MySql optimizer trace. No prepared statement.

trace-no-prepare.json

{
  "steps": [
    {
      "join_preparation": {
        "select#": 1,
        "steps": [
          {
            "expanded_query": "/* select#1 */ select `samples`.`id` AS `id`,`samples`.`organization_id` AS `organization_id`,`samples`.`device_id` AS `device_id`,`samples`.`percent_remaining` AS `percent_remaining`,`samples`.`percent_remaining_2` AS `percent_remaining_2`,`samples`.`created_at` AS `created_at`,`samples`.`updated_at` AS `updated_at`,`samples`.`raw_reading` AS `raw_reading`,`samples`.`filtered_reading` AS `filtered_reading`,`samples`.`raw_reading_2` AS `raw_reading_2`,`samples`.`signal_strength` AS `signal_strength`,`samples`.`battery_reading` AS `battery_reading`,`samples`.`basestation_id` AS `basestation_id` from `samples` where ((`samples`.`device_id` = 5852) and (`samples`.`device_id` is not null) and (`samples`.`id` <> 188315308)) order by `samples`.`created_at` desc limit 1"
          }
        ]
      }
    },
    {
      "join_optimization": {
        "select#": 1,
        "steps": [
          {
            "condition_processing": {
              "condition": "WHERE",
              "original_condition": "((`samples`.`device_id` = 5852) and (`samples`.`device_id` is not null) and (`samples`.`id` <> 188315308))",
              "steps": [
                {
                  "transformation": "equality_propagation",
                  "resulting_condition": "((5852 is not null) and (`samples`.`id` <> 188315308) and multiple equal(5852, `samples`.`device_id`))"
                },
                {
                  "transformation": "constant_propagation",
                  "resulting_condition": "((5852 is not null) and (`samples`.`id` <> 188315308) and multiple equal(5852, `samples`.`device_id`))"
                },
                {
                  "transformation": "trivial_condition_removal",
                  "resulting_condition": "((`samples`.`id` <> 188315308) and multiple equal(5852, `samples`.`device_id`))"
                }
              ]
            }
          },
          {
            "substitute_generated_columns": {
            }
          },
          {
            "table_dependencies": [
              {
                "table": "`samples`",
                "row_may_be_null": false,
                "map_bit": 0,
                "depends_on_map_bits": [
                ]
              }
            ]
          },
          {
            "ref_optimizer_key_uses": [
              {
                "table": "`samples`",
                "field": "device_id",
                "equals": "5852",
                "null_rejecting": true
              }
            ]
          },
          {
            "rows_estimation": [
              {
                "table": "`samples`",
                "range_analysis": {
                  "table_scan": {
                    "rows": 179018862,
                    "cost": 1.85e7
                  },
                  "potential_range_indexes": [
                    {
                      "index": "PRIMARY",
                      "usable": true,
                      "key_parts": [
                        "id"
                      ]
                    },
                    {
                      "index": "samples_organization_id_foreign",
                      "usable": false,
                      "cause": "not_applicable"
                    },
                    {
                      "index": "samples_basestation_id_created_at_index",
                      "usable": false,
                      "cause": "not_applicable"
                    },
                    {
                      "index": "samples_reverse_device_id_created_at_organization_id_index",
                      "usable": true,
                      "key_parts": [
                        "device_id",
                        "created_at",
                        "organization_id",
                        "id"
                      ]
                    }
                  ],
                  "setup_range_conditions": [
                  ],
                  "group_index_range": {
                    "chosen": false,
                    "cause": "not_group_by_or_distinct"
                  },
                  "skip_scan_range": {
                    "potential_skip_scan_indexes": [
                      {
                        "index": "PRIMARY",
                        "usable": false,
                        "cause": "query_references_nonkey_column"
                      },
                      {
                        "index": "samples_reverse_device_id_created_at_organization_id_index",
                        "usable": false,
                        "cause": "query_references_nonkey_column"
                      }
                    ]
                  },
                  "analyzing_range_alternatives": {
                    "range_scan_alternatives": [
                      {
                        "index": "PRIMARY",
                        "ranges": [
                          "id < 188315308",
                          "188315308 < id"
