[hibernate-issues] [Hibernate-JIRA] Created: (HHH-4113) Support for case when ... then ... else ... end when using projections

[Dobes Vandermeer (JIRA)]

Support for case when ... then ... else ... end when using projections
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                 Key: HHH-4113
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4113
             Project: Hibernate Core
          Issue Type: New Feature
    Affects Versions: 3.3.2
            Reporter: Dobes Vandermeer
         Attachments: CaseWhenProjection.java, ConstantProjection.java

I have a colleciton of queries that are mostly the same except for one part of the condition, and I decided to convert them to using the criteria API so I didn't have to copy/paste the entire text of the query all over the place.  The only missing features were:

1. Support for case when ... then ... else ... end in the select clauses/projections
2. Support for constants in the projections

So, I added them.

There are a couple hacks in there that could be eliminated if you were willing to change the guts of the criteria system a little bit - particularly to allow projections to add '?' values to the SQL query and to make it easier to tell a projection not to emit as "as" clause.  These changes would support other compound projections such as negation, add, subtract, divide.  Why not support expressions like "sum(case when x then -y else z end)" ... ?

I thought I'd share these to benefit anyone else out there who might run into the same issue, or to serve as an example to work from if the hibernate contributors are interested in incorporating this into the core.




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