How to eliminate duplicate values in input for StoredId data connector when using RelationalDatabase data connector

[Daniel Lutz]

On one of our IdPs (V3), the attributes are stored in a relational database. We use
a RelationalDatabase data connector to get the attribute values from the database.
As some attributes are multi-valued, the result sets may contain multiple duplicate values
for the single-valued attributes.

We use a StoredId data connector to support the "eduPersonTargetedID" SAML Attribute
(we still require this in our federation).
The source attribute is the (single-valued) "swissEduPersonUniqueID" attribute. As the
values come from the relational database, the source attribute may have more than one value,
actually duplicates of a single value. We get the following warning:

WARN [net.shibboleth.idp.saml.attribute.resolver.impl.AbstractPersistentIdDataConnector:137]
- Data Connector 'myStoredId': Source attribute swissEduPersonUniqueID.withoutAttributeEncoder for connector myStoredId has more than one value, only one value is used


Is there some way to eliminate duplicate values in the source attribute
before feeding the value to the StoredId data connector?


- Daniel