Elasticsearch DSL

Elasticsearch DSL is a high-level library whose aim is to help with writing and running queries against Elasticsearch. It is built on top of the official low-level client (elasticsearch-py).

It provides a more convenient and idiomatic way to write and manipulate queries. It stays close to the Elasticsearch JSON DSL, mirroring its terminology and structure. It exposes the whole range of the DSL from Python either directly using defined classes or a queryset-like expressions.

It also provides an optional wrapper for working with documents as Python objects: defining mappings, retrieving and saving documents, wrapping the document data in user-defined classes.

To use the other Elasticsearch APIs (eg. cluster health) just use the underlying client.

Compatibility

The library is compatible with all Elasticsearch versions since 1.x but you have to use a matching major version:

For Elasticsearch 5.0 and later, use the major version 5 (5.x.y) of the library.

For Elasticsearch 2.0 and later, use the major version 2 (2.x.y) of the library.

For Elasticsearch 1.0 and later, use the major version 0 (0.x.y) of the library.

The recommended way to set your requirements in your setup.py or requirements.txt is:

# Elasticsearch 5.x
elasticsearch-dsl>=5.0.0,<6.0.0

# Elasticsearch 2.x
elasticsearch-dsl>=2.0.0,<3.0.0

# Elasticsearch 1.x
elasticsearch-dsl<2.0.0

The development is happening on master, 2.x, and 1.x branches, respectively.

Search Example

Let's have a typical search request written directly as a dict:

from elasticsearch import Elasticsearch
client = Elasticsearch()

response = client.search(
    index="my-index",
    body={
      "query": {
        "bool": {
          "must": [{"match": {"title": "python"}}],
          "must_not": [{"match": {"description": "beta"}}],
          "filter": [{"term": {"category": "search"}}]
        }
      },
      "aggs" : {
        "per_tag": {
          "terms": {"field": "tags"},
          "aggs": {
            "max_lines": {"max": {"field": "lines"}}
          }
        }
      }
    }
)

for hit in response['hits']['hits']:
    print(hit['_score'], hit['_source']['title'])

for tag in response['aggregations']['per_tag']['buckets']:
    print(tag['key'], tag['max_lines']['value'])

The problem with this approach is that it is very verbose, prone to syntax mistakes like incorrect nesting, hard to modify (eg. adding another filter) and definitely not fun to write.

Let's rewrite the example using the Python DSL:

from elasticsearch import Elasticsearch
from elasticsearch_dsl import Search

client = Elasticsearch()

s = Search(using=client, index="my-index") \
    .filter("term", category="search") \
    .query("match", title="python")   \
    .exclude("match", description="beta")

s.aggs.bucket('per_tag', 'terms', field='tags') \
    .metric('max_lines', 'max', field='lines')

response = s.execute()

for hit in response:
    print(hit.meta.score, hit.title)

for tag in response.aggregations.per_tag.buckets:
    print(tag.key, tag.max_lines.value)

As you see, the library took care of:

creating appropriate Query objects by name (eq. "match")

composing queries into a compound bool query

putting the term query in a filter context of the bool query

providing a convenient access to response data

no curly or square brackets everywhere

Persistence Example

Let's have a simple Python class representing an article in a blogging system:

from datetime import datetime
from elasticsearch_dsl import DocType, Date, Integer, Keyword, Text
from elasticsearch_dsl.connections import connections

# Define a default Elasticsearch client
connections.create_connection(hosts=['localhost'])

class Article(DocType):
    title = Text(analyzer='snowball', fields={'raw': Keyword()})
    body = Text(analyzer='snowball')
    tags = Keyword()
    published_from = Date()
    lines = Integer()

    class Meta:
        index = 'blog'

    def save(self, ** kwargs):
        self.lines = len(self.body.split())
        return super(Article, self).save(** kwargs)

    def is_published(self):
        return datetime.now() > self.published_from

# create the mappings in elasticsearch
Article.init()

# create and save and article
article = Article(meta={'id': 42}, title='Hello world!', tags=['test'])
article.body = ''' looong text '''
article.published_from = datetime.now()
article.save()

article = Article.get(id=42)
print(article.is_published())

# Display cluster health
print(connections.get_connection().cluster.health())

In this example you can see:

providing a default connection

defining fields with mapping configuration

setting index name

defining custom methods

overriding the built-in .save() method to hook into the persistence life cycle

retrieving and saving the object into Elasticsearch

accessing the underlying client for other APIs

You can see more in the persistence chapter of the documentation.

Migration from `elasticsearch-py`

You don't have to port your entire application to get the benefits of the Python DSL, you can start gradually by creating a Search object from your existing dict, modifying it using the API and serializing it back to a dict:

body = {...} # insert complicated query here

# Convert to Search object
s = Search.from_dict(body)

# Add some filters, aggregations, queries, ...
s.filter("term", tags="python")

# Convert back to dict to plug back into existing code
body = s.to_dict()

Development

Activate Virtual Environment (virtualenvs):

$ virtualenv venv
$ source venv/bin/activate

To install all of the dependencies necessary for development, run:

$ pip install -e '.[develop]'

To run all of the tests for elasticsearch-dsl-py, run:

$ python setup.py test

Alternatively, it is possible to use the run_tests.py script in test_elasticsearch_dsl, which wraps pytest, to run subsets of the test suite. Some examples can be seen below:

# Run all of the tests in `test_elasticsearch_dsl/test_analysis.py`
$ ./run_tests.py test_analysis.py

# Run only the `test_analyzer_serializes_as_name` test.
$ ./run_tests.py test_analysis.py::test_analyzer_serializes_as_name

pytest will skip tests from test_elasticsearch_dsl/test_integration unless there is an instance of Elasticsearch on which a connection can occur. By default, the test connection is attempted at localhost:9200, based on the defaults specified in the elasticsearch-py Connection class. Because running the integration tests will cause destructive changes to the Elasticsearch cluster, only run them when the associated cluster is empty. As such, if the Elasticsearch instance at localhost:9200 does not meet these requirements, it is possible to specify a different test Elasticsearch server through the TEST_ES_SERVER environment variable.

$ TEST_ES_SERVER=my-test-server:9201 ./run_tests

Documentation

Documentation is available at https://elasticsearch-dsl.readthedocs.io.

Contribution Guide

Want to hack on Elasticsearch DSL? Awesome! We have Contribution-Guide.

License

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.

marwei/elasticsearch-dsl-py