_source

The _source field is an automatically generated field that stores the actual JSON that was used as the indexed document. It is not indexed (searchable), just stored. When executing "fetch" requests, like get or search, the _source field is returned by default.

Though very handy to have around, the source field does incur storage overhead within the index. For this reason, it can be disabled. For example:

{
    "tweet" : {
        "_source" : {"enabled" : false}
    }
}

Allow to specify paths in the source that would be included / excluded when it’s stored, supporting * as wildcard annotation. For example:

{
    "my_type" : {
        "_source" : {
            "includes" : ["path1.*", "path2.*"],
            "excludes" : ["path3.*"]
        }
    }
}