But in the official documentation it says :
Other than where documented, existing type and field mappings cannot be updated. Changing the mapping would mean invalidating already indexed documents. Instead, you should create a new index with the correct mappings and reindex your data into that index.
So are you saying that if a document has more fields than the mapping, it would upgrading the mapping by adding the new fields? But the existing documents don't have such fields. Would it be a problem?
Also, how about a document has a field that doesn't match the type defined in the mapping? For instance, I have a field called "day" in mapping defined as a number , but I index a document with a field called "day" that is a string?