                        ],
                        "index_dives_for_eq_ranges": true,
                        "rowid_ordered": true,
                        "using_mrr": false,
                        "index_only": false,
                        "rows": 89509436,
                        "cost": 9.12e6,
                        "chosen": true
                      },
                      {
                        "index": "samples_reverse_device_id_created_at_organization_id_index",
                        "ranges": [
                          "5852 <= device_id <= 5852"
                        ],
                        "index_dives_for_eq_ranges": true,
                        "rowid_ordered": false,
                        "using_mrr": false,
                        "index_only": false,
                        "rows": 647136,
                        "cost": 550775,
                        "chosen": true
                      }
                    ],
                    "analyzing_roworder_intersect": {
                      "usable": false,
                      "cause": "too_few_roworder_scans"
                    }
                  },
                  "chosen_range_access_summary": {
                    "range_access_plan": {
                      "type": "range_scan",
                      "index": "samples_reverse_device_id_created_at_organization_id_index",
                      "rows": 647136,
                      "ranges": [
                        "5852 <= device_id <= 5852"
                      ]
                    },
                    "rows_for_plan": 647136,
                    "cost_for_plan": 550775,
                    "chosen": true
                  }
                }
              }
            ]
          },
          {
            "considered_execution_plans": [
              {
                "plan_prefix": [
                ],
                "table": "`samples`",
                "best_access_path": {
                  "considered_access_paths": [
                    {
                      "access_type": "ref",
                      "index": "samples_reverse_device_id_created_at_organization_id_index",
                      "rows": 647136,
                      "cost": 550774,
                      "chosen": true
                    },
                    {
                      "access_type": "range",
                      "range_details": {
                        "used_index": "samples_reverse_device_id_created_at_organization_id_index"
                      },
                      "chosen": false,
                      "cause": "heuristic_index_cheaper"
                    }
                  ]
                },
                "condition_filtering_pct": 50,
                "rows_for_plan": 323568,
                "cost_for_plan": 550774,
                "chosen": true
              }
            ]
          },
          {
            "attaching_conditions_to_tables": {
              "original_condition": "((`samples`.`device_id` = 5852) and (`samples`.`id` <> 188315308))",
              "attached_conditions_computation": [
              ],
              "attached_conditions_summary": [
                {
                  "table": "`samples`",
                  "attached": "((`samples`.`device_id` = 5852) and (`samples`.`id` <> 188315308))"
                }
              ]
            }
          },
          {
            "optimizing_distinct_group_by_order_by": {
              "simplifying_order_by": {
                "original_clause": "`samples`.`created_at` desc",
                "items": [
                  {
                    "item": "`samples`.`created_at`"
                  }
                ],
                "resulting_clause_is_simple": true,
                "resulting_clause": "`samples`.`created_at` desc"
              }
            }
          },
          {
            "reconsidering_access_paths_for_index_ordering": {
              "clause": "ORDER BY",
              "steps": [
              ],
              "index_order_summary": {
                "table": "`samples`",
                "index_provides_order": true,
                "order_direction": "asc",
                "index": "samples_reverse_device_id_created_at_organization_id_index",
                "plan_changed": false
              }
            }
          },
          {
            "finalizing_table_conditions": [
              {
                "table": "`samples`",
                "original_table_condition": "((`samples`.`device_id` = 5852) and (`samples`.`id` <> 188315308))",
                "final_table_condition   ": "(`samples`.`id` <> 188315308)"
              }
            ]
          },
          {
            "refine_plan": [
              {
                "table": "`samples`",
                "pushed_index_condition": "(`samples`.`id` <> 188315308)",
                "table_condition_attached": null
              }
            ]
          },
          {
            "considering_tmp_tables": [
            ]
          }
        ]
      }
    },
    {
      "join_execution": {
        "select#": 1,
        "steps": [
        ]
      }
    }
  ]
}