Improving DataReader Performance with Typed Accessors

[ Team LiB ]Recipe 9.6 Improving DataReader Performance with Typed Accessors Problem You need to improve performance when accessing data from a DataReader.. The sample code measures th

[ Team LiB ]

Recipe 9.6 Improving DataReader Performance with Typed Accessors

Problem

You need to improve performance when accessing data from a DataReader

Solution

Use DataReader typed accessors to improve performance by eliminating repeated boxing and unboxing of object data to and from NET Framework data types

The sample code measures the time to access data in a DataReader using three

techniques: typed accessor, column ordinal, and column name The user specifies the technique by selecting a radio button To ensure accuracy in each case, the routine reads all data from the DataReader 100 times and measures the total time in ticks, which are 100-nanosecond intervals

The C# code is shown in Example 9-10

Example 9-10 File: DataReaderPerformanceForm.cs

// Namespaces, variables, and constants

using System;

using System.Configuration;

using System.Windows.Forms;

using System.Data;

using System.Data.SqlClient;

//

Cursor.Current = Cursors.WaitCursor;

int orderId;

String customerId;

int employeeId;

DateTime orderDate;

DateTime requiredDate;

DateTime shippedDate;

int shipVia;

Decimal freight;

String shipName;

String shipAddress;

String shipCity;

String shipRegion;

String shipPostalCode;

String shipCountry;

String sqlText = "SELECT OrderID, CustomerID, EmployeeID, " +

"OrderDate, RequiredDate, ShippedDate, " +

"ShipVia, Freight, ShipName, ShipAddress, ShipCity, " +

"ShipRegion, ShipPostalCode, ShipCountry " +

"FROM Orders";

// Create the connection and the command

SqlConnection conn = new SqlConnection(

ConfigurationSettings.AppSettings["Sql_ConnectString"]);

SqlCommand cmd = new SqlCommand(sqlText, conn);

String accessMethod = typedAccessorRadioButton.Checked ? "Typed accessor": ordinalRadioButton.Checked ? "Ordinal":"Column name";

int startTick = 0;

int elapsedTick = 0;

conn.Open( );

for(int i = 1; i < 100; i++)

{

// Create the DataReader and retrieve all fields for each

// record in the DataReader according to user request

SqlDataReader dr = cmd.ExecuteReader( );

if (typedAccessorRadioButton.Checked)

{

startTick = Environment.TickCount;

while (dr.Read( ))

{

orderId = dr.GetInt32(0);

if(!dr.IsDBNull(1))

customerId = dr.GetString(1);

if(!dr.IsDBNull(2))

employeeId = dr.GetInt32(2);

if(!dr.IsDBNull(3))

orderDate = dr.GetDateTime(3);

if(!dr.IsDBNull(4))

requiredDate = dr.GetDateTime(4);

if(!dr.IsDBNull(5))

shippedDate = dr.GetDateTime(5);

if(!dr.IsDBNull(6))

shipVia = dr.GetInt32(6);

if(!dr.IsDBNull(7))

freight = dr.GetDecimal(7);

if(!dr.IsDBNull(8))

shipName = dr.GetString(8);

if(!dr.IsDBNull(9))

shipAddress = dr.GetString(9);

if(!dr.IsDBNull(10))

shipCity = dr.GetString(10);

if(!dr.IsDBNull(11))

shipRegion = dr.GetString(11);

if(!dr.IsDBNull(12))

shipPostalCode = dr.GetString(12);

if(!dr.IsDBNull(13))

shipCountry = dr.GetString(13);

}

elapsedTick += Environment.TickCount-startTick; }

if (ordinalRadioButton.Checked)

{

startTick = Environment.TickCount;

while (dr.Read( ))

