private function createVariant()
{
$table = $this->createTable('variant');
$table->addColumn('id', 'integer', ['autoincrement' => true]);
$table->addColumn('run_id', 'integer');
$table->addColumn('subject_id', 'integer');
$table->addColumn('sleep', 'integer', ['notnull' => false]);
$table->addColumn('output_time_unit', 'string', ['notnull' => false]);
$table->addColumn('output_time_precision', 'string', ['notnull' => false]);
$table->addColumn('output_mode', 'string', ['notnull' => false]);
$table->addColumn('revolutions', 'integer');
$table->addColumn('warmup', 'integer', ['notnull' => false]);
$table->addColumn('retry_threshold', 'float', ['notnull' => false]);
$table->setPrimaryKey(['id']);
$table->addForeignKeyConstraint($this->runTable, ['run_id'], ['id'], ['onDelete' => 'CASCADE']);
$table->addForeignKeyConstraint($this->subjectTable, ['subject_id'], ['id'], ['onDelete' => 'CASCADE']);
$this->variantTable = $table;
}