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Determine if Criteria will produce a query with joins

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oregontarheel

Post subject: Determine if Criteria will produce a query with joins

Posted: Mon Mar 09, 2009 8:28 pm

Newbie

Joined: Fri Apr 13, 2007 12:25 pm
Posts: 17

Does anybody know of a reliable way to determine if a Criteria's query plan will contain joins?

I can use the CriteriaImpl.iterateSubcriteria to check for the existence of a sub-criteria, but there's also a scenario in which there are associations with a JOIN-based FetchMode, which can be specified at runtime or in the SessionFactory config.

I would like to be able to inspect a regular Criteria (or DetachedCriteria) object to determine whether it's going to be joined, as this has a bearing on how the resulting query's limit clause should be applied for paging.

Thanks in advance.

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oregontarheel

Post subject:

Posted: Mon Mar 09, 2009 9:33 pm

Newbie

Joined: Fri Apr 13, 2007 12:25 pm
Posts: 17

For anyone who might be interested, I was able to solve the problem like this. Anyone see any glaring problems? It seems to run pretty quickly on my domain model, but I could imagine this causing problems if you had a bunch of classes or classes having tons of persistent properties.

Code:

private boolean hasSubCriteria(Criteria c, Session s){
       CriteriaImpl impl = (CriteriaImpl) c;
       if(impl.iterateSubcriteria().hasNext()) return true;
       else return false;
}
    
private boolean hasFetchJoins(Criteria c, Session s){
       CriteriaImpl impl = (CriteriaImpl) c;
       Map<String,ClassMetadata> metaMap = (Map<String,ClassMetadata>) s.getSessionFactory().getAllClassMetadata();
       for(String persistentClassName : metaMap.keySet()){
          String[] props = metaMap.get(persistentClassName).getPropertyNames();
          for(int i=0; i<props.length; i++){
              if(FetchMode.JOIN.equals(impl.getFetchMode(props[i]))) return true;
          }
       }
       return false;
}

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mars1412

Post subject: Re: Determine if Criteria will produce a query with joins

Posted: Wed Aug 12, 2009 4:06 am

Beginner

Joined: Tue Nov 06, 2007 5:13 am
Posts: 28

the problem I see here is, that someone can set an explicit fetch on the criteria

Code:

criteria.setFetchMode()

your logic would not detect this - and it seems very difficult to get this information from the criteria that you have, because there is no way to directly access the fetchModes-map from CriteriaImpl

so what you could do about this:
* use reflection to access the private member
* iterate over all possible fetch-joins (using the info from the metadata) and find out if any of these exist by calling CriteriaImpl.getFetchMode()

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