How to migrate the queries having core-across join and json.facet to SolrCloud

[Yasufumi Mizoguchi <ya...@gmail.com>]

Hi, community.

We are trying to migrate from single Solr instance to SolrCloud with Solr
7.4.0 due to the increase of documents.
We have some join query running on current Solr, and need to migrate these
because join
queries has some restrictions when running on SolrCloud.
(We cannot use custom document routing and do not think integrate cores.)

Almost all join queries has migrate to those with StreamingExpressions, but
I am struggling
to migrate queries having both core-across join and lots of json.facet
parameters...

So, I want to know how to migrate from the queries having both core-across
join and multiple
json.facet params to those can run on SolrCloud.

query example)
http://localhost:8983/solr/books/select?q=*:*&fq={!join from=id
to=author_id fromIndex=authors
v=name:Cheng}&json.facet={"category":{"sort":"index","facet_count":"unique(author_id)"},"field":"category","limit":10,"offset":0,"mincount":1,"type":"terms",
(Similar json.facet params)
}

2 cores(books & authors) are both split into 3 shards.

Any insight would be greatly appreciated.

Thanks,
Yasufumi.