Multi-index search vs single index search in elastic search

Question

I have a large number of entities of the same type, each having a large number of attributes and I only have these two choices to store them :

1. Storing each item as an in an index and perform multi-index search
2. Storing all of enties in a single index and search only 1 index.

Generally i want a comparison between time complexity of searching "n" entities with "m" features in each of the above cases !

Answer 1

The answer lies within the Elasticsearch documentation:

Searching 1 index of 50 shards is exactly equivalent to searching 50 indices with 1 shard each: both search requests hit 50 shards.

If you wish to learn about how shards are allocated on your nodes and how they interact with your index setup, I would suggest this stackoverflow question as well as the Elasticsearch documentation for scaling.