The attachment type allows to index different "attachment" type field (encoded as base64), for example, Microsoft Office formats, open document formats, ePub, HTML, and so on (full list can be found here).

The attachment type is provided as a plugin extension. The plugin is a simple zip file that can be downloaded and placed under $ES_HOME/plugins location. It will be automatically detected and the attachment type will be added.

Note, the attachment type is experimental.

Using the attachment type is simple, in your mapping JSON, simply set a certain JSON element as attachment, for example:

{
    "person" : {
        "properties" : {
            "my_attachment" : { "type" : "attachment" }
        }
    }
}

In this case, the JSON to index can be:

{
    "my_attachment" : "... base64 encoded attachment ..."
}

Or it is possible to use more elaborated JSON if content type or resource name need to be set explicitly:

{
    "my_attachment" : {
        "_content_type" : "application/pdf",
        "_name" : "resource/name/of/my.pdf",
        "content" : "... base64 encoded attachment ..."
    }
}

The attachment type not only indexes the content of the doc, but also automatically adds meta data on the attachment as well (when available). The metadata supported are: date, title, author, and keywords. They can be queried using the "dot notation", for example: my_attachment.author.

Both the meta data and the actual content are simple core type mappers (string, date, …​), thus, they can be controlled in the mappings. For example:

{
    "person" : {
        "properties" : {
            "file" : {
                "type" : "attachment",
                "fields" : {
                    "file" : {"index" : "no"},
                    "date" : {"store" : true},
                    "author" : {"analyzer" : "myAnalyzer"}
                }
            }
        }
    }
}

In the above example, the actual content indexed is mapped under fields name file, and we decide not to index it, so it will only be available in the _all field. The other fields map to their respective metadata names, but there is no need to specify the type (like string or date) since it is already known.

The plugin uses Apache Tika to parse attachments, so many formats are supported, listed here.