Thanks, Val for the reply.
participation index consist of 80k docs and therapy index contains 9k docs with ''user_id" field in comman.
I want to know if enrichment processor scans docs 1 to 1 for user id in both indexes.
OR Enrichment processor will scan all docs present in participation index for particular "user id" in therapy index and it will enrich stored docs in new index.
If docs get 1 to 1 that is the user id of 1st doc in therapy is check with user id participation in 1 st then hardly any docs will get enriched.
Enriching process described here-Enrichment processor working fine on demo index