mysqldumpslow -t 10 -s t -g “l(fā)eft join” slow.log

CREATE DATABASE test;           
use test;                       
drop table if exists t1;        

CREATE TABLE `t1` (            
 `id` int NOT NULL auto_increment,
  `a` int DEFAULT NULL,
  `b` int DEFAULT NULL,
  `create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '記錄創(chuàng)建時間',
  `update_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '記錄更新時間',
  PRIMARY KEY (`id`),
  KEY `idx_a` (`a`),
  KEY `idx_b` (`b`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;	

drop procedure if exists insert_t1; 
delimiter ;;
create procedure insert_t1()        
begin
  declare i int;                    
  set i=1;                          
  while(i<=1000)do                  
    insert into t1(a,b) values(i, i); 
    set i=i+1;                      
  end while;
end;;
delimiter ;                 
call insert_t1();           

drop table if exists t2;    
create table t2 like t1;    
insert into t2 select * from t1;  

select @@have_profiling;
select @@profiling;
set profiling=1;

select * from t1 where b=1000;
show profiles;
show profile for query 1;

set session optimizer_trace="enabled=on",end_markers_in_json=on;

select * from t1 where a >900 and b > 910 order  by a;

SELECT * FROM information_schema.OPTIMIZER_TRACE\G

*************************** 1. row ***************************
                            QUERY: select * from t1 where a >900 and b > 910 order  by a
                            TRACE: {
  "steps": [
    {
      "join_preparation": {
        "select#": 1,
        "steps": [
          {
            "expanded_query": "/* select#1 */ select `t1`.`id` AS `id`,`t1`.`a` AS `a`,`t1`.`b` AS `b`,`t1`.`create_time` AS `create_time`,`t1`.`update_time` AS `update_time` from `t1` where ((`t1`.`a` > 900) and (`t1`.`b` > 910)) order by `t1`.`a`"
          }
        ] /* steps */
      } /* join_preparation */
    },
    {
      "join_optimization": {
        "select#": 1,
        "steps": [
          {
            "condition_processing": {
              "condition": "WHERE",
              "original_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))",
              "steps": [
                {
                  "transformation": "equality_propagation",
                  "resulting_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))"
                },
                {
                  "transformation": "constant_propagation",
                  "resulting_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))"
                },
                {
                  "transformation": "trivial_condition_removal",
                  "resulting_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))"
                }
              ] /* steps */
            } /* condition_processing */
          },
          {
            "substitute_generated_columns": {
            } /* substitute_generated_columns */
          },
          {
            "table_dependencies": [
              {
                "table": "`t1`",
                "row_may_be_null": false,
                "map_bit": 0,
                "depends_on_map_bits": [
                ] /* depends_on_map_bits */
              }
            ] /* table_dependencies */
          },
          {
            "ref_optimizer_key_uses": [
            ] /* ref_optimizer_key_uses */
          },
          {
            "rows_estimation": [
              {
                "table": "`t1`",
                "range_analysis": {
                  "table_scan": {
                    "rows": 1000,
                    "cost": 103.35
                  } /* table_scan */,
                  "potential_range_indexes": [
                    {
                      "index": "PRIMARY",
                      "usable": false,
                      "cause": "not_applicable"
                    },
                    {
                      "index": "idx_a",
                      "usable": true,
                      "key_parts": [
                        "a",
                        "id"
                      ] /* key_parts */
                    },
                    {
                      "index": "idx_b",
                      "usable": true,
                      "key_parts": [
                        "b",
                        "id"
                      ] /* key_parts */
                    }
                  ] /* potential_range_indexes */,
                  "setup_range_conditions": [
                  ] /* setup_range_conditions */,
                  "group_index_range": {
                    "chosen": false,
                    "cause": "not_group_by_or_distinct"
                  } /* group_index_range */,
                  "skip_scan_range": {
                    "potential_skip_scan_indexes": [
                      {
                        "index": "idx_a",
                        "usable": false,
                        "cause": "query_references_nonkey_column"
                      },
                      {
                        "index": "idx_b",
                        "usable": false,
                        "cause": "query_references_nonkey_column"
                      }
                    ] /* potential_skip_scan_indexes */
                  } /* skip_scan_range */,
                  "analyzing_range_alternatives": {
                    "range_scan_alternatives": [
                      {
                        "index": "idx_a",
                        "ranges": [
                          "900 < a"
                        ] /* ranges */,
                        "index_dives_for_eq_ranges": true,
                        "rowid_ordered": false,
                        "using_mrr": false,
                        "index_only": false,
                        "in_memory": 1,
                        "rows": 100,
                        "cost": 35.26,
                        "chosen": true
                      },
                      {
                        "index": "idx_b",
                        "ranges": [
                          "910 < b"
                        ] /* ranges */,
                        "index_dives_for_eq_ranges": true,