{

if (!dr.IsDBNull(0))

orderId = Convert.ToInt32(dr[0]);

if (!dr.IsDBNull(1))

customerId = Convert.ToString(dr[1]);

if (!dr.IsDBNull(2))

employeeId = Convert.ToInt32(dr[2]);

if (!dr.IsDBNull(3))

orderDate = Convert.ToDateTime(dr[3]);

if (!dr.IsDBNull(4))

requiredDate = Convert.ToDateTime(dr[4]);

if (!dr.IsDBNull(5))

shippedDate = Convert.ToDateTime(dr[5]);

if (!dr.IsDBNull(6))

shipVia = Convert.ToInt32(dr[6]);

if (!dr.IsDBNull(7))

freight = Convert.ToDecimal(dr[7]);

if (!dr.IsDBNull(8))

shipName = Convert.ToString(dr[8]);

if (!dr.IsDBNull(9))

shipAddress = Convert.ToString(dr[9]);

if (!dr.IsDBNull(10))

shipCity = Convert.ToString(dr[10]);

if (!dr.IsDBNull(11))

shipRegion = Convert.ToString(dr[11]);

if (!dr.IsDBNull(12))

shipPostalCode = Convert.ToString(dr[12]);

if (!dr.IsDBNull(13))

shipCountry = Convert.ToString(dr[13]);

}

elapsedTick += Environment.TickCount-startTick;

}

if (columnNameRadioButton.Checked)

{

startTick = Environment.TickCount;

while (dr.Read( ))

{

if (dr["OrderID"] != DBNull.Value)

orderId = Convert.ToInt32(dr["OrderID"]);

if (dr["CustomerID"] != DBNull.Value)

customerId = Convert.ToString(dr["CustomerID"]);

if (dr["EmployeeID"] != DBNull.Value)

employeeId = Convert.ToInt32(dr["EmployeeID"]);

if (dr["OrderDate"] != DBNull.Value)

orderDate = Convert.ToDateTime(dr["OrderDate"]);

if (dr["RequiredDate"] != DBNull.Value)

requiredDate =

Convert.ToDateTime(dr["RequiredDate"]);

if (dr["ShippedDate"] != DBNull.Value)

shippedDate =

Convert.ToDateTime(dr["ShippedDate"]);

if (dr["ShipVia"] != DBNull.Value)

shipVia = Convert.ToInt32(dr["ShipVia"]);

if (dr["Freight"] != DBNull.Value)

freight = Convert.ToDecimal(dr["Freight"]);

if (dr["ShipName"] != DBNull.Value)

shipName = Convert.ToString(dr["ShipName"]);

if (dr["ShipAddress"] != DBNull.Value)

shipAddress = Convert.ToString(dr["ShipAddress"]);

if (dr["ShipCity"] != DBNull.Value)

shipCity = Convert.ToString(dr["ShipCity"]);

if (dr["ShipRegion"] != DBNull.Value)

shipRegion = Convert.ToString(dr["ShipRegion"]);

if (dr["ShipPostalCode"] != DBNull.Value)

shipPostalCode =

Convert.ToString(dr["ShipPostalCode"]);

if (dr["ShipCountry"] != DBNull.Value)

shipCountry = Convert.ToString(dr["ShipCountry"]);

}

elapsedTick += Environment.TickCount-startTick;

}

dr.Close( );

}

resultTextBox.Text += "Access method: " + accessMethod +

"; Elapsed time: " + elapsedTick + " ticks." + Environment.NewLine;

conn.Close( );

Cursor.Current = Cursors.Default;

Discussion

You can access the data in a DataReader row using a column name, a column ordinal, or

a typed accessor method such as GetInt32( ) and GetString( ) The typed accessor allows

a column value to be accessed in its native data type reducing the amount of type

conversion required when retrieving a column value When the underlying type is known, this reduces the type conversion effort required when retrieving the column value and thereby improves performance For a list of typed accessor methods for SQL Server and OLE DB data providers, see Recipe 2.8

Each typed accessor takes a single argument: the zero-based column ordinal of the

column for which to retrieve the value An IndexOutOfRangeException is raised if the ordinal value is not valid An InvalidCastException is raised if the accessor method

specifies an invalid cast If the column might contain a nonexistent or missing value, call the IsDBNull( ) method prior to calling the typed accessor method to avoid raising an exception in case the column value is equivalent to DBNull

Executing the solution shows the following relative performance when accessing

DataReader column values using the different methods:

• A column ordinal is about 30% faster than a column name

• A typed accessor method is about 15% faster than a column ordinal and 40%

faster than a column name

[ Team LiB ]