视图上奇怪的Mysql查询性能

Question

我有一个观点：vcompanyendofday

以下查询仅需0.7秒即可执行

Select * from vcompanyendofday

但是此查询的条件很简单，大约需要200.0秒

select * from vcompanyendofday where companyid <= 51;

这是视图定义：

 CREATE VIEW `vcompanyendofday` AS 
  select  `c`.`companyid` AS `companyid`,
          `c`.`scripcode` AS `scripcode`,
          `e`.`eoddate` AS `eoddate`,
          `e`.`prevclose` AS `prevclose`,
          `e`.`delqty` AS `delqty` 
  from    (
          `company` `c`
  left join
          `endofday` `e`
  on      ((`c`.`companyid` = `e`.`companyid`)))
  where   (`e`.`eoddate` =
          (
          select  max(`e2`.`eoddate`) AS `max(eoddate)`
          from    `endofday` `e2` 
          where (`e2`.`companyid` = `c`.`companyid`)
          )
  );

Answer 1

似乎您在endofday.companyid上没有索引

添加条件后， company将成为连接的领导者，并扼杀所有性能。

在endofday.companyid上创建索引：

CREATE INDEX ix_endofday_companyid ON endofday(companyid)

顺便说一句，如果您想退回所有公司，则需要将子查询放入OUTER JOIN的ON子句中，否则您丢失的endofday将会被过滤掉：

CREATE VIEW `vcompanyendofday` AS 
select  `c`.`companyid` AS `companyid`,
        `c`.`scripcode` AS `scripcode`,
        `e`.`eoddate` AS `eoddate`,
        `e`.`prevclose` AS `prevclose`,
        `e`.`delqty` AS `delqty` 
from    (
        `company` `c`
left join
        `endofday` `e`
on      `c`.`companyid` = `e`.`companyid`
        AND `e`.`eoddate` =
        (
        select  max(`e2`.`eoddate`) AS `max(eoddate)`
        from    `endofday` `e2` 
        where (`e2`.`companyid` = `c`.`companyid`)
        )

Answer 2

您是否尝试过使用WHERE子句自己创建视图的选择，看看会发生什么？

如果发生此问题，请对该查询运行EXPLAIN以查看发生了什么。

猜测，其中一张表中没有公司索引的索引，很可能是在最后一天。