Filter Relog counter files by SQL Server database names

filter-relog-counter-by-db.ps1

# extract counters first with relog.exe .\myfile.blg -q > counters.txt
$currentPath = $PSScriptRoot                                                                                                     # AzureDevOps, Powershell
if (!$currentPath) { $currentPath = Split-Path $pseditor.GetEditorContext().CurrentFile.Path -ErrorAction SilentlyContinue }     # VSCode
if (!$currentPath) { $currentPath = Split-Path $psISE.CurrentFile.FullPath -ErrorAction SilentlyContinue }                       # PsISE
if ($currentPath) { Set-Location $currentPath }

#$Databases = ("databasename");
$Databases = @(Get-Content (Join-Path $currentPath "databases.txt"));

$LinesRead = 0;
$CounterFileName = Join-Path $currentPath "counters.txt"
$FilteredFileName = $CounterFileName.Replace(".txt", "_filtered.txt");

try {
    $SourceFile = New-Object -TypeName System.IO.StreamReader -ArgumentList $CounterFileName;
    $FilteredFile = New-Object -TypeName System.IO.StreamWriter -ArgumentList $FilteredFileName;
    while (-not $SourceFile.EndOfStream) {
        $Line = $SourceFile.ReadLine().ToString();
        if ($Line -match "\\\\.*\\.*\\.*") {
            if ($Line -match "\\\\.*\\(?:SQLServer|MSSQL\$.*):Databases\((?<DatabaseName>.*)\)\\.*") {
                if ($matches["DatabaseName"] -in $Databases) {
                    $FilteredFile.WriteLine($Line)
                }
            }
            else {
                $FilteredFile.WriteLine($Line)
            }
        }
        $LinesRead++;
        if ($LinesRead % 5000 -eq 0) { Write-Host "Reading line $LinesRead"; };
    }
}
finally {
    $SourceFile.close()
    $FilteredFile.close()
}
# use the filtered counters file to filter the blg file e.g. relog .\MyFile.blg -cf .\counters_filtered.txt -o .\MyFile_filtered.blg