WooCommerce bulk import and export with WP All Import, WP-CLI and EDD migration

// Skip rows whose unique key already exists and hasn't changed.
add_filter( 'wp_all_import_is_post_to_create', function ( $continue, $import_id, $data ) {
    $sku = $data['sku'] ?? '';
    if ( ! $sku ) {
        return false; // never import a row with no key
    }
    $existing = wc_get_product_id_by_sku( $sku );
    return $existing ? false : $continue; // let the Update pass handle it
}, 10, 3 );

// After save: keep the external ID for future delta syncs.
add_action( 'pmxi_saved_post', function ( $post_id, $xml_node, $is_update ) {
    if ( ! empty( $xml_node['external_id'] ) ) {
        update_post_meta( $post_id, '_external_id', sanitize_text_field( $xml_node['external_id'] ) );
    }
}, 10, 3 );

Rows with a missing key are rejected and existing SKUs go through the update pass, so re-running an import cannot create duplicates.

class My_Import_Command {
    public function __invoke( $args, $assoc_args ) {
        $batch   = (int) ( $assoc_args['batch'] ?? 500 );
        $dry_run = isset( $assoc_args['dry-run'] );
        $offset  = (int) get_option( 'my_import_offset', 0 );

        do {
            $rows = $this->fetch_rows( $offset, $batch );
            foreach ( $rows as $row ) {
                if ( $dry_run ) {
                    WP_CLI::log( "DRY: {$row['sku']}" );
                    continue;
                }
                try {
                    $this->upsert( $row );
                } catch ( Throwable $e ) {
                    WP_CLI::warning( "Row {$row['sku']}: " . $e->getMessage() );
                }
            }
            $offset += $batch;
            update_option( 'my_import_offset', $offset, false ); // checkpoint
            WP_CLI::log( "Imported up to offset {$offset}" );
        } while ( count( $rows ) === $batch );

        delete_option( 'my_import_offset' );
        WP_CLI::success( "Done at offset {$offset}" );
    }
}
WP_CLI::add_command( 'myplugin import', 'My_Import_Command' );

The checkpoint option makes a 250k-row import restartable after a timeout instead of a 6-hour restart.

// Copy the key AND its activations — otherwise live customers hit "limit reached".
$license = edd_software_licensing()->licenses_db->get_license( $old_license_id );

$new_key = $license->license_key; // keep the key stable for customers
update_post_meta( $new_order_id, '_edd_sl_license_key', $new_key );
update_post_meta( $new_order_id, '_edd_sl_expiration', $license->expiration );
update_post_meta( $new_order_id, '_edd_sl_activation_limit', $license->activation_limit );

$activations = edd_software_licensing()->get_license_activations( $old_license_id );
foreach ( $activations as $activation ) {
    // Re-register each site URL against the new licence record.
    my_migrate_activation( $new_key, $activation->site_name, $activation->site_url );
}

Most successful-looking migrations break here and the problem only shows up a week later in support.