Interesting, but if you look at the method isIndexedOrStored (QName propertyQName) of org.alfresco.solr.AlfrescoSolrDataModel class, you can see comment
by default we would index a residual property (if they have a known prefix/uri ….)
I tried to add a residual property with a known prefix, but it's still not working. I am continued to study the issue and came to the class org.alfresco.repo.solr.SOLRTrackingComponentImpl, which has a method protected Map <QName, Serializable> getProperties (Long nodeId), in which we will return the desired properties of our nodes. And there are the following comment…
Residual properties are un-indexed -> break serlialisation
Therefore before had the opportunity to index the residual field.
