{
  "steps": [
    {
      "join_preparation": {
        "select_id": 1,
        "steps": [
          {
            "join_preparation": {
              "select_id": 2,
              "steps": [
                {
                  "derived": {
                    "table": "dt",
                    "select_id": 3,
                    "algorithm": "materialized"
                  }
                },
                {
                  "join_preparation": {
                    "select_id": 3,
                    "steps": [
                      {
                        "expanded_query": "/* select#3 */ select t1.`id` AS `id`,avg(t1.a) AS `avg(a)`,t2.b AS b from (t1 join t2 on(t1.`id` = t2.id2))"
                      }
                    ]
                  }
                },
                {
                  "transformation": {
                    "select_id": 2,
                    "from": "IN (SELECT)",
                    "to": "semijoin",
                    "chosen": true
                  }
                },
                {
                  "expanded_query": "/* select#2 */ select dt.`id` from (/* select#3 */ select t1.`id` AS `id`,avg(t1.a) AS `avg(a)`,t2.b AS b from (t1 join t2 on(t1.`id` = t2.id2))) dt"
                }
              ]
            }
          },
          {
            "expanded_query": "/* select#1 */ select t1.`id` AS `id`,t1.a AS a from (t1 join t2 on(t1.`id` = t2.id2)) where t1.`id` in (/* select#2 */ select dt.`id` from (/* select#3 */ select t1.`id` AS `id`,avg(t1.a) AS `avg(a)`,t2.b AS b from (t1 join t2 on(t1.`id` = t2.id2))) dt)"
          }
        ]
      }
    },
    {
      "join_optimization": {
        "select_id": 1,
        "steps": [
          {
            "transformation": {
              "select_id": 2,
              "from": "IN (SELECT)",
              "to": "materialization",
              "sjm_scan_allowed": true,
              "possible": true
            }
          },
          {
            "transformation": {
              "select_id": 2,
              "from": "IN (SELECT)",
              "to": "semijoin",
              "converted_to_semi_join": true
            }
          },
          {
            "condition_processing": {
              "condition": "WHERE",
              "original_condition": "1 and t1.`id` = dt.`id` and t1.`id` = t2.id2",
              "steps": [
                {
                  "transformation": "equality_propagation",
                  "resulting_condition": "1 and multiple equal(t1.`id`, dt.`id`, t2.id2)"
                },
                {
                  "transformation": "constant_propagation",
                  "resulting_condition": "1 and multiple equal(t1.`id`, dt.`id`, t2.id2)"
                },
                {
                  "transformation": "trivial_condition_removal",
                  "resulting_condition": "multiple equal(t1.`id`, dt.`id`, t2.id2)"
                }
              ]
            }
          },
          {
            "join_optimization": {
              "select_id": 3,
              "steps": [
                {
                  "condition_processing": {
                    "condition": "WHERE",
                    "original_condition": "t1.`id` = t2.id2",
                    "steps": [
                      {
                        "transformation": "equality_propagation",
                        "resulting_condition": "multiple equal(t1.`id`, t2.id2)"
                      },
                      {
                        "transformation": "constant_propagation",
                        "resulting_condition": "multiple equal(t1.`id`, t2.id2)"
                      },
                      {
                        "transformation": "trivial_condition_removal",
                        "resulting_condition": "multiple equal(t1.`id`, t2.id2)"
                      }
                    ]
                  }
                },
                {
                  "table_dependencies": [
                    {
                      "table": "t1",
                      "row_may_be_null": false,
                      "map_bit": 0,
                      "depends_on_map_bits": []
                    },
                    {
                      "table": "t2",
                      "row_may_be_null": false,
                      "map_bit": 1,
                      "depends_on_map_bits": []
                    }
                  ]
                },
                {
                  "ref_optimizer_key_uses": [
                    {
                      "table": "t1",
                      "index": "id",
                      "field": "id",
                      "equals": "t2.id2",
                      "null_rejecting": true
                    }
                  ]
                },
                {
                  "rows_estimation": [
                    {
                      "table": "t1",
                      "table_scan": {
                        "rows": 8,
                        "read_cost": 0.0119028,
                        "read_and_compare_cost": 0.0121588
                      }
                    },
                    {
                      "table": "t2",
                      "table_scan": {
                        "rows": 4,
                        "read_cost": 0.0113788,
                        "read_and_compare_cost": 0.0115068
                      }
                    }
                  ]
                },
                {
                  "considered_execution_plans": [
                    {
                      "plan_prefix": "",
                      "get_costs_for_tables": [
                        {
                          "best_access_path": {
                            "table": "t2",
                            "plan_details": {
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                            },
                            "considered_access_paths": [
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                                "rows_out": 4,
                                "cost": 0.0115068,
                                "index_only": false,
                                "chosen": true
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                            ],
                            "chosen_access_method": {
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                              "rows_out": 4,
                              "cost": 0.0115068,
                              "uses_join_buffering": false
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                          }
                        },
                        {
                          "best_access_path": {
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                                "chosen": true
                              }
                            ],
                            "chosen_access_method": {
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                          }
                        }
                      ]
                    },
                    {
                      "plan_prefix": "",
                      "table": "t2",
                      "rows_for_plan": 4,
                      "cost_for_plan": 0.0115068,
                      "rest_of_plan": [
                        {
                          "plan_prefix": "t2",
                          "get_costs_for_tables": [
                            {
                              "best_access_path": {
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                                },
                                "considered_access_paths": [
                                  {
                                    "access_type": "ref",
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                                    "reason": "not available",
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                                    "cost": 0.02084032,
                                    "chosen": true
                                  },
                                  {
                                    "access_type": "scan_with_join_cache",
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                                ],
                                "chosen_access_method": {
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                          ]
                        },
                        {
                          "plan_prefix": "t2",
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                          "cost_for_plan": 0.026880776,
                          "pushdown_cond_selectivity": 0.5,
                          "filtered": 50,
                          "rows_out": 4
                        }
                      ]
                    },
                    {
                      "plan_prefix": "",
                      "table": "t1",
                      "rows_for_plan": 8,
                      "cost_for_plan": 0.0121588,
                      "pruned_by_heuristic": true
                    }
                  ]
                },
                {
                  "best_join_order": ["t2", "t1"],
                  "rows": 16,
                  "cost": 0.026880776
                },
                {
