dbatools: Command for GitHub Copilot

Pipeline Output Patterns

CRITICAL RULE: NEVER collect objects in an ArrayList or array and output them at the end. Output objects to the pipeline immediately as they are created.

Why Immediate Output

• Memory Efficiency: Objects are released to the pipeline immediately, not held in memory
• User Experience: Users see results streaming in real-time, not waiting until the end
• Pipeline Compatibility: Enables proper pipeline chaining and early termination (Ctrl+C)
• Error Resilience: Partial results are available even if the command fails partway through

Correct Pattern - Output Immediately

foreach ($instance in $SqlInstance) {
    $server = Connect-DbaInstance -SqlInstance $instance -SqlCredential $SqlCredential

    foreach ($db in $server.Databases) {
        # Output each object immediately to the pipeline
        [PSCustomObject]@{
            ComputerName = $server.ComputerName
            InstanceName = $server.ServiceName
            SqlInstance  = $server.DomainInstanceName
            Database     = $db.Name
            Size         = $db.Size
        }
    }
}

Wrong Patterns - DO NOT USE

ArrayList Collection (OLD PATTERN)

# WRONG - This is an outdated anti-pattern
$results = New-Object System.Collections.ArrayList

foreach ($instance in $SqlInstance) {
    $server = Connect-DbaInstance -SqlInstance $instance -SqlCredential $SqlCredential

    foreach ($db in $server.Databases) {
        $null = $results.Add([PSCustomObject]@{
            ComputerName = $server.ComputerName
            Database     = $db.Name
        })
    }
}

# WRONG - Holding everything until the end
$results

Array Concatenation (Worst Performance)

# WRONG - Array concatenation is extremely slow
$results = @()

foreach ($db in $databases) {
    $results += [PSCustomObject]@{
        Name = $db.Name
    }
}

$results

No -Detailed or -Simple Parameters

Do NOT create -Detailed or -Simple switch parameters that change the output object structure. This is an outdated pattern that creates confusion and breaks pipeline expectations.