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MySQL 5澳门新濠3559.7 跟踪优化器

时间:2019-11-09 19:29来源:数据库
Welcome to the MySQL monitor.  Commands end with ; or g. Your MySQL connection id is 5 Server version: 5.7.12 MySQL Community Server (GPL) Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rightsreserved. Oracle is a registered t

Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 5
Server version: 5.7.12 MySQL Community Server (GPL)

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> show variables like '%optimizer_trace%';
+------------------------------+----------------------------------------------------------------------------+
| Variable_name                | Value                                                                      |
+------------------------------+----------------------------------------------------------------------------+
| optimizer_trace              | enabled=off,one_line=off                                                   |
| optimizer_trace_features     | greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on |
| optimizer_trace_limit        | 1                                                                          |
| optimizer_trace_max_mem_size | 16384                                                                      |
| optimizer_trace_offset       | -1                                                                         |
+------------------------------+----------------------------------------------------------------------------+
5 rows in set (0.01 sec)

mysql> set optimizer_trace='enabled=on',end_markers_in_json=on;
Query OK, 0 rows affected (1.99 sec)

mysql> select * from fire.test;
+------+
| a    |
+------+
|   20 |
+------+
1 row in set (0.00 sec)

mysql> select * from information_schema.optimizer_traceG
*************************** 1. row ***************************
                            QUERY: select * from fire.test
                            TRACE: {
  "steps": [
    {
      "join_preparation": {
        "select#": 1,
        "steps": [
          {
            "expanded_query": "/* select#1 */ select `fire`.`test`.`a` AS `a` from `fire`.`test`"
          }
        ] /* steps */
      } /* join_preparation */
    },
    {
      "join_optimization": {
        "select#": 1,
        "steps": [
          {
            "table_dependencies": [
              {
                "table": "`fire`.`test`",
                "row_may_be_null": false,
                "map_bit": 0,
                "depends_on_map_bits": [
                ] /* depends_on_map_bits */
              }
            ] /* table_dependencies */
          },
          {
            "rows_estimation": [
              {
                "table": "`fire`.`test`",
                "table_scan": {
                  "rows": 1,
                  "cost": 1
                } /* table_scan */
              }
            ] /* rows_estimation */
          },
          {
            "considered_execution_plans": [
              {
                "plan_prefix": [
                ] /* plan_prefix */,
                "table": "`fire`.`test`",
                "best_access_path": {
                  "considered_access_paths": [
                    {
                      "rows_to_scan": 1,
                      "access_type": "scan",
                      "resulting_rows": 1,
                      "cost": 1.2,
                      "chosen": true
                    }
                  ] /* considered_access_paths */
                } /* best_access_path */,
                "condition_filtering_pct": 100,
                "rows_for_plan": 1,
                "cost_for_plan": 1.2,
                "chosen": true
              }
            ] /* considered_execution_plans */
          },
          {
            "attaching_conditions_to_tables": {
              "original_condition": null,
              "attached_conditions_computation": [
              ] /* attached_conditions_computation */,
              "attached_conditions_summary": [
                {
                  "table": "`fire`.`test`",
                  "attached": null
                }
              ] /* attached_conditions_summary */
            } /* attaching_conditions_to_tables */
          },
          {
            "refine_plan": [
              {
                "table": "`fire`.`test`"
              }
            ] /* refine_plan */
          }
        ] /* steps */
      } /* join_optimization */
    },
    {
      "join_execution": {
        "select#": 1,
        "steps": [
        ] /* steps */
      } /* join_execution */
    }
  ] /* steps */
}
MISSING_BYTES_BEYOND_MAX_MEM_SIZE: 0
          INSUFFICIENT_PRIVILEGES: 0
1 row in set (0.00 sec)

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