                  "substitute_best_equal": {
                    "condition": "WHERE",
                    "resulting_condition": "t1.`id` = t2.id2"
                  }
                },
                {
                  "attaching_conditions_to_tables": {
                    "attached_conditions_computation": [
                      {
                        "table": "t1",
                        "range_analysis": {
                          "table_scan": {
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                            "cost": 0.0121588
                          },
                          "potential_range_indexes": [
                            {
                              "index": "a",
                              "usable": false,
                              "cause": "not applicable"
                            },
                            {
                              "index": "id",
                              "usable": true,
                              "key_parts": ["id"]
                            }
                          ],
                          "setup_range_conditions": [],
                          "analyzing_range_alternatives": {
                            "range_scan_alternatives": [
                              {
                                "index": "id"
                              }
                            ],
                            "analyzing_roworder_intersect": {
                              "cause": "too few roworder scans"
                            },
                            "analyzing_index_merge_union": []
                          },
                          "group_index_range": {
                            "chosen": false,
                            "cause": "not single_table"
                          }
                        }
                      }
                    ],
                    "attached_conditions_summary": [
                      {
                        "table": "t2",
                        "attached_condition": null
                      },
                      {
                        "table": "t1",
                        "attached_condition": "t1.`id` = t2.id2"
                      }
                    ]
                  }
                },
                {
                  "make_join_readinfo": []
                }
              ]
            }
          },
          {
            "table_dependencies": [
              {
                "table": "t1",
                "row_may_be_null": false,
                "map_bit": 0,
                "depends_on_map_bits": []
              },
              {
                "table": "t2",
                "row_may_be_null": false,
                "map_bit": 1,
                "depends_on_map_bits": []
              },
              {
                "table": "<derived3>",
                "row_may_be_null": false,
                "map_bit": 2,
                "depends_on_map_bits": []
              }
            ]
          },
          {
            "ref_optimizer_key_uses": [
              {
                "table": "t1",
                "index": "id",
                "field": "id",
                "equals": "dt.`id`",
                "null_rejecting": true
              },
              {
                "table": "t1",
                "index": "id",
                "field": "id",
                "equals": "t2.id2",
                "null_rejecting": true
              },
              {
                "table": "<derived3>",
                "index": "key1",
                "field": "id",
                "equals": "t1.`id`",
                "null_rejecting": true
              },
              {
                "table": "<derived3>",
                "index": "key2",
                "field": "id",
                "equals": "t2.id2",
                "null_rejecting": true
              }
            ]
          },
          {
            "rows_estimation": [
              {
                "table": "t1",
                "table_scan": {
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                  "read_cost": 0.0119028,
                  "read_and_compare_cost": 0.0121588
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              },
              {
                "table": "t2",
                "table_scan": {
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                  "read_cost": 0.0113788,
                  "read_and_compare_cost": 0.0115068
                }
              },
              {
                "table": "<derived3>",
                "table_scan": {
                  "rows": 32,
                  "read_cost": 0.116782,
                  "read_and_compare_cost": 0.119753712
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              }
            ]
          },
          {
            "semijoin_table_pullout": {
              "pulled_out_tables": []
            }
          },
          {
            "execution_plan_for_potential_materialization": {
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                {
                  "considered_execution_plans": [
                    {
                      "plan_prefix": "",
                      "get_costs_for_tables": [
                        {
                          "best_access_path": {
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                                "rows_after_filter": 32,
                                "rows_out": 32,
                                "cost": 0.119753712,
                                "index_only": false,
                                "chosen": true
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                            ],
                            "chosen_access_method": {
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                              "rows_out": 32,
                              "cost": 0.119753712,
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                          }
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                      ]
                    },
                    {
                      "plan_prefix": "",
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              ]
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          },
          {
            "considered_execution_plans": [
              {
                "plan_prefix": "",
                "get_costs_for_tables": [
                  {
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                          "chosen": true
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                      ],
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                  },
                  {
                    "best_access_path": {
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                      "considered_access_paths": [
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                          "cause": "no predicate for first keypart"
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                          "cause": "no predicate for first keypart"
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                            {
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                      },
                      {
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                              "cause": "no predicate for first keypart"
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                            {
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                    ]
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                                  "cause": "cost"
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                                {
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                      },
                      {
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                          {
                            "strategy": "SJ-Materialization",
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                          {
                            "strategy": "DuplicateWeedout",
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                  },
                  {
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                          {
                            "strategy": "SJ-Materialization-Scan",
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                          {
                            "chosen_strategy": "LooseScan"
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                        ],
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              {
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                "cost_for_plan": 0.119753712,
                "semijoin_strategy_choice": [],
                "pruned_by_cost": true,
                "current_cost": 0.119753712,
                "best_cost": 0.051334104
              }
            ]
          },
          {
            "fix_semijoin_strategies_for_picked_join_order": [
              {
                "semi_join_strategy": "FirstMatch",
                "join_order": [
                  {
                    "table": "<derived3>"
                  }
                ]
              }
            ]
          }