Die Order-Klausel in der Abfrage nimmt zu viel MySQL-Ladezeit in Anspruch

Question

Ich stecke in einer Situation fest, in der ich Millionen von Datensätzen habe und unterschiedliche Verbindungen für dieselben Datensätze benötige. Auch die Bestellbedingungen enthalten einige knifflige Teile. Wenn ich keine Sortierung anwende, liefert meine Abfrage schnelle Ergebnisse. Bei der Anwendung der Bestellklausel dauert es jedoch zu lange, bis das Ergebnis erzielt wird.

Ohne Order-Klausel ergibt das 5-6 Sekunden.

Bei Anwendung der Bestellbedingungen beträgt das Ergebnis 40-45 Sekunden

SELECT 
  forms_values.id,
  CASE
    WHEN forms_values.appointment_type = 2 
    AND user_patient_assinged_to_doctor.start_time IS NOT NULL 
    THEN 
    CASE
      WHEN patient_responded_tags_logs.tag_set_at IS NOT NULL 
      THEN 
      CASE
        WHEN UNIX_TIMESTAMP(
          CONVERT_TZ(
            patient_responded_tags_logs.tag_set_at,
            "+00:00",
            "-06:00"
          )
        ) > UNIX_TIMESTAMP(
          CONVERT_TZ(
            STR_TO_DATE(
              CONCAT(
                user_patient_assinged_to_doctor.date,
                " ",
                user_patient_assinged_to_doctor.start_time
              ),
              "%Y-%m-%d %h:%i %p"
            ),
            "+00:00",
            "-06:00"
          )
        ) 
        THEN UNIX_TIMESTAMP(
          CONVERT_TZ(
            patient_responded_tags_logs.tag_set_at,
            "+00:00",
            "-06:00"
          )
        ) 
        ELSE UNIX_TIMESTAMP(
          CONVERT_TZ(
            STR_TO_DATE(
              CONCAT(
                user_patient_assinged_to_doctor.date,
                " ",
                user_patient_assinged_to_doctor.start_time
              ),
              "%Y-%m-%d %h:%i %p"
            ),
            "+00:00",
            "-06:00"
          )
        ) 
      END 
      ELSE UNIX_TIMESTAMP(
        CONVERT_TZ(
          STR_TO_DATE(
            CONCAT(
              user_patient_assinged_to_doctor.date,
              " ",
              user_patient_assinged_to_doctor.start_time
            ),
            "%Y-%m-%d %h:%i %p"
          ),
          "+00:00",
          "-06:00"
        )
      ) 
    END 
    ELSE 
    CASE
      WHEN patient_responded_tags_logs.tag_set_at IS NOT NULL 
      THEN 
      CASE
        WHEN UNIX_TIMESTAMP(
          CONVERT_TZ(
            patient_responded_tags_logs.tag_set_at,
            "+00:00",
            "-06:00"
          )
        ) > UNIX_TIMESTAMP(forms_values.created_at) 
        THEN UNIX_TIMESTAMP(
          CONVERT_TZ(
            patient_responded_tags_logs.tag_set_at,
            "+00:00",
            "-06:00"
          )
        ) 
        ELSE UNIX_TIMESTAMP(forms_values.created_at) 
      END 
      ELSE UNIX_TIMESTAMP(forms_values.created_at) 
    END 
  END AS "consultation_date_time_ordering",
  CASE
    WHEN forms_values.appointment_type = 2 
    AND user_patient_assinged_to_doctor.start_time IS NOT NULL 
    THEN UNIX_TIMESTAMP(
      CONVERT_TZ(
        STR_TO_DATE(
          CONCAT(
            user_patient_assinged_to_doctor.date,
            " ",
            user_patient_assinged_to_doctor.start_time
          ),
          "%Y-%m-%d %h:%i %p"
        ),
        "+00:00",
        "-06:00"
      )
    ) 
    ELSE UNIX_TIMESTAMP(forms_values.created_at) 
  END AS "consultation_date_time" ,
  CASE
    WHEN forms_values.is_postpone = '1' 
    OR forms_values.is_completed = '8' 
    THEN 
    CASE
      WHEN UNIX_TIMESTAMP(
