ohmu/third/drupal/mustikas11/migrate_projekt_juurdepaas.php

<?php
use Drupal\Core\Database\Database;
use Drupal\node\Entity\Node;

$src = Database::getConnection('default', 'migrate');
$dst = Database::getConnection();

// Migreeri field_projekt_juurdepaas (projekt -> kasutajad).
// D7 tabel: field_data_field_projekt_juurdepaas (entity_id=projekt nid, target_id=user uid)
// D11 tabel: node__field_projekt_juurdepaas

$rows = $src->query(
  "SELECT entity_id, field_projekt_juurdepaas_target_id, delta
   FROM {field_data_field_projekt_juurdepaas}"
);

$count = 0;
$by_node = [];
foreach ($rows as $r) {
  $nid = (int) $r->entity_id;
  $uid = (int) $r->field_projekt_juurdepaas_target_id;

  // Kontrolli, et node ja kasutaja eksisteerivad D11-s.
  $node_exists = $dst->query('SELECT COUNT(*) FROM {node} WHERE nid = :nid', [':nid' => $nid])->fetchField();
  $user_exists = $dst->query('SELECT COUNT(*) FROM {users_field_data} WHERE uid = :uid', [':uid' => $uid])->fetchField();
  if (!$node_exists || !$user_exists) {
    echo "SKIP nid=$nid uid=$uid (puudub)\n";
    continue;
  }
  $by_node[$nid][] = $uid;
}

foreach ($by_node as $nid => $uids) {
  $node = Node::load($nid);
  if (!$node) {
    echo "SKIP NODE $nid\n";
    continue;
  }
  $node->set('field_projekt_juurdepaas', array_map(fn($u) => ['target_id' => $u], $uids));
  $node->save();
  $count++;
  echo "SET nid=$nid users=" . implode(',', $uids) . "\n";
}

echo "done, nodes updated: $count\n";