How to append index level information to documents when returning search results

Hi! Relatively simple question -- I want to append index-level information onto each document when returning those documents. I do not want to copy that information into each document (makes it harder to adjust that information if it changes). I've found out that you can use the _meta tag to add information to the index level, but now I want it to be appended onto the document when returning results from a search query.

My specific use case is: I have indices that store posts per user (indices are structured as: posts-USER_ID). I'm performing a search across all posts across all user indices (search index: posts-*), and I want to return user information with each index (that user information being a JSON object with fields like username, userColor, displayName).

I see that fields like _index and _type are index-level and returned with each document automatically. I essentially want to return a custom field as well. As said above I've been able to successfully append this user information on _meta for an index but I can't figure out how to append it to documents returned from that index (for my search results from that multi-index query).

The reason I want this is because I need user information with post information on search (to display various things, username, displayName, coloring posts in the userColor). Ideally I'd prefer not to have to perform another query for each search result to retrieve user information (for each document result, querying the user that created that post -- seems expensive). I also would not like to copy that user information in each document in an index (so under a posts-USERID index adding a creator field with user information). But that seems insanely repetitive (as the indices are already partitioned per user) and when the user updates information that is very very expensive (would have to iterate through each document in "their" index and change their information.

What do I do / help! :slight_smile:

It sounds to me like this way of indexing data could result in a large number of very small indices, which will be inefficient and scale and perform badly. I would recommend storing the user information with each post and store all user posts in a single index.