Re: Difference in fieldLengh and avgFieldLength in Solr 6.6 vs Solr 7.1
Shoot in the dark, I have not double checked in details but :
With Solr 7.x
"Index-time boosts have been removed from Lucene, and are no longer
available from Solr. If any boosts are provided, they will be ignored by the
indexing chain. As a replacement, index-time scoring factors should be
indexed in a separate field and combined with the query score using a
function query. See the section Function Queries for more information."
Are you using index time boost by any chance ?
If I remember correctly the Norms stored in the segment were affected by the
field length and index time boost.