MySQL 存储过程优化

Question

我在 Mysql 中有以下存储过程。我的列必须是动态的，以便我将行转换为列。我有一个临时的 table 来存储我需要的数据，然后我将行连接成带有 if 语句的列，但我在 mysql 中遇到内存不足错误。有什么方法可以优化我的查询以在 mysql workbench（具有 4gb Ram 的 64 位操作系统）中高效工作？

 DELIMITER $$
 CREATE DEFINER=`root`@`localhost`
         PROCEDURE `myWordDistributionsQueryAll`(OUT myOutput text)
 BEGIN
  CREATE TEMPORARY TABLE IF NOT EXISTS tmpWeightTable
           (INDEX(word,topicName) ) ENGINE=MyISAM 
    AS  (

        SELECT wwt.topicName, t.topic_cnt as sumOfWordsInTopic,
               wwt.word, wwt.wordCount,
               (wwt.wordCount / t.topic_cnt) AS wordProbability
         FROM weightallofwordsintopic as wwt JOIN
             (SELECT topicName, sum(wordCount) AS topic_cnt
              FROM weightallofwordsintopic 
              GROUP BY topicName 
            ) t
         ON wwt.topicName = t.topicName
    );

    SET @sql = '';
    SELECT @sql := CONCAT(@sql,if(@sql='','',', '),temp.output)
    FROM
    (
        SELECT
          DISTINCT
            CONCAT(
             'SUM(IF(word = ''',
              word,
              ''', wordProbability, 0)) AS ',
              word
            ) as output
        FROM
            tmpWeightTable 
    ) as temp;


    SET @sql = CONCAT('SELECT topicName, ', @sql, ' FROM tmpWeightTable
          group by topicName order by topicName asc');
    SET myOutput=@sql;           
    END$$
    DELIMITER ;

Table:

CREATE TABLE weightallofwordsintopic (
    topicName varchar(200) DEFAULT NULL, 
    word varchar(100) DEFAULT NULL, 
    wordCount int(11) DEFAULT NULL, 
    KEY topicName_index (topicName), 
    KEY word_index (word)
) ENGINE=InnoDB DEFAULT CHARSET=latin5

Answer 1

SELECT @sql 里面的 'derived' table 不应该是

( SELECT CONCAT(
             SUM(...), ...
             word
         ) AS output
    FROM tmpWeightTable
    GROUP BY word )

这样就可以进行分组了，之前好像没有。

但可能还有另一个问题。那需要在里面

SELECT @list := GROUP_CONCAT(",", item)
    FROM ( SELECT 
                CONCAT("'", word,":", SUM(wordProbability), "'") AS item
            FROM tmpWeightTable
            GROUP BY word
          ) AS z;

然后把 sql 和

放在一起

SELECT @sql := CONCAT('SELECT topicName, ', @list, 
      ' FROM ??  group by topicName order by topicName asc');

我迷路了...请提供每个阶段的示例字符串。

MySQL 存储过程优化

MySQL Stored Procedure Optimization

mysql

stored-procedures

out-of-memory

query-optimization