mysql - 为什么这个简单的 MySQL 过程需要很长时间才能完成？

Question

这是一个非常简单的MySQL存储过程。游标“委托(delegate)”只有 3000 条记录，但程序调用需要 30 多秒才能运行。这是为什么？

DELIMITER //

DROP PROCEDURE IF EXISTS apply_credit//

CREATE PROCEDURE apply_credit()
BEGIN

  DECLARE done tinyint DEFAULT 0;
  DECLARE _pk_id INT;
  DECLARE _eid, _source VARCHAR(255);
  DECLARE _lh_revenue, _acc_revenue, _project_carrier_expense, _carrier_lh, _carrier_acc, _gross_margin, _fsc_revenue, _revenue, _load_count DECIMAL;

  DECLARE commission CURSOR FOR
    SELECT pk_id, eid, source, lh_revenue, acc_revenue, project_carrier_expense, carrier_lh, carrier_acc, gross_margin, fsc_revenue, revenue, load_count FROM ct_sales_commission;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

  DELETE FROM debug;

  OPEN commission;

  REPEAT
    FETCH commission INTO
      _pk_id, _eid, _source, _lh_revenue, _acc_revenue, _project_carrier_expense, _carrier_lh, _carrier_acc, _gross_margin, _fsc_revenue, _revenue, _load_count;
    INSERT INTO debug VALUES(concat('row ', _pk_id));

  UNTIL done = 1 END REPEAT;

  CLOSE commission;

END//

DELIMITER ;
CALL apply_credit();
SELECT * FROM debug;

Answer 1

如果你选择一些数据，插入到另一个表中，你可以这样做:

INSERT INTO debug 
SELECT concat('row ', _pk_id)
FROM ct_sales_commission;

它比使用游标更快。

---

一些小转弯:

• 删除表上的所有索引debug。

• 将 DELETE FROM 替换为 TRUNCATE TABLE。

• 在插入语句中添加DELAYED。

  INSERT DELAYED INTO ... VALUES(....)