find-item-duplicates.ps1

$sourceItems = Get-ChildItem -Recurse -Path "/sitecore/content/"
$query = "/sitecore/content//*[@@id!='{0}' and @OldUrl='{1}']"
$queryWithContains = "/sitecore/content//*[@@id!='{0}' and (@OldUrl='{1}' or contains(@OldUrl, '{2}'))]"

$foundDuplicatesCollection = New-Object System.Collections.ArrayList

Write-Host "SourceItemParentPath, SourceItemPath, SourceItemId, FoundDuplicateParentPath, FoundDuplicatePath, FoundDuplicateId, OriginalUrl, FoundDuplicateUrl"  -ForegroundColor Green

foreach ($sourceItem in $sourceItems) {
    $originalUrl = $sourceItem["OldUrl"]
    if ($originalUrl -eq "") {
        #Write-Host "Without original url - " $sourceItem.Paths.FullPath -ForegroundColor Magenta 
        continue
    }
    
    $builtQuery = ""
    
    # change this condition if you need a different or remove it completely
    # this condition checks links like old-domain.org?id=123456789
    if ($originalUrl -like '*?id=*') {
        $uri = New-Object -TypeName System.Uri -ArgumentList $originalUrl
        $id = [System.Web.HttpUtility]::ParseQueryString($uri.Query)["id"]
        $builtQuery = [string]::Format($queryWithContains, $sourceItem.ID, $originalUrl, "?id=" + $id)
    }
    else {
        $builtQuery = [string]::Format($query, $sourceItem.ID, $originalUrl)
    }
    
    #Write-Host $builtQuery
    $foundDuplicates = Get-Item -Path "master:" -Query $builtQuery
    
    foreach ($foundDuplicate in $foundDuplicates) {
        $reverseResults = $foundDuplicatesCollection | Where-Object { $_.SourceItemId -eq $foundDuplicate.ID -and $_.FoundDuplicateId -eq $sourceItem.ID }
        if ($reverseResults.Count -gt 0) {
            continue
        }
        
        $result = New-Object System.Object
        $result | Add-Member -MemberType NoteProperty -Name "SourceItemParentPath" -Value $sourceItem.Parent.Paths.FullPath
        $result | Add-Member -MemberType NoteProperty -Name "SourceItemPath" -Value $sourceItem.Paths.FullPath
        $result | Add-Member -MemberType NoteProperty -Name "SourceItemId" -Value $sourceItem.ID
        $result | Add-Member -MemberType NoteProperty -Name "FoundDuplicateParentPath" -Value $foundDuplicate.Parent.Paths.FullPath
        $result | Add-Member -MemberType NoteProperty -Name "FoundDuplicatePath" -Value $foundDuplicate.Paths.FullPath
        $result | Add-Member -MemberType NoteProperty -Name "FoundDuplicateId" -Value $foundDuplicate.ID
        $result | Add-Member -MemberType NoteProperty -Name "OriginalUrl" -Value $originalUrl
        $result | Add-Member -MemberType NoteProperty -Name "FoundDuplicateUrl" -Value $foundDuplicate["OldUrl"]
        $foundDuplicatesCollection.Add($result) | Out-Null
        
        Write-Host $result.SourceItemParentPath"," -ForegroundColor DarkYellow -NoNewline
        Write-Host $result.SourceItemPath"," -ForegroundColor DarkYellow -NoNewline
        Write-Host $result.SourceItemId"," -ForegroundColor DarkYellow -NoNewline
        Write-Host $result.FoundDuplicateParentPath"," -ForegroundColor Cyan -NoNewline
        Write-Host $result.FoundDuplicatePath"," -ForegroundColor Cyan -NoNewline
        Write-Host $result.FoundDuplicateId"," -ForegroundColor Cyan -NoNewline
        Write-Host $result.OriginalUrl"," -ForegroundColor DarkYellow -NoNewline
        Write-Host $result.FoundDuplicateUrl -ForegroundColor Cyan
    }
}