How to sort a NotesDocumentCollection in Lotusscript

This Lotusscript function sorts a document collection on one or multiple fields.

I have previously used several other algorithms that use a view to sort the collection, these however have the drawback that they become very inefficient (i.e. slow) as the number of documents in the view used for sorting grows. The solution presented below does not have this problem.

It has been developed and tested in Lotus Notes 6.5.3 but should work in all ND6 (release 6) and possibly earlier Lotus Notes releases too (if you test this successfully or unsuccessfully write a comment to this post and everyone will know).

Example of use:

Dim fieldnames(0 To 2) As String
fieldnames(0) = "SKU"
fieldnames(1) = "OrderDate"
fieldnames(2) = "Client"
Set collection = SortCollection (collection, fieldnames)


Function to sort DocumentCollection:

Function SortCollection(coll As NotesDocumentCollection, fieldnames() As String) As NotesDocumentCollection

' ------------------------------------------------
' --- You may use and/or change this code freely
' --- provided you keep this message
' ---
' --- Description:
' --- Sorts and returns a NotesDocumentCollection
' --- Fieldnames parameter is an array of strings
' --- with the field names to be sorted on
' ---
' --- By Max Flodén 2005 - http://www.tjitjing.com
' ------------------------------------------------

Dim session As New NotesSession
Dim db As NotesDatabase
Dim collSorted As NotesDocumentCollection
Dim doc As NotesDocument
Dim i As Integer, n As Integer
Dim arrFieldValueLength() As Long
Dim arrSort, strSort As String
Dim viewname As String, fakesearchstring As String

viewname = "$All" 'This could be any existing view in database with first column sorted
fakesearchstring = "zzzzzzz" 'This search string must NOT match anything in view
Set db = session.CurrentDatabase

' ---
' --- 1) Build array to be sorted
' ---

'Fill array with fieldvalues and docid and get max field length
Redim arrSort(0 To coll.Count -1, 0 To Ubound(fieldnames) + 1)
Redim arrFieldValueLength(0 To Ubound(fieldnames) + 1)
For i = 0 To coll.Count - 1
Set doc = coll.GetNthDocument(i + 1)
For n = 0 To Ubound(fieldnames) + 1

If n = Ubound(fieldnames) + 1 Then
arrSort(i,n) = doc.UniversalID
arrFieldValueLength(n) = 32
Else
arrSort(i,n) = "" & doc.GetItemValue(fieldnames(n))(0)
' Check length of field value
If Len(arrSort(i,n)) > arrFieldValueLength(n) Then
arrFieldValueLength(n) = Len(arrSort(i,n))
End If
End If

Next n
Next i

'Merge fields into list that can be used for sorting using @Sort function
For i = 0 To coll.Count - 1
If Not strSort = "" Then strSort = strSort & ":"
strSort = strSort & """"
For n = Lbound(fieldnames) To Ubound(fieldnames) + 1
strSort = strSort & Left(arrSort(i,n) & Space(arrFieldValueLength(n)), arrFieldValueLength(n))
Next n
strSort = strSort & """"
Next i

' ---
' --- 2) Sort array
' ---
arrSort = Evaluate("@Sort(" & strSort & ")")

' ---
' --- 3) Use sorted array to sort collection
' ---
Set collSorted = coll.Parent.GetView(viewname).GetAllDocumentsByKey(fakesearchstring)

For i = 0 To Ubound(arrSort)
Set doc = db.GetDocumentByUNID(Right(arrSort(i), 32))
Call collSorted.AddDocument(doc)
Next i

' ---
' --- 4) Return collection
' ---
Set SortCollection = collSorted

End Function


(This article is previously published and has been moved to this blog)

[Update: Instead of using Evaluate and @Sort in section 2 in the code you can of course use any of your favourite sort routines. Or search the Net for one, there are many out there.]