        CONVERT_TZ(
          STR_TO_DATE(
            CONCAT(UTC_DATE(), ' ', UTC_TIME()),
            '%Y-%m-%d %h:%i:%s'
          ),
          '+00:00',
          '-06:00'
        )
      ) < UNIX_TIMESTAMP(
        my_list_postpone.postponed_date
      ) 
      THEN 0 
      ELSE 1 
    END 
    ELSE 1 
  END AS "postponed_consultation_ordering"
FROM
  `forms_values` 
  LEFT JOIN `forms_values_completed_status_details` 
    ON `forms_values_completed_status_details`.`form_value_id` = `forms_values`.`id` 
  /*INNER JOIN `users` 
    ON `users`.`id` = `forms_values`.`patient_id` 
  LEFT JOIN `users` AS `doctors` 
    ON `doctors`.`id` = `forms_values`.`doctor_id`*/ 
  LEFT JOIN `user_patient_assinged_to_doctor` 
    ON `user_patient_assinged_to_doctor`.`form_value_id` = `forms_values`.`id` 
  INNER JOIN `states_countries` 
    ON `forms_values`.`state` = `states_countries`.`id` 
  LEFT JOIN `user_payment_history` 
    ON `user_payment_history`.`form_value_id` = `forms_values`.`id` 
  LEFT JOIN `emailed_tags_logs` 
    ON `emailed_tags_logs`.`form_value_id` = `forms_values`.`id` 
    AND `emailed_tags_logs`.`id` = 
    (SELECT 
      emailed_tags_logs.id 
    FROM
      emailed_tags_logs 
    WHERE emailed_tags_logs.form_value_id = forms_values.id 
      AND emailed_tags_logs.id = 
      (SELECT 
        emailed_tags_logs1.id AS emtid 
      FROM
        emailed_tags_logs AS emailed_tags_logs1 
      WHERE emailed_tags_logs1.form_value_id = forms_values.id 
      ORDER BY emailed_tags_logs1.created_at DESC 
      LIMIT 1) 
      AND emailed_tags_logs.status IN (1, 3) 
      AND emailed_tags_logs.is_pt_responded = "0" 
    ORDER BY emailed_tags_logs.created_at DESC 
    LIMIT 1) 
  LEFT JOIN `my_list_assign_doctor` 
    ON `my_list_assign_doctor`.`form_value_id` = `forms_values`.`id` 
    AND `my_list_assign_doctor`.`id` = 
    (SELECT 
      my_list_assign_doctor.id 
    FROM
      my_list_assign_doctor 
    WHERE my_list_assign_doctor.form_value_id = forms_values.id 
      AND my_list_assign_doctor.status IN (1, 2) 
      AND my_list_assign_doctor.prior_type = "others" 
    ORDER BY my_list_assign_doctor.created_at DESC 
    LIMIT 1) 
  LEFT JOIN `my_list_assign_doctor` AS `my_list_postpone` 
    ON `my_list_postpone`.`form_value_id` = `forms_values`.`id` 
    AND `forms_values`.`is_postpone` IN ('1', '2') 
    AND `my_list_postpone`.`id` = 
    (SELECT 
      my_list_assign_doctor.id 
    FROM
      my_list_assign_doctor 
    WHERE my_list_assign_doctor.form_value_id = forms_values.id 
      AND my_list_assign_doctor.prior_type = "postpone" 
    ORDER BY my_list_assign_doctor.created_at DESC 
    LIMIT 1) 
  LEFT JOIN `users` AS `partner` 
    ON `user_payment_history`.`std_partner_id` = `partner`.`id` 
  LEFT JOIN `patient_responded_tags_logs` 
    ON `patient_responded_tags_logs`.`form_value_id` = `forms_values`.`id` 
    AND `patient_responded_tags_logs`.`status` = '1' 
  LEFT JOIN `user_subscriptions` 
    ON `user_subscriptions`.`user_payment_history_id` = `user_payment_history`.`id` 
    AND `user_payment_history`.`form_value_id` = `forms_values`.`id` 
ORDER BY 
postponed_consultation_ordering DESC,
  `consultation_date_time` DESC 
LIMIT 10 OFFSET 0

Hinweis: Alle Verknüpfungen sind wichtig. Felder wurden aus bestimmten Gründen aus der Auswahlabfrage entfernt.

Erläuterungszusammenfassung

Answer 1

问题出在 LIMIT 和 ORDER BY 的组合上。

如果没有 ORDER BY，一旦选择了前十个随机行，查询就会停止。按照 order by 查询必须收集所有可能的行，然后按顺序对它们进行排序，然后仅返回前 10 行。

考虑到“postponed_consultation_datetime”是一个计算字段，确实没有办法让它更快。