Normalize WordPress Post Meta using PowerShell and CSV inputs

wp_normalize.ps1

# Import the CSV files
$posts_table = Import-Csv -Path "wp_posts.csv" | Group-Object -AsHashTable -Property 'ID'
$postmeta_table = Import-Csv -Path "wp_postmeta.csv" | Group-Object -Property 'post_id'
$relationships_table = Import-Csv -Path "wp_mb_relationships.csv" | Group-Object -Property 'from'

# remove subdirectory "Posts" if it exists
if (Test-Path ".\Posts") {
    Remove-Item -Path ".\Posts" -Recurse
}

# add subdirectory "Posts"
New-Item -ItemType Directory -Path ".\Posts"

# Use ConcurrentBag to store modified post objects
$postsWithMeta = New-Object System.Collections.Concurrent.ConcurrentBag[pscustomobject]

# Iterate over each metadata group
$posts_table.GetEnumerator() | ForEach-Object -Parallel {
    $post = $_
    $post_id = $_.Name

    # Add each meta key-value pair as a new property to the post object
    try {
        $postmeta_table = $using:postmeta_table
        $postmeta = $postmeta_table[$post_id]
        foreach ($meta in $postmeta) {
            $post = $post | Add-Member -MemberType NoteProperty -Name $meta.meta_key -Value $meta.meta_value -Force -PassThru
        }
    } catch {}

    # Add the modified post object to the ConcurrentBag
    $postsWithMeta = $Using:postsWithMeta
    $postsWithMeta.Add($post)
} -ThrottleLimit $env:NUMBER_OF_PROCESSORS

# Group the modified post objects by post_type
$posts_by_type = $postsWithMeta | Group-Object -Property post_type

# Export the posts of each type to their respective CSV files
foreach ($postType in $posts_by_type) {
    $posts_of_type = $postType.Group
    $posts_of_type | Export-Csv -Path ".\Posts\$($postType.Name).csv" -NoTypeInformation
}