{
  "steps": [
    {
      "join_optimization": {
        "select_id": 1,
        "steps": [
          {
            "rows_estimation": [
              {
                "table": "t1",
                "range_analysis": {
                  "table_scan": {
                    "rows": 1000,
                    "cost": 2e308
                  },
                  "potential_range_indexes": [
                    {
                      "index": "a_b",
                      "usable": true,
                      "key_parts": ["a", "b"]
                    }
                  ],
                  "best_covering_index_scan": {
                    "index": "a_b",
                    "cost": 52.195,
                    "chosen": true
                  },
                  "setup_range_conditions": [],
                  "group_index_range": {
                    "chosen": false,
                    "cause": "no group by or distinct"
                  },
                  "analyzing_range_alternatives": {
                    "range_scan_alternatives": [
                      {
                        "index": "a_b",
                        "ranges": ["2 <= a <= 2 AND 4 <= b <= 4"],
                        "rowid_ordered": true,
                        "using_mrr": false,
                        "index_only": true,
                        "rows": 1,
                        "cost": 1.1752,
                        "chosen": true
                      }
                    ],
                    "analyzing_roworder_intersect": {
                      "cause": "too few roworder scans"
                    },
                    "analyzing_index_merge_union": []
                  },
                  "chosen_range_access_summary": {
                    "range_access_plan": {
                      "type": "range_scan",
                      "index": "a_b",
                      "rows": 1,
                      "ranges": ["2 <= a <= 2 AND 4 <= b <= 4"]
                    },
                    "rows_for_plan": 1,
                    "cost_for_plan": 1.1752,
                    "chosen": true
                  }
                }
              },
              {
                "selectivity_for_indexes": [
                  {
                    "index_name": "a_b",
                    "selectivity_from_index": 0.001
                  }
                ],
                "selectivity_for_columns": [],
                "cond_selectivity": 0.001
              }
            ]
          }
        ]
      }
    },
    {
      "join_execution": {
        "select_id": 1,
        "steps": []
      }
    }
  ]
}