PowersShell: Quickly Split File with commas inside Quotes - performance

Question

I am dealing with the exact same question from here, but the answer in this post is actually worse than the originally posted problem. I have a csv file with 7 million records. I have run several tests of ways to read and write this file and once I introduce the regex split, the performance drops off significantly.
Below are some code examples (these have all the processing removed, and are just focusing on the reading, splitting and then writing back out as a .csv, in the real programs, there is processing of these fields, but that is the same regardless of the read and write method)
Does anyone have another suggestion to split a csv with commas in quotes efficiently?
Thank you.
When I use the standard split (which is fast, but creates issues because I have commas inside quoted fields) it runs fairly fast:
`
#CSV Split
$reader = [System.IO.File]::OpenText($path)
$writer = [System.IO.StreamWriter] $outputFileName1
measure-command {
while ($null -ne ($line = $reader.ReadLine())) {
$item = $line.Split(",")
$writer.WriteLine("{0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10},{11},{12},{13},{14},{15}"
, $item[0], $item[1], $item[2], $item[3], $item[4], $item[5], $item[6], $item[7], $item[8], $item[9]
, $item[10], $item[11], $item[12], $item[13], $item[14], $item[15])
}
}
$reader.Close()
$writer.Close()
`
TotalMinutes : 2.50485881
When I add Regex, it fixes the comma within quotes issue, but becomes VERY slow.
`
#regex Split
$RegexOptions = [System.Text.RegularExpressions.RegexOptions]
$csvSplit = '(,)(?=(?:[^"]|"[^"]*")*$)'
$reader = [System.IO.File]::OpenText($path)
$writer = [System.IO.StreamWriter] $outputFileName2
measure-command {
while ($null -ne ($line = $reader.ReadLine())) {
$item = [regex]::Split($Line, $csvSplit, $RegexOptions::ExplicitCapture)
$writer.WriteLine("{0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10},{11},{12},{13},{14},{15}"
, $item[0], $item[1], $item[2], $item[3], $item[4], $item[5], $item[6], $item[7], $item[8], $item[9]
, $item[10], $item[11], $item[12], $item[13], $item[14], $item[15])
}
}
$reader.Close()
$writer.Close()
`
TotalMinutes : 8.84508987333333
When I use the suggested answer from the link above, it becomes even slower.
`
`# With CSV
$writer = [System.IO.StreamWriter] $outputFileName3
measure-command {
Import-Csv $path | ForEach-Object {
$writer.WriteLine("{0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10},{11},{12},{13},{14},{15}"
, $_.BANK, $_.SOURCE, $_.ACCOUNT, $_.COSTCENTER, $_.TRANCD, $_.DOCNO, $_.TRACENO, $_.EFFDATE, $_.AMOUNT, $_.DESCRIP, $_.DESCRIP1, $_.DESCRIP3, $_.DESCRIP2, $_.DESCHYPH, $_.POSTDATE, $_.SJECHK)
}
}
$writer.Close()`
`
TotalMinutes : 18.0537001666667