Can ES running with small ram but big docs?

Hi All,

I am working a project and I get some problems

I use ES with 1 node 1 shard and 500M of Heap size and 1.5G of ram. but there are about 1 billion docs will be index. now ES got OOM when it running with about 300 million docs.but sadly I don't have bigger ram.

So,I want to know if it's possible to config ES running with low Heap size and has no relation with docs size even search become slowly.