Numbers are better than letters…

Back in a post from May (https://blogs.msdn.com/b/psssql/archive/2010/05/30/don-t-touch-that-schema.aspx), I reported that SSRS referenced fields by index instead of by name in code for performance benefits.  As a follow up to that, I decided to do some testing to demonstrate the performance benefit of this approach.  Here is the code I wrote for the testing  (note:  for simplicity’s sake, I am running this against a ReportServer catalog database):

 Imports System.Data.SqlClient
Imports System.Data

Module Module1

    Sub Main()

        Dim tsName As New DateTime
        Dim tsNum As New DateTime
        Dim teName As New DateTime
        Dim teNum As New DateTime

        Dim totalName As Long
        Dim totalNum As Long
        Dim iterations As Int16 = 10000
        Dim strCn As String = "Integrated Security=SSPI;Initial Catalog=ReportServer;Data Source=myserver”
        Dim cmdTxt As String = "select * from ExecutionLog2"

        For i As Int32 = 1 To iterations
            Dim cn As New SqlConnection(strCn)
            Dim cmd As New SqlCommand(cmdTxt, cn)
            cn.Open()
            Dim dr As SqlDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)

            'randomly pick a field number to reference
            Dim rand As New Random()
            Dim fieldnum As Int16 = rand.Next(0, dr.FieldCount - 1)

            'now, get it by index
            dr.Read()
            tsNum = DateTime.Now
            Dim val1 As Object = dr.Item(fieldnum)
            teNum = DateTime.Now
            totalNum += teNum.Subtract(tsNum).Ticks

            'close the connection
            cn.Close()

            If (i Mod 1000) = 0 Then Console.WriteLine(i)

        Next i
        Console.WriteLine("By index (ms): " + (totalNum / 10000).ToString)

        'Now repeat the process by name
        For i As Int32 = 1 To iterations
            Dim cn As New SqlConnection(strCn)
            Dim cmd As New SqlCommand(cmdTxt, cn)
            cn.Open()
            Dim dr As SqlDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)

            'randomly pick a field number to reference
            Dim rand As New Random()
            Dim fieldnum As Int16 = rand.Next(0, dr.FieldCount - 1)

            'now, get the field by name
            dr.Read()
            fieldnum = rand.Next(0, dr.FieldCount - 1)
            tsName = DateTime.Now
            Dim fieldname As String = KnownFieldName(fieldnum)
            Dim val2 As Object = dr.Item(fieldname)
            teName = DateTime.Now
            totalName += teName.Subtract(tsName).Ticks

            'close the connection
            cn.Close()

            If (i Mod 1000) = 0 Then Console.WriteLine(i)

        Next i
        Console.WriteLine("By name (ms): " + (totalName / 10000).ToString)

    End Sub

    Private Function KnownFieldName(ByVal num As Int16) As String
        Select Case num
            Case 0
                Return "InstanceName"
            Case 1
                Return "ReportPath"
            Case 2
                Return "UserName"
            Case 3
                Return "ExecutionId"
            Case 4
                Return "RequestType"
            Case 5
                Return "Format"
            Case 6
                Return "Parameters"
            Case 7
                Return "ReportAction"
            Case 8
                Return "TimeStart"
            Case 9
                Return "TimeEnd"
            Case 10
                Return "TimeDataRetrieval"
            Case 11
                Return "TimeProcessing"
            Case 12
                Return "TimeRendering"
            Case 13
                Return "Source"
            Case 14
                Return "Status"
            Case 15
                Return "ByteCount"
            Case 16
                Return "RowCount"
            Case 17
                Return "AdditionalInfo"
        End Select

        'if we don't hit a case statement, throw an exception
        Throw New System.NotSupportedException
    End Function



End Module

And, here’s the output:

 1000
2000
3000
By index (ms): 530053
1000
2000
3000
By name (ms): 1020102


1000
2000
3000
By index (ms): 580058
1000
2000
3000
By name (ms): 710071


1000
2000
3000
By index (ms): 510051
1000
2000
3000
By name (ms): 850085

As you can see, accessing the fields by index took an average of 540 seconds for 3000 iterations, or about 0.18 seconds per access.  Accessing them by name took 860 seconds for 3000 iterations, or about 0.29 seconds per access.  Personally, I’ll take 1/10th of a second of performance improvement when I am running a service that might serve thousands of simultaneous requests.

Evan Basalik | Senior Support Escalation Engineer | Microsoft SQL Server Escalation Services