Scale function is taking longer in solr 7.4 than it was in solr 6.6

I recently upgraded Solr from version 6.6 to 7.4 and noticed that my queries are now taking longer to return results. Below is an example of the query that I am using:

select?wt=json&timeAllowed=30000&qq=(_text_%3Aattendance+OR+_text_%3Ameeting+OR+_text_%3Aminutes)&boost=sum(product(ceil(min(def(query(%24qq)%2C0)%2C1))%2C-1)%2C1.05)&boost=scale(log(sum(boost%2C1))%2C1%2C5)&boost=sum(product(ceil(min(def(query(%24qqa)%2C0)%2C1))%2C.50)%2C.50)&boost=sum(product(ceil(min(def(query(%24qqb)%2C0)%2C1))%2C.95)%2C.05)&defType=synonym_edismax&df=_text_&lowercaseOperators=true&mm=100%25&pf2=title%5E100&pf3=title%5E100&pf=content%5E75+title%5E100+_text_%5E30+_url_%5E100&ps=3&qs=2&fq=subcollection%3Amy_collection&qf=content%5E75+title%5E100+_text_%5E30+_url_%5E100&spellcheck.accuracy=0.7&spellcheck.count=0&spellcheck.dictionary=default&spellcheck.maxCollations=4&spellcheck=true&stopwords=true&synonyms=true&f._dc.subject_.facet.prefix=n2id&qqa=%7B!type%3Ddismax+qf%3D_textns_+v%3D%24q%7D&qqb=%7B!type%3Ddismax+qf%3D_textnscs_+v%3D%24q%7D&q=test&json.wrf=jQuery11130010370120476464129_1540566295961&_=1540566295962&fl=title

So the above query was working fine in version 6.6 and returned results within 30 seconds (usually under 10 seconds), but the same query in version 7.4 is taking longer than 30 seconds to return results. I was playing with all the query parameters and found that if I removed "&boost=scale(log(sum(boost%2C1))%2C1%2C5)" from the query, then the results were coming back in the expected timeframe (less than 30 seconds). I've done some research to see if anyone has experienced anything similar, but found nothing. Also, I didn't find anything in regards to the new version of solr making changes to the scale function.

 

So has anyone else experienced this? My initial thought was that the queries were taking longer because it is doing all the calculations, including the scaling, at query time. Am I right on that? I'm still new to Solr (only 3 months in) and could use any advice you guys have to offer. Thanks in advance!

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