>For funnel analysis, it’s not feasible to use this data model for getting back a summary of the funnel steps and the sessions matching it, since there’s no option in Solr to run a recursive query, which would allow to go over each session and check if it’s a match for the funnel.

I don't think this approach scales, even in an environment that supports recursive queries like PostgreSQL.

The more scalable approach would be to use either a commercial database systems with explicit support for pattern matching or encode conversion path as a string (ex: "top page -> product page with SKU=1337 -> Purchase" becomes "T_SKU1337_P") and use REGEX/GROUP BY.

In all cases, this sounds like a suboptimal use case for either Solr or Elasticsearch.