Hibernate的Projections.countDistinct产生意外结果 [英] Projections.countDistinct with Hibernate produces unexpected result

问题描述

我有以下代码

Criteria criteria = this.getCriteriaForClass(DeviceListItem.class);
Projection rowCountProjection = Projections.countDistinct("color");
criteria.setProjection(rowCountProjection);
int rowCount = ((Long) criteria.uniqueResult()).intValue();
return rowCount;

，其目的是为名为"color"的字段找出具有不同值的行数.问题是

, whose purpose is to find out the number of rows with different values for the field named "color". The problem is that

Projections.countDistinct("color");

返回与

Projections.count("color");

即使在数据库视图中有多个具有相同颜色的行.将Criteria对象转换为SQL时，我看到Hibernate生成的SQL是

even though there are multiple rows with same color in the database view. When converting the Criteria object to SQL, I see that the SQL produced by Hibernate is

select count(this_.COLOR) as y0_ from DEVICESLIST_VIEW this_ where 1=1

我希望是

select count(distinct this_.COLOR) as y0_ from DEVICESLIST_VIEW this_ where 1=1

为什么它不能按预期工作，并且有一些补救措施?不幸的是，在这种情况下，我没有选择使用HQL.

Why doesn't it work like expected and is there some remedy? Unfortunately I have no option to use HQL in this case.

推荐答案

这是一个错误，已在3.5.2中修复: HHH-4957 .

It's a bug, fixed in 3.5.2: HHH-4957.

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