SELECT 
  linked_promotion_id 
FROM 
  netting_product_bundles

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "netting_product_bundles",
          "access_type": "ALL",
          "rows": 3,
          "filtered": 100
        }
      }
    ]
  }
}