MariaDB [spider_2repmote_nodes]> explain FORMAT=JSON select count(1) from lots l inner join lot_extension le on l.lot_num = le.lot_num;
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| EXPLAIN                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
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| {
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "l",
      "access_type": "index",
      "possible_keys": ["lots_lot_num_IDX"],
      "key": "lots_lot_num_IDX",
      "key_length": "8",
      "used_key_parts": ["lot_num"],
      "rows": 35851118,
      "filtered": 100,
      "using_index": true
    },
    "table": {
      "table_name": "le",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "8",
      "used_key_parts": ["lot_num"],
      "ref": ["spider_2repmote_nodes.l.lot_num"],
      "rows": 1,
      "filtered": 100,
      "using_index": true
    }
  }
} |
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1 row in set (0.000 sec)

MariaDB [spider_2repmote_nodes]> exit