnection Sqlcon = new SqlConnection(ConfigurationManager.ConnectionStrings["SqlSvrCon"].ConnectionString))
    {

You have already named them nicely so you know exactly what they are, meaning there is no reason to create variables for these, they are only used once.

---

and instead of a for loop here:

using (SqlConnection Sqlcon = new SqlConnection(SqlSvrConStr))
{
    Sqlcon.Open();
    for (int i = 0; i < res.Count; i++)
    {
        var item = Sqlcon.Query<Employee>(Constants.SelectEmpSql, new { EmpNumber= res[i].EmpNumber}).FirstOrDefault();
        if (item == null) // new record found
        {
            Sqlcon.Execute(Constants.InsertSql, res[i]);
        }
        else if (GetHashcode(res[i]) != GetHashcode(item)) // record updated
        {
            Sqlcon.Execute(Constants.UpdateSql, res[i]);
        }
    }
}

you could use a foreach loop

using (SqlConnection Sqlcon = new SqlConnection(SqlSvrConStr))
{
    Sqlcon.Open();

    foreach (var record in res)
    {
        var item = Sqlcon.Query<Employee>(Constants.SelectEmpSql, new { EmpNumber= record.EmpNumber}).FirstOrDefault();
        if (item == null) // new record found
        {
            Sqlcon.Execute(Constants.InsertSql, record);
        }
        else if (GetHashcode(record) != GetHashcode(item)) // record updated
        {
            Sqlcon.Execute(Constants.UpdateSql, record);
        }
    }
}

This is a little bit cleaner and is more straight to the point about what you are doing. I would probably change some variable names around, but I will let you have that fun.

Answer 2

This code queries the SQL server 15K times (for each and every employee in the Oracle view). Suggest generating the SQL query based on the Oracle view data set and retrieve the data from SQL in one go and then do the comparison in memory. You can generate the insert and update queries in the loop and execute them outside the loop as two batches if you have Dapper Plus ;)

Otherwise, you will have to instantiate a DataTable and populate it in the loop and use SQLBulkCopy for inserts.

Additionally, GetHashCode can be optimized as per below;

public static int GetHashcode(Employee o)
{
    int hashCode = 0;
    foreach (var property in PropertyNames)
    {
        object propValue = property.GetValue(o, null);
        if (propValue != null)
        {
            hashCode += propValue.GetHashCode();
        }
     }
    return hashCode;
}