I'm using Redisearch for my project. there are different indexes in the project, such as job_idx, company_idx, article_idx and event_idx (article_idx and event_idx structure are very similar). The index is used on different pages, ex: job_idx used by Job page search, company_idx used by Company page search.
The question is on the homepage, the search engine should return result from every index, so should I call search 4 times? I think that there should be better solution for my case.
The FT.SEARCH command allows you to pass exactly one index as a parameter. So if you are already having 4 indexes, then you need to call the command 4 times.
It's typically the simplest to have one index per entity, BUT it's at the end a question how you are designing your physical data model to support your queries best. This can range from entirely separated indexes up to one single index for everything (e.g., an 'all_fields' index with a type field). The best implementation might be somewhere in the middle (very much similar to 'normalized vs. de-normalized database schema' in relational database systems).
A potential solution for you could be to create an additional index (e.g., called combined_homepage) which indexes on specific fields that are needed for the search on the homepage. This index would then enable you to do a single search.
However, this additional index would indeed need additional space. So, considering that you don't want to rethink the physical data model from scratch, you either invest into space (memory) to enable a more efficient access, or spend more for compute and network (for combining the results of the 4 queries on the client-side).
Hope this helps, even if my answer comes basically down to 'it depends' :-).
