Currently I upgrade Solr version from 6.1.0 to 8.5.1 and come across one issue. Query which have more ids (around 3000) and grouping is applied takes more time to execute. In Solr 6.1.0 it takes 677ms and in Solr 8.5.1 it takes 26090ms. While take reading we have same solr schema and same no. of records in both solr version.
Please refer below details for query, logs and thead dump (generate from Solr Admin while execute query).
Query : https://drive.google.com/file/d/1bavCqwHfJxoKHFzdOEt-mSG8N0fCHE-w/view
Logs and Thread dump stack trace
Solr 8.5.1 : https://drive.google.com/file/d/149IgaMdLomTjkngKHrwd80OSEa1eJbBF/view
Solr 6.1.0 : https://drive.google.com/file/d/13v1u__fM8nHfyvA0Mnj30IhdffW6xhwQ/view
To analyse further more we found that if we remove grouping field or we reduce no. of ids from query it execute fast. Is anything change in 8.5.1 version compare to 6.1.0 as in 6.1.0 even for large no. Ids along with grouping it works faster?
Can someone please help to isolate this issue.