chunk_migrate.php

<?php

    public function migrate(Chunk $chunk, Shard $dstShard, array $schemas)
    {
        $shardId = $chunk->getShardId();
        if ($dstShard->id === $shardId) {
            throw new InvalidArgumentException("{$dstShard->id} == $shardId");
        }

        try {

            $created = $this->clone($chunk, $dstShard, $schemas);

            $missed = $this->verify($chunk, $dstShard, $schemas);

            $deleted = $this->remove($chunk, $schemas);

            return new MigrateResult(true, [
                'created' => $created,
                'missed'  => $missed,
                'deleted' => $deleted,
            ]);

        } catch (MigrateException $e) {

            $deleted = $this->removeFrom($chunk, $dstShard, $schemas);

            return new MigrateResult(false, [
                'deleted' => $deleted,
            ]);

        }
    }