I also got this exception before and in order to avoid reindexing TB's of data, had to resort to grouping via streaming expressions, which has its ups and downs. If it's technically infeasible to substitute docValues for this purpose (when useDocValuesAsStored:true), it would be nice if it was documented in "grouping" feature or advised in general schema design pages to make unique ID's always stored:true.
-ufuk yilmaz ________________________________ From: rajani m <rajinima...@gmail.com> Sent: Wednesday, February 7, 2024 3:18 AM To: solr-user <solr-u...@lucene.apache.org> Subject: Group by query reports null pointer when unique key is not stored Hi Solr Users, Group by query is failing with the following error message. It looks like TopGroupsResultTransformer.java <https://github.com/apache/solr/blob/main/solr/core/src/java/org/apache/solr/search/grouping/distributed/shardresultserializer/TopGroupsResultTransformer.java#L237C24-L237C40> retrieveDocument method is fetching doc based on id is calling a stored field visitor method. I tried setting the "id" field to use doc values as they are enabled "useDocValuesAsStored:true" but this didn't help. Any alternative? Would you call this a bug or improvement? Error message - java.lang.NullPointerException: Cannot invoke "org.apache.lucene.index.IndexableField.stringValue()" because "f" is null => java.lang.NullPointerException: Cannot invoke "org.apache.lucene.index.IndexableField.stringValue()" because "f" is null at org.apache.solr.schema.FieldType.toExternal(FieldType.java:378) java.lang.NullPointerException: Cannot invoke "org.apache.lucene.index.IndexableField.stringValue()" because "f" is null at org.apache.solr.schema.FieldType.toExternal(FieldType.java:378) ~[?:?] at org.apache.solr.search.grouping.distributed.shardresultserializer.TopGroupsResultTransformer.serializeTopGroups(TopGroupsResultTransformer.java:238) ~[?:?]
