查询缓存（一）

1.查询缓存 在使用外链接进行查询时须要注意查询缓存的使用    hibernate的xml配置文件，当一对多中配置抓取策略为join时        <set inverse="true" access="field" name="childern" fetch="join" cascade="save-update,persist" >       <key column="PID"/>       <one-to-many class="com.going.platform.model.Organization"/>     </set>            String hsql=" from Organization  porg left outer join fetch porg.childern as corg ";    List<Organization> results=super.getSession().createQuery(hsql).setCacheable(true).list();    进行查询时  第一次查询会使用外链接的方式来进行查询，查询的sql语句       select         this_.ID as ID0_1_,         this_.ORGANIZATION_NAME as ORGANIZA2_0_1_,         this_.ORGANIZATION_SN as ORGANIZA3_0_1_,         this_.DESCRIPTION as DESCRIPT4_0_1_,         this_.PID as PID0_1_,         this_.ORGANIZATION_TEL as ORGANIZA6_0_1_,         this_.ORDER_NUM as ORDER7_0_1_,         this_.PERSON_ID as PERSON8_0_1_,         childern2_.PID as PID3_,         childern2_.ID as ID3_,         childern2_.ID as ID0_0_,         childern2_.ORGANIZATION_NAME as ORGANIZA2_0_0_,         childern2_.ORGANIZATION_SN as ORGANIZA3_0_0_,         childern2_.DESCRIPTION as DESCRIPT4_0_0_,         childern2_.PID as PID0_0_,         childern2_.ORGANIZATION_TEL as ORGANIZA6_0_0_,         childern2_.ORDER_NUM as ORDER7_0_0_,         childern2_.PERSON_ID as PERSON8_0_0_     from         g_organization this_     left outer join         g_organization childern2_             on this_.ID=childern2_.PID                但配置了查询缓存 第二次点击时 则会产生以下sql语句           select         organizati0_.ID as ID0_1_,         organizati0_.ORGANIZATION_NAME as ORGANIZA2_0_1_,         organizati0_.ORGANIZATION_SN as ORGANIZA3_0_1_,         organizati0_.DESCRIPTION as DESCRIPT4_0_1_,         organizati0_.PID as PID0_1_,         organizati0_.ORGANIZATION_TEL as ORGANIZA6_0_1_,         organizati0_.ORDER_NUM as ORDER7_0_1_,         organizati0_.PERSON_ID as PERSON8_0_1_,         childern1_.PID as PID3_,         childern1_.ID as ID3_,         childern1_.ID as ID0_0_,         childern1_.ORGANIZATION_NAME as ORGANIZA2_0_0_,         childern1_.ORGANIZATION_SN as ORGANIZA3_0_0_,         childern1_.DESCRIPTION as DESCRIPT4_0_0_,         childern1_.PID as PID0_0_,         childern1_.ORGANIZATION_TEL as ORGANIZA6_0_0_,         childern1_.ORDER_NUM as ORDER7_0_0_,         childern1_.PERSON_ID as PERSON8_0_0_     from         g_organization organizati0_     left outer join         g_organization childern1_             on organizati0_.ID=childern1_.PID     where         organizati0_.ID=? Hibernate:     select         organizati0_.ID as ID0_1_,         organizati0_.ORGANIZATION_NAME as ORGANIZA2_0_1_,         organizati0_.ORGANIZATION_SN as ORGANIZA3_0_1_,         organizati0_.DESCRIPTION as DESCRIPT4_0_1_,         organizati0_.PID as PID0_1_,         organizati0_.ORGANIZATION_TEL as ORGANIZA6_0_1_,         organizati0_.ORDER_NUM as ORDER7_0_1_,         organizati0_.PERSON_ID as PERSON8_0_1_,         childern1_.PID as PID3_,         childern1_.ID as ID3_,         childern1_.ID as ID0_0_,         childern1_.ORGANIZATION_NAME as ORGANIZA2_0_0_,         childern1_.ORGANIZATION_SN as ORGANIZA3_0_0_,         childern1_.DESCRIPTION as DESCRIPT4_0_0_,         childern1_.PID as PID0_0_,         childern1_.ORGANIZATION_TEL as ORGANIZA6_0_0_,         childern1_.ORDER_NUM as ORDER7_0_0_,         childern1_.PERSON_ID as PERSON8_0_0_     from         g_organization organizati0_     left outer join         g_organization childern1_             on organizati0_.ID=childern1_.PID     where         organizati0_.ID=?                 我的认为是，hibernate中会得出拥有子节点的数据id、，而后根据Id进行外链接进行查询       但若是取消查询缓存的话 每次都会调用同一语句       select         this_.ID as ID0_1_,         this_.ORGANIZATION_NAME as ORGANIZA2_0_1_,         this_.ORGANIZATION_SN as ORGANIZA3_0_1_,         this_.DESCRIPTION as DESCRIPT4_0_1_,         this_.PID as PID0_1_,         this_.ORGANIZATION_TEL as ORGANIZA6_0_1_,         this_.ORDER_NUM as ORDER7_0_1_,         this_.PERSON_ID as PERSON8_0_1_,         childern2_.PID as PID3_,         childern2_.ID as ID3_,         childern2_.ID as ID0_0_,         childern2_.ORGANIZATION_NAME as ORGANIZA2_0_0_,         childern2_.ORGANIZATION_SN as ORGANIZA3_0_0_,         childern2_.DESCRIPTION as DESCRIPT4_0_0_,         childern2_.PID as PID0_0_,         childern2_.ORGANIZATION_TEL as ORGANIZA6_0_0_,         childern2_.ORDER_NUM as ORDER7_0_0_,         childern2_.PERSON_ID as PERSON8_0_0_     from         g_organization this_     left outer join         g_organization childern2_             on this_.ID=childern2_.PID     来进行查询。。。。     得出结论就是在使用外链接时，应该注意到并非全部条件不会变化的sql语句，使用查询缓存的命中率就会高