Mapper Attachments Type for Elasticsearch

The mapper attachments plugin adds the attachment type to Elasticsearch using Apache Tika. 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).

In order to install the plugin, run:

bin/plugin -install elasticsearch/elasticsearch-mapper-attachments/2.4.1

You need to install a version matching your Elasticsearch version:

Elasticsearch	Attachments Plugin	Docs
master	Build from source	See below
es-1.x	Build from source	2.5.0-SNAPSHOT
es-1.4	2.4.1	2.4.1
es-1.3	2.3.2	2.3.2
es-1.2	2.2.1	2.2.1
es-1.1	2.0.0	2.0.0
es-1.0	2.0.0	2.0.0
es-0.90	1.9.0	1.9.0

To build a SNAPSHOT version, you need to build it with Maven:

mvn clean install
plugin --install mapper-attachments \ 
       --url file:target/releases/elasticsearch-mapper-attachments-X.X.X-SNAPSHOT.zip

Using mapper attachments

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

PUT /test/person/_mapping
{
    "person" : {
        "properties" : {
            "my_attachment" : { "type" : "attachment" }
        }
    }
}

In this case, the JSON to index can be:

PUT /test/person/1
{
    "my_attachment" : "... base64 encoded attachment ..."
}

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

PUT /test/person/1
{
    "my_attachment" : {
        "_content_type" : "application/pdf",
        "_name" : "resource/name/of/my.pdf",
        "_language" : "en",
        "_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
• name only available if you set _name see above
• author
• keywords
• content_type
• content_length is the original content_length before text extraction (aka file size)
• language

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:

PUT /test/person/_mapping
{
    "person" : {
        "properties" : {
            "file" : {
                "type" : "attachment",
                "fields" : {
                    "file" : {"index" : "no"},
                    "title" : {"store" : "yes"},
                    "date" : {"store" : "yes"},
                    "author" : {"analyzer" : "myAnalyzer"},
                    "keywords" : {"store" : "yes"},
                    "content_type" : {"store" : "yes"},
                    "content_length" : {"store" : "yes"},
                    "language" : {"store" : "yes"}
                }
            }
        }
    }
}

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.

Querying or accessing metadata

If you need to query on metadata fields, use the attachment field name dot the metadata field. For example:

DELETE /test
PUT /test
PUT /test/person/_mapping
{
  "person": {
    "properties": {
      "file": {
        "type": "attachment",
        "path": "full",
        "fields": {
          "content_type": {
            "type": "string",
            "store": true
          }
        }
      }
    }
  }
}
PUT /test/person/1?refresh=true
{
  "file": "IkdvZCBTYXZlIHRoZSBRdWVlbiIgKGFsdGVybmF0aXZlbHkgIkdvZCBTYXZlIHRoZSBLaW5nIg=="
}
GET /test/person/_search
{
  "fields": [ "file.content_type" ], 
  "query": {
    "match": {
      "file.content_type": "text plain"
    }
  }
}

Will give you:

{
   "took": 2,
   "timed_out": false,
   "_shards": {
      "total": 5,
      "successful": 5,
      "failed": 0
   },
   "hits": {
      "total": 1,
      "max_score": 0.16273327,
      "hits": [
         {
            "_index": "test",
            "_type": "person",
            "_id": "1",
            "_score": 0.16273327,
            "fields": {
               "file.content_type": [
                  "text/plain; charset=ISO-8859-1"
               ]
            }
         }
      ]
   }
}

Indexed Characters

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:

PUT /test/person/1
{
    "my_attachment" : {
        "_indexed_chars" : -1,
        "_content" : "... base64 encoded attachment ..."
    }
}

Metadata parsing error handling

While extracting metadata content, errors could happen for example when parsing dates. Parsing errors are ignored so your document is indexed.

You can disable this feature by setting the index.mapping.attachment.ignore_errors setting to false.

Language Detection

By default, language detection is disabled (false) as it could come with a cost. This default value can be changed by setting the index.mapping.attachment.detect_language setting. It can also be provided on a per document indexed using the _detect_language parameter.

Note that you can force language using _language field when sending your actual document:

{
    "my_attachment" : {
        "_language" : "en",
        "_content" : "... base64 encoded attachment ..."
    }
}

Highlighting attachments

If you want to highlight your attachment content, you will need to set "store": true and "term_vector":"with_positions_offsets" for your attachment field. Here is a full script which does it:

DELETE /test
PUT /test
PUT /test/person/_mapping
{
  "person": {
    "properties": {
      "file": {
        "type": "attachment",
        "path": "full",
        "fields": {
          "file": {
            "type": "string",
            "term_vector":"with_positions_offsets",
            "store": true
          }
        }
      }
    }
  }
}
PUT /test/person/1?refresh=true
{
  "file": "IkdvZCBTYXZlIHRoZSBRdWVlbiIgKGFsdGVybmF0aXZlbHkgIkdvZCBTYXZlIHRoZSBLaW5nIg=="
}
GET /test/person/_search
{
  "fields": [], 
  "query": {
    "match": {
      "file": "king queen"
    }
  },
  "highlight": {
    "fields": {
      "file": {
      }
    }
  }
}

It gives back:

{
   "took": 9,
   "timed_out": false,
   "_shards": {
      "total": 1,
      "successful": 1,
      "failed": 0
   },
   "hits": {
      "total": 1,
      "max_score": 0.13561106,
      "hits": [
         {
            "_index": "test",
            "_type": "person",
            "_id": "1",
            "_score": 0.13561106,
            "highlight": {
               "file": [
                  "\"God Save the <em>Queen</em>\" (alternatively \"God Save the <em>King</em>\"\n"
               ]
            }
         }
      ]
   }
}

License

This software is licensed under the Apache 2 license, quoted below.

Copyright 2009-2014 Elasticsearch <http://www.elasticsearch.org>

Licensed under the Apache License, Version 2.0 (the "License"); you may not
use this file except in compliance with the License. You may obtain a copy of
the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations under
the License.