Powershell script to get tag information from all Resource Groups

Question

I need to retrieve the "owner" tag that is associated to all Resource Groups for all Subscriptions in our tenant. I seem to be getting records that don't exist in the tenant. Maybe I'm going about this wrong but I thought I would iterate through all subscriptions and then iterate through all Resource groups and then go through the tag information. I get the same records for most of these resource groups. Can anyone spot the issue?

# Connect-AzAccount
$subs = Get-AzSubscription
$count = 1
foreach ($sub in $subs) {
    Set-AzContext -SubscriptionId $sub.SubscriptionId
    Write-Host $count. $sub.Name
    $count ++
    $resource_groups = Get-AzResourceGroup
    foreach ($rg in $resource_groups) {
        Write-Host '       ' $rg.ResourceGroupName
        $rgTags = Get-AzTag -Name 'owner'
        if ($rgTags -ne $null) {
            foreach ($tag in $rgTags.Values) {
                Write-Host '               '$tag.Name
            }
        }
    }
}

Answer 1

I would recommend using Search-AzGraph to query the Resource Manager API, it's much easier and faster with KQL than it will ever be with the individual cmdlets.

The query can be read as:

For each container in resourcecontainers where their type is microsoft.resources/subscriptions/resourcegroups and their owner Tag is not null or empty project the properties subscriptionId, resourceGroup, ownertag.

Search-AzGraph -Query @'
    resourcecontainers
    | where type =~ 'microsoft.resources/subscriptions/resourcegroups'
    | extend ownertag = tags.owner
    | where isnotempty(ownertag)
    | project subscriptionId, resourceGroup, ownertag
'@