Getting trouble with prefix clause for an ArcObjects Java query filter

Question

I'm using ArcObjects/Java for ArcGIS 10.2.2 and I'm trying to get unique values of a field for a feature class.

Here's my current code:

List<String> values = new ArrayList<String>();

int fieldId = featureClass.findField(fieldName);

IQueryFilter queryFilter = new QueryFilter();
queryFilter.setWhereClause(whereClause);

((IQueryFilterDefinition2)queryFilter).setPrefixClause("DISTINCT " + fieldName);

IFeatureCursor cursor = featureClass.search(queryFilter, false);
IFeature feature = null;

while((feature = cursor.nextFeature()) != null) {
    values.add((String)feature.getValue(fieldId));
}

Cleaner.release(cursor);
return values;

In theory, by using the 'prefix clause', the SQL statement should be SELECT DISTINCT field FROM ... WHERE ... but when I execute this code, I'm getting an:

AutomationException : An invalid SQL statement was used. [SELECT DISTINCT CLASS_ADM * FROM TRONCON_ROUTE]

.

The problem is this * after the DISTINCT clause that shouldn't be here.

I tried to set subFields to nothing like:

queryFilter.setSubFields("");

or

queryFilter.setSubFields(null);

but this doesn't solve the problem.

I also tried to use IDataStatistics.getUniqueValues but it returns a deprecated type IEnumVARIANT that I don't know how to use..

Any idea to get that working?

Answer 1

I just found the solution (several minutes after..).

Subfields have to be set to the fieldName:

queryFilter.setSubFields(fieldName);

and it works very fast!