SPAssignment and how to dispose correctly

Question

I have been doing a lot of scripting lately and came across memory considerations recently as we are in the phase of running scripts in production environments.

Basically what I do throughout my scripts is:

Start-SPAssignment -Global
Get-SPWebApplication $webApplicationUrl | Get-SPSite -Limit All | foreach {
    $_.AllWebs | foreach {
        $_.Lists | ? { $_.BaseType -eq "DocumentLibrary" } | foreach { 
            #Logic goes here like writing info about the list into CSV
        }
    }
}
Start-SPAssignment -Global

What we noticed after running above script in an environments with 3000+ site collections and 10000+ lists is that PowerShell process eats up to 1,5+ GB of memory, I guess I'm doing the disposal the wrong way! Or is that normal?

Should I try something like below instead?

Get-SPWebApplication $webApplicationUrl | Get-SPSite -Limit All | foreach {
    $siteAssignment = Start-SPAssignment
    $_.AllWebs | foreach {
        $webAssignment = Start-SPAssignment
        $_.Lists | ? { $_.BaseType -eq "DocumentLibrary" } | foreach {
            #Logic goes here like writing info about the list into CSV
        }
        Stop-SPAssignment $webAssignment
    }
    Stop-SPAssignment $siteAssignment
}

Or should I try a whole different approach? Thankful for you ideas over this case!

Answer 1

I would definitely dispose the SPSite and SPWeb you get from the Get-SPSite and $_.AllWebs at the end of each respective foreach loop.

Get-SPWebApplication $webApplicationUrl | Get-SPSite -Limit All | foreach {
    $siteAssignment = Start-SPAssignment
    $_.AllWebs | foreach {
        $webAssignment = Start-SPAssignment
        $_.Lists | ? { $_.BaseType -eq "DocumentLibrary" } | foreach {
            #Logic goes here like writing info about the list into CSV
        }        
        Stop-SPAssignment $webAssignment
        $_.Dispose() #<<<<<
    }    
    Stop-SPAssignment $siteAssignment
    $_.Dispose() #<<<<<
}

Answer 2

1,5+ GB with 3000+ site collections? That's nothing. While it's the best practice to dispose of SPWeb objects that you get from SPSite.AllWebs, it's only true when working with large amount of SPWebs, because when your SPSite is being disposed, all the child objects are disposed as well. And then again, when you close PowerShell, the memory is freed anyway. It's not like it's an IIS process which would free the leaked memory only when an iisreset is called. I would say you're safe with only SPSite.Dispose(), as the SPWeb.Dispose() will only introduce unnecessary overhead in your case.

Get-SPWebApplication $webApplicationUrl | Get-SPSite -Limit All | foreach {
    $siteAssignment = Start-SPAssignment
    $_.AllWebs | foreach {
        $_.Lists | ? { $_.BaseType -eq "DocumentLibrary" } | foreach { 
            #Logic goes here like writing info about the list into CSV
        }
    }
    Stop-SPAssignment $siteAssignment
    $_.Dispose()
}