select * from information_schema.optimizer_trace limit 1;
QUERY	SELECT * FROM t2 WHERE id <= 3
TRACE	{
  "steps": [
    {
      "join_preparation": {
        "select_id": 1,
        "steps": [
          {
            "expanded_query": "select t2.`id` AS `id`,t2.msg AS msg from t2 where t2.`id` <= 3"
          }
        ]
      }
    },
    {
      "join_optimization": {
        "select_id": 1,
        "steps": [
          {
            "condition_processing": {
              "condition": "WHERE",
              "original_condition": "t2.`id` <= 3",
              "steps": [
                {
                  "transformation": "equality_propagation",
                  "resulting_condition": "t2.`id` <= 3"
                },
                {
                  "transformation": "constant_propagation",
                  "resulting_condition": "t2.`id` <= 3"
                },
                {
                  "transformation": "trivial_condition_removal",
                  "resulting_condition": "t2.`id` <= 3"
                }
              ]
            }
          },
          {
            "table_dependencies": [
              {
                "table": "t2",
                "row_may_be_null": false,
                "map_bit": 0,
                "depends_on_map_bits": []
              }
            ]
          },
          {
            "ref_optimizer_key_uses": []
          },
          {
            "rows_estimation": [
              {
                "table": "t2",
                "range_analysis": {
                  "table_scan": {
                    "rows": 7,
                    "cost": 0.113371474
                  },
                  "potential_range_indexes": [
                    {
                      "index": "PRIMARY",
                      "usable": true,
                      "key_parts": ["id"]
                    }
                  ],
                  "setup_range_conditions": [],
                  "analyzing_range_alternatives": {
                    "range_scan_alternatives": [
                      {
                        "index": "PRIMARY",
                        "ranges": ["(id) <= (3)"],
                        "rowid_ordered": false,
                        "using_mrr": false,
                        "index_only": false,
                        "rows": 2,
                        "cost": 0.004554858,
                        "chosen": false,
                        "cause": "cost"
                      }
                    ],
                    "analyzing_roworder_intersect": {
                      "cause": "too few roworder scans"
                    },
                    "analyzing_index_merge_union": []
                  },
                  "group_index_range": {
                    "chosen": false,
                    "cause": "no group by or distinct"
                  }
                }
              },
              {
                "selectivity_for_indexes": [
                  {
                    "index_name": "PRIMARY",
                    "selectivity_from_index": 0.285714286
                  }
                ],
                "selectivity_for_columns": [],
                "cond_selectivity": 0.285714286
              }
            ]
          },
          {
            "considered_execution_plans": [
              {
                "plan_prefix": "",
                "get_costs_for_tables": [
                  {
                    "best_access_path": {
                      "table": "t2",
                      "plan_details": {
                        "record_count": 1
                      },
                      "considered_access_paths": [
                        {
                          "access_type": "scan",
                          "rows": 7,
                          "rows_after_filter": 2,
                          "rows_out": 2,
                          "cost": 0.113371474,
                          "index_only": false,
                          "chosen": true
                        }
                      ],
                      "chosen_access_method": {
                        "type": "scan",
                        "rows_read": 2,
                        "rows_out": 2,
                        "cost": 0.113371474,
                        "uses_join_buffering": false
                      }
                    }
                  }
                ]
              },
              {
                "plan_prefix": "",
                "table": "t2",
                "rows_for_plan": 2,
                "cost_for_plan": 0.113371474
              }
            ]
          },
          {
            "best_join_order": ["t2"],
            "rows": 2,
            "cost": 0.113371474
          },
          {
            "substitute_best_equal": {
              "condition": "WHERE",
              "resulting_condition": "t2.`id` <= 3"
            }
          },
          {
            "attaching_conditions_to_tables": {
              "attached_conditions_computation": [
                {
                  "table_condition_pushdown": {
                    "table": "t2",
                    "push_cond": "t2.`id` <= 3"
                  }
                }
              ],
              "attached_conditions_summary": [
                {
                  "table": "t2",
                  "attached_condition": "t2.`id` <= 3"
                }
              ]
            }
          },
          {
            "make_join_readinfo": []
          }
        ]
      }
    }
  ]
}