PowerShellでCSVを取り込んでLeft Joinしたい

絶対昔書いてると思ったけど見つからなかった

Join-Table.ps1

function Join-Record {
    param($record1, $record2)
    $o = New-Object psobject

    $record1 | gm -MemberType NoteProperty | % {
        $name = $_.name
        $o | Add-Member NoteProperty -Name "$name" -Value $record1.$name
    }

    $record2 | gm -MemberType NoteProperty | % {
        $name = $_.name
        if ($o.psobject.properties.Name -contains $name) {
            $o | Add-Member NoteProperty -Name "Right.$name" -Value $record2.$name
        } else {
            $o | Add-Member NoteProperty -Name "$name" -Value $record2.$name
        }
    }
    return $o
}

function Join-Table {
    param(
        $From,
        $LeftJoin,
        $On,
        $Equal
    )

    $From | % {
        $FromRecord = $_
        $i = 0
        $LeftJoin | % {
            $LeftJoinRecord = $_
            if ($FromRecord.$On -eq $LeftJoinRecord.$Equal){
                Join-Record $FromRecord $LeftJoinRecord
                $i += 1
            }
        }
        if ($i -eq 0) {
            $PseudoLeftJoinRecord = New-Object psobject
            $LeftJoin | select-object -first 1 | % { $_.psobject.properties } | % {
                $PseudoLeftJoinRecord | Add-Member NoteProperty -Name $_.Name -Value ""
            }
            Join-Record $FromRecord $PseudoLeftJoinRecord
        }
    }
}

sample.ps1

. Join-Table.ps1

$a = 1..10 | % {
    [pscustomobject]@{
        Id = $_
        A = "A"
    }
}

$b = 1,2,3,4 | % {
    [pscustomobject]@{
        Id = $_
        B = "B"
    }
}

Join-Table -From $a -LeftJoin $b -On Id -Equal Id | ft -auto

A Id B Right.Id
- -- - --------
A  1 B        1
A  2 B        2
A  3 B        3
A  4 B        4
A  5           
A  6           
A  7           
A  8           
A  9           
A 10           

レコード数増えたら遅くなりそう。Excel に入れたい。