SqlLabDataGenerator

2.0.0

internal/functions/generation/Group-SldgTablesByLevel.ps1

function Group-SldgTablesByLevel {
    <#
    .SYNOPSIS
        Groups topologically-ordered tables into dependency levels for parallel processing.
    .DESCRIPTION
        Assigns each table a dependency level: level 0 has no FK dependencies, level 1
        depends only on level 0 tables, etc. Tables at the same level are independent
        and can be generated in parallel.
    #>
    [CmdletBinding()]
    param (
        [Parameter(Mandatory)]
        [object[]]$Tables
    )

    $levelMap = @{}
    foreach ($table in $Tables) {
        $levelMap[$table.FullName] = 0
    }

    # Iteratively compute levels based on FK dependencies
    # Safety limit prevents infinite loop with circular FK dependencies (A→B→A)
    $maxIterations = $Tables.Count
    $iteration = 0
    $changed = $true
    $lastLevelSum = -1
    while ($changed) {
        if ($iteration++ -ge $maxIterations) {
            Write-PSFMessage -Level Warning -Message ($script:strings.'Generation.LevelComputationStopped' -f $maxIterations)
            break
        }
        $changed = $false
        foreach ($table in $Tables) {
            if (-not $table.ForeignKeys) { continue }

            $deps = $table.ForeignKeys |
                Where-Object { "$($_.ReferencedSchema).$($_.ReferencedTable)" -ne $table.FullName } |
                ForEach-Object { "$($_.ReferencedSchema).$($_.ReferencedTable)" } |
                Select-Object -Unique

            foreach ($dep in $deps) {
                if ($levelMap.ContainsKey($dep)) {
                    $requiredLevel = $levelMap[$dep] + 1
                    if ($requiredLevel -gt $levelMap[$table.FullName]) {
                        $levelMap[$table.FullName] = $requiredLevel
                        $changed = $true
                    }
                }
            }
        }

        # Convergence early exit: if level sums haven't changed, no further progress is possible
        $currentLevelSum = 0
        foreach ($v in $levelMap.Values) { $currentLevelSum += $v }
        if ($currentLevelSum -eq $lastLevelSum) { break }
        $lastLevelSum = $currentLevelSum
    }

    # Group by level, preserving original order within each level
    $maxLevel = 0
    foreach ($v in $levelMap.Values) { if ($v -gt $maxLevel) { $maxLevel = $v } }

    $groups = [System.Collections.Generic.List[object]]::new()
    for ($level = 0; $level -le $maxLevel; $level++) {
        $levelTables = @($Tables | Where-Object { $levelMap[$_.FullName] -eq $level })
        if ($levelTables.Count -gt 0) {
            $groups.Add([PSCustomObject]@{
                Level  = $level
                Tables = $levelTables
            })
        }
    }

    $firstGroupCount = if ($groups.Count -gt 0) { $groups[0].Tables.Count } else { 0 }
    Write-PSFMessage -Level Verbose -Message ($script:strings.'Generation.DependencyLevels' -f $groups.Count, $firstGroupCount)
    $groups.ToArray()
}