Powershell using Foreach-ObjectFast and Where-ObjectFast - windows

Question

I never really worked with Powershell, so I am quite stuck with this. My goal is to merge multiple CSV's into 1, more specifically 3 at the moment.
Using Import-Csv and Foreach-Object I managed to achieve this, however super-incredibly slow. I have discovered this article so I gave it a try. Incredible fast iteration.
Unfortunately I am too dumb with Powershell to understand why I cannot use Where-ObjectFast properly, it won't match anything.
My code example:
Measure-Command { $CSV1 = Import-CSV -Path .\CSV1.csv }
Measure-Command { $CSV2 = Import-CSV -Path .\CSV2.csv }
Measure-Command {
Import-Csv -Path .\CSV3.csv | Foreach-ObjectFast {
$row = $_;
$match = $CSV1 | Where-ObjectFast -FilterScript { $_.name -eq $row.'name' }
$dbg1 = 'Matched: {0}' -f $match; Write-Host $dbg1 -foreground Cyan;
# continued... } }
What I need to do basically is to match "name" from CVS3 with "name" from CSV1, and other fields as needed, then do the same for CSV2 and output to a final file.
It seems that when using Where-ObjectFast $_ is empty (?).
Please advise what I am doing wrong here, I would really appreciate it.

Answer 1

The problem you're having is not with the overhead from ForEach-Object binding and processing the input - so replacing ForEach-Object with ForEach-ObjectFast is not going to have a significant impact.
If you want to pivot on the name column (or any other column), build index tables with a hashtable/dictionary:
$CSV1 = #{}
Import-Csv -Path .\CSV1.csv |ForEach-Object { $CSV1[$_.name] = $_ }
$CSV2 = #{}
Import-Csv -Path .\CSV2.csv |ForEach-Object { $CSV2[$_.id] = $_ }
Now you don't need to wait for Where-Object to search through each collection:
Import-Csv -Path .\CSV3.csv |ForEach-Object {
$row = $_
# This is going to be MUCH faster than ... |Where-Object { ... }
$csv1match = $CSV1[$row.name]
$csv2match = $CSV1[$row.id]
# join $row,$csv1match,$csv2match here
}