Most efficient way to delete row with VBA

Question

I currently have a macro that I use to delete a record if the ID doesn\'t exist in a list of ID\'s I created from an XML document. It does work like I want it to, however I

Answer 1

The short answer:

Use something like

ActiveSheet.Range(DelStr).Delete
' where DelStr = "15:15" if you want to delete row 15
'              = "15:15,20:20,32:32" if you want to delete rows 15,20 and 32

The long answer:

Important: If you have ~ 30 / 35 rows to delete, the following code works very efficiently. Beyond which it would throw up an error. For code to handle arbitrary number of rows efficiently see the very long answer below this.

If you have a function which lets you list out which rows you want to delete, try the code below. This is what I use to very efficiently delete multiple rows with minimum overhead. (the example assumes that you've obtained the rows you need to delete through some program, here I manually feed them in):

Sub DeleteRows()
    Dim DelRows() As Variant
    ReDim DelRows(1 To 3)

    DelRows(1) = 15
    DelRows(2) = 18
    DelRows(3) = 21

    '--- How to delete them all together?

    Dim i As Long
    For i = LBound(DelRows) To UBound(DelRows)
        DelRows(i) = DelRows(i) & ":" & DelRows(i)
    Next i

    Dim DelStr As String
    DelStr = Join(DelRows, ",")

    ' DelStr = "15:15,18:18,21:21"
    '           
    '    IMPORTANT: Range strings have a 255 character limit
    '    See the other code to handle very long strings

    ActiveSheet.Range(DelStr).Delete
End Sub

The (very long) efficient solution for arbitrary number of rows and benchmark results:

Here are the benchmark results obtained by deleting rows (Time in seconds vs. no. of rows).

The rows are on a clean sheet and contain a volatile formula in the D column from D1:D100000

i.e. for 100,000 rows, they have a formula =SIN(RAND())

The code is long and not too pretty, but it splits the DelStr into 250 character substrings and forms a range using these. Then the new DeleteRng range is deleted in a single operation.

The time to delete may depend on the contents of the cells. The testing/benchmarking, in congruence with a bit of intuition suggests the following results.

• Sparse rows/empty cells delete fastest
• Cells with values take somewhat longer
• Cells with formulas take even longer
• Cells which feed into formulas in other cells take longest as their deletion triggers the #Ref reference error.

Code:

Sub DeleteRows()

    ' Usual optimization
    ' Events not disabled as sometimes you'll need to interrupt
    ' You can optionally keep them disabled

    Application.Calculation = xlCalculationManual
    Application.ScreenUpdating = False

    ' Declarations...

    Dim DelRows() As Variant

    Dim DelStr As String, LenStr As Long
    Dim CutHere_Str As String
    Dim i As Long

    Dim MaxRowsTest As Long
    MaxRowsTest = 1000

    ' Here I'm taking all even rows from 1 to MaxRowsTest
    ' as rows to be deleted

    ReDim DelRows(1 To MaxRowsTest)

    For i = 1 To MaxRowsTest
        DelRows(i) = i * 2
    Next i

    '--- How to delete them all together?

    LenStr = 0
    DelStr = ""

    For i = LBound(DelRows) To UBound(DelRows)
        LenStr = LenStr + Len(DelRows(i)) * 2 + 2

        ' One for a comma, one for the colon and the rest for the row number
        ' The goal is to create a string like
        ' DelStr = "15:15,18:18,21:21"

        If LenStr > 200 Then
            LenStr = 0
            CutHere_Str = "!"       ' Demarcator for long strings
        Else
            CutHere_Str = ""
        End If

        DelRows(i) = DelRows(i) & ":" & DelRows(i) & CutHere_Str
    Next i

    DelStr = Join(DelRows, ",")

    Dim DelStr_Cut() As String
    DelStr_Cut = Split(DelStr, "!,")
    ' Each DelStr_Cut(#) string has a usable string

    Dim DeleteRng As Range
    Set DeleteRng = ActiveSheet.Range(DelStr_Cut(0))

    For i = LBound(DelStr_Cut) + 1 To UBound(DelStr_Cut)
        Set DeleteRng = Union(DeleteRng, ActiveSheet.Range(DelStr_Cut(i)))
    Next i

    DeleteRng.Delete

    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True

End Sub

The code to generate the formulas in a blank sheet is

Sub FillRandom()
    ActiveSheet.Range("D1").FormulaR1C1 = "=SIN(RAND())"
    Range("D1").AutoFill Destination:=Range("D1:D100000"), Type:=xlFillDefault
End Sub

And the code to generate the benchmark results above is

Sub TestTimeForDeletion()

        Call FillRandom

        Dim Time1 As Single, Time2 As Single
        Time1 = Timer

        Call DeleteRows

        Time2 = Timer
        MsgBox (Time2 - Time1)
End Sub

Note: Many thanks to brettdj for pointing out the error which gets thrown when the length of DelStr exceeding 255 characters. It seems to be a known problem and as I painfully found out, it still exists for Excel 2013.