你好，我在数据库中有一个表，它包含多个列，超过20个，它包含大约200万条记录
这个表有一个主键：col1，它也是我的表的索引，由于某些原因，该列的数据类型是varchar（200）。
我正在实现服务器端分页、排序和更高版本（过滤）
我在表演上遇到了一个问题，这是我的程序
DELIMITER $$
CREATE DEFINER=`master`@`%` PROCEDURE `spGetData`(
IN DisplayStart int ,
IN SortCol int ,
IN SortDir nvarchar(10),
IN Search nvarchar(255)
)
BEGIN
DECLARE FirstRec int;
DECLARE LastRec int;
SET FirstRec = DisplayStart;
select
col1,col2,col3,col4,col6,col7,col8,col9,col10,col11
col12,col13,col14,col15,col16,col17,col18,col19,col20
col21,
( select count(*) from myTable) as filtered
from myTable
order by
case When (@SortCol = 0 and @SortDir = 'asc') then col1 end asc ,
case When (@SortCol = 0 and @SortDir = 'desc') then col1 end desc ,
case When (@SortCol = 1 and @SortDir = 'asc') then col2 end asc ,
case When (@SortCol = 1 and @SortDir = 'desc') then col2 end desc ,
case When (@SortCol = 2 and @SortDir = 'asc') then col3 end asc ,
case When (@SortCol = 2 and @SortDir = 'desc') then col3 end desc ,
case When (@SortCol = 3 and @SortDir = 'asc') then col4 end asc ,
case When (@SortCol = 3 and @SortDir = 'desc') then col4 end desc ,
case When (@SortCol = 4 and @SortDir = 'asc') then col5 end asc ,
case When (@SortCol = 4 and @SortDir = 'desc') then col5 end desc ,
case When (@SortCol = 5 and @SortDir = 'asc') then col6 end asc ,
case When (@SortCol = 5 and @SortDir = 'desc') then col6 end desc ,
case When (@SortCol = 6 and @SortDir = 'asc') then col7 end asc ,
case When (@SortCol = 6 and @SortDir = 'desc') then col7 end desc ,
case When (@SortCol = 7 and @SortDir = 'asc') then col8 end asc ,
case When (@SortCol = 7 and @SortDir = 'desc') then col8 end desc ,
case When (@SortCol = 8 and @SortDir = 'asc') then col9 end asc ,
case When (@SortCol = 8 and @SortDir = 'desc') then col9 end desc ,
case When (@SortCol = 9 and @SortDir = 'asc') then col10 end asc ,
case When (@SortCol = 9 and @SortDir = 'desc') then col10 end desc ,
case When (@SortCol = 10 and @SortDir = 'asc') then col11 end asc ,
case When (@SortCol = 10 and @SortDir = 'desc') then col11 end desc ,
case When (@SortCol = 11 and @SortDir = 'asc') then col12 end asc ,
case When (@SortCol = 11 and @SortDir = 'desc') then col12 end desc ,
case When (@SortCol = 12 and @SortDir = 'asc') then col13 end asc ,
case When (@SortCol = 12 and @SortDir = 'desc') then col13 end desc ,
case When (@SortCol = 13 and @SortDir = 'asc') then col14 end asc ,
case When (@SortCol = 13 and @SortDir = 'desc') then col14 end desc ,
case When (@SortCol = 14 and @SortDir = 'asc') then col15 end asc ,
case When (@SortCol = 14 and @SortDir = 'desc') then col15 end desc ,
case When (@SortCol = 15 and @SortDir = 'asc') then col16 end asc ,
case When (@SortCol = 15 and @SortDir = 'desc') then col16 end desc ,
case When (@SortCol = 16 and @SortDir = 'asc') then col17 end asc ,
case When (@SortCol = 16 and @SortDir = 'desc') then col17 end desc ,
case When (@SortCol = 17 and @SortDir = 'asc') then col18 end asc ,
case When (@SortCol = 17 and @SortDir = 'desc') then col18 end desc ,
case When (@SortCol = 18 and @SortDir = 'asc') then col19 end asc ,
case When (@SortCol = 18 and @SortDir = 'desc') then col19 end desc ,
case When (@SortCol = 19 and @SortDir = 'asc') then col20 end asc ,
case When (@SortCol = 19 and @SortDir = 'desc') then col20 end desc ,
case When (@SortCol = 20 and @SortDir = 'asc') then col21 end asc ,
case When (@SortCol = 20 and @SortDir = 'desc') then col21 end desc ,
limit FirstRec,10;
END查询速度非常慢，并且会产生缓冲区大小问题。如果我删除ORDERBY子句，它会变得非常快。
所以我的问题是
1-如何增强此查询并快速对数百万行进行排序？
2-稍后我将使用where子句对多列应用筛选，如何避免任何性能问题？
1条答案
按热度按时间wwtsj6pe1#
这个
ORDER BY应该构造（concat、prepare、execute、deallocate）而不是拥有不能使用任何索引的庞大表达式。有可能，但不现实，添加
INDEX(col0), INDEX(col1), ...所以准备好的陈述在所有21个案例中都是快速的。选择重要的，不要把剩下的提供给最终用户。不要用偏移量分页；而是“记住你在哪里停下来了”。
过滤装置在哪里？这可能会干扰我已经给你的提示。
VARCHAR(200)通常是不明智的PRIMARY KEY.用户能否在两列上指定排序？筛选日期范围？其他事情(请提供真实的
SHOW CREATE TABLE如果你想了解更多细节。）你“规范化”过任何列吗？也就是说，将经常重复的大值移到其他表中。