                        "rowid_ordered": false,
                        "using_mrr": false,
                        "index_only": false,
                        "in_memory": 1,
                        "rows": 90,
                        "cost": 31.76,
                        "chosen": true
                      }
                    ] /* range_scan_alternatives */,
                    "analyzing_roworder_intersect": {
                      "usable": false,
                      "cause": "too_few_roworder_scans"
                    } /* analyzing_roworder_intersect */
                  } /* analyzing_range_alternatives */,
                  "chosen_range_access_summary": {
                    "range_access_plan": {
                      "type": "range_scan",
                      "index": "idx_b",
                      "rows": 90,
                      "ranges": [
                        "910 < b"
                      ] /* ranges */
                    } /* range_access_plan */,
                    "rows_for_plan": 90,
                    "cost_for_plan": 31.76,
                    "chosen": true
                  } /* chosen_range_access_summary */
                } /* range_analysis */
              }
            ] /* rows_estimation */
          },
          {
            "considered_execution_plans": [
              {
                "plan_prefix": [
                ] /* plan_prefix */,
                "table": "`t1`",
                "best_access_path": {
                  "considered_access_paths": [
                    {
                      "rows_to_scan": 90,
                      "access_type": "range",
                      "range_details": {
                        "used_index": "idx_b"
                      } /* range_details */,
                      "resulting_rows": 90,
                      "cost": 40.76,
                      "chosen": true,
                      "use_tmp_table": true
                    }
                  ] /* considered_access_paths */
                } /* best_access_path */,
                "condition_filtering_pct": 100,
                "rows_for_plan": 90,
                "cost_for_plan": 40.76,
                "sort_cost": 90,
                "new_cost_for_plan": 130.76,
                "chosen": true
              }
            ] /* considered_execution_plans */
          },
          {
            "attaching_conditions_to_tables": {
              "original_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))",
              "attached_conditions_computation": [
              ] /* attached_conditions_computation */,
              "attached_conditions_summary": [
                {
                  "table": "`t1`",
                  "attached": "((`t1`.`a` > 900) and (`t1`.`b` > 910))"
                }
              ] /* attached_conditions_summary */
            } /* attaching_conditions_to_tables */
          },
          {
            "optimizing_distinct_group_by_order_by": {
              "simplifying_order_by": {
                "original_clause": "`t1`.`a`",
                "items": [
                  {
                    "item": "`t1`.`a`"
                  }
                ] /* items */,
                "resulting_clause_is_simple": true,
                "resulting_clause": "`t1`.`a`"
              } /* simplifying_order_by */
            } /* optimizing_distinct_group_by_order_by */
          },
          {
            "reconsidering_access_paths_for_index_ordering": {
              "clause": "ORDER BY",
              "steps": [
              ] /* steps */,
              "index_order_summary": {
                "table": "`t1`",
                "index_provides_order": false,
                "order_direction": "undefined",
                "index": "idx_b",
                "plan_changed": false
              } /* index_order_summary */
            } /* reconsidering_access_paths_for_index_ordering */
          },
          {
            "finalizing_table_conditions": [
              {
                "table": "`t1`",
                "original_table_condition": "((`t1`.`a` > 900) and (`t1`.`b` > 910))",
                "final_table_condition   ": "((`t1`.`a` > 900) and (`t1`.`b` > 910))"
              }
            ] /* finalizing_table_conditions */
          },
          {
            "refine_plan": [
              {
                "table": "`t1`",
                "pushed_index_condition": "(`t1`.`b` > 910)",
                "table_condition_attached": "(`t1`.`a` > 900)"
              }
            ] /* refine_plan */
          },
          {
            "considering_tmp_tables": [
              {
                "adding_sort_to_table": "t1"
              } /* filesort */
            ] /* considering_tmp_tables */
          }
        ] /* steps */
      } /* join_optimization */
    },
    {
      "join_execution": {
        "select#": 1,
        "steps": [
          {
            "sorting_table": "t1",
            "filesort_information": [
              {
                "direction": "asc",
                "expression": "`t1`.`a`"
              }
            ] /* filesort_information */,
            "filesort_priority_queue_optimization": {
              "usable": false,
              "cause": "not applicable (no LIMIT)"
            } /* filesort_priority_queue_optimization */,
            "filesort_execution": [
            ] /* filesort_execution */,
            "filesort_summary": {
              "memory_available": 262144,
              "key_size": 9,
              "row_size": 32,
              "max_rows_per_buffer": 90,
              "num_rows_estimate": 90,
              "num_rows_found": 90,
              "num_initial_chunks_spilled_to_disk": 0,
              "peak_memory_used": 33792,
              "sort_algorithm": "std::sort",
              "unpacked_addon_fields": "skip_heuristic",
              "sort_mode": "<fixed_sort_key, additional_fields>"
            } /* filesort_summary */
          }
        ] /* steps */
      } /* join_execution */
    }
  ] /* steps */
}
MISSING_BYTES_BEYOND_MAX_MEM_SIZE: 0
          INSUFFICIENT_PRIVILEGES: 0

set session optimizer_trace="enabled=off";