Commandlet to split CSV file vertically in Powershell

Split-CSV.ps1

<#
    .SYNOPSIS

    Split CSV file vertically to have specified number of columns in each file

    .DESCRIPTION

    This is an example function how to split a wide file into multiple narrower files.
    Potential use cases could be importing data from a csv file into an SQL database,
    when number of columns in the CSV file is greater than the maximum table size.

    .PARAMETER Path

    Path to the input CSV file

    .PARAMETER Output

    Output file name with variable placeholder.

    .PARAMETER IdColumns

    List of columns to incude in every chunk. The list is assumed to be delimited with the same character as data

    .PARAMETER Delimiter

    What delimiter is used in the input file. The same will be used for the output.

    .PARAMETER ChunkSize

    How many columns (including ID columns) should be in each output. The last file may have less than that.

    .EXAMPLE

    PS> Split-CSV -Path "C:\Data\input_file.csv" -IdColumns "col1, col5" -Output "C:\Data\output_part{0}.csv"

    .EXAMPLE

    PS> Split-CSV -Path "~/data\input_file.csv" -IdColumns "proc_id;name" -Output "~/data\output_part{0}.csv" -Delimiter ";" -ChunkSize 1024
#>

function Split-CSV{
    param(
        $Path,
        $IdColumns,
        $Output,
        $Delimiter = ",",
        $ChunkSize = 10
    )

    $HeaderLine = (Get-Content $Path -Head 1).Split($Delimiter)

    if ($HeaderLine.length -le $ChunkSize) {
        Write-Host "Number of columns is already less than $ChunkSize."
        return
    }

    $IdIndices = $IdColumns.Split($Delimiter) | ForEach-Object {
        [array]::indexof($HeaderLine, $_.Trim())
    }

    $Headers = Split-Array $HeaderLine $IdIndices $ChunkSize $Delimiter

    $OutputFiles = 1..($Headers.length) | ForEach-Object {
        $file = $Output -f $_
        Remove-item -Path $file -Force -ErrorAction SilentlyContinue
        $file
    }

    Get-Content $Path | ForEach-Object {
        $row = Split-Array $_.Split($Delimiter) $IdIndices $ChunkSize $Delimiter
        for ($i=0; $i -lt $row.length; $i++) {
            Add-Content -Path $OutputFiles[$i] -Value $row[$i]
        }
    }
}

function Split-Array($Array, $Keep, $ChunkSize, $Delimiter) {

    $Size = $Array.length
    $l = 0
    $u = $l + $ChunkSize - 1
    $ret = @()
    While ($l -lt $Size) {
        $indices = $Keep + ($l..$u) | Sort-Object -Unique
        While ($indices.length -gt $ChunkSize) {
            $u = $u - 1
            $indices = $Keep + ($l..$u) | Sort-Object -Unique
        }
        $ret += ($Array[$indices] -join $Delimiter)
        $l = $u + 1
        $u = $l + $ChunkSize - 1
    }
    return $ret
}