I have ~10 different document types which share 10-15 common fields. But each document type has additional fields, 3 of them up to 30-40 additional fields. 

I was considering to use a different mapping type for each document type. But if I correctly understand how mappings work, ElasticSearch will internally use one mapping with 150-200 fields. Because no document has a value for each field, I will end up with a lot of sparse data.

According to this article ([Index vs. Type](https://www.elastic.co/blog/index-vs-type)) ElasticSearch is (was?) not very good in dealing with sparse data, so that would be an argument for having a separate index for each document type. But some document types only have very little documents, so it would be overkill to have a separate index for them.

My question: How bad are sparse documents? Or am I better off with a separate index for each type even though some indexes will only contain a few documents?