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](http://lucene.apache.org/tika/0.10/formats.html)).
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.
Using the attachment type is simple, in your mapping JSON, simply set a certain JSON element as attachment, for example:
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" : "yes"},
"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.
By default, `100000` characters are extracted when indexing the content. This default value can be changed by setting the `index.mapping.attachment.indexed_chars` setting. It can also be provided on a per document indexed using the `_indexed_chars` parameter. `-1` can be set to extract all text, but note that all the text needs to be allowed to be represented in memory.
Note, this feature is support since `1.3.0` version.
The plugin uses [Apache Tika](http://lucene.apache.org/tika/) to parse attachments, so many formats are supported, listed [here](http://lucene.apache.org/tika/0.10/formats.html).
