A RetroSearch Logo

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Search Query:

Showing content from https://django-elasticsearch-dsl.readthedocs.io/en/latest/fields.html below:

Fields — django-elasticsearch-dsl 7.1.1 documentation

Fields

Once again the django_elasticsearch_dsl.fields are subclasses of elasticsearch-dsl-py fields. They just add support for retrieving data from django models.

Using Different Attributes for Model Fields

Let’s say you don’t want to store the type of the car as an integer, but as the corresponding string instead. You need some way to convert the type field on the model to a string, so we’ll just add a method for it:

# models.py

class Car(models.Model):
    # ... #
    def type_to_string(self):
        """Convert the type field to its string representation
        (the boneheaded way).
        """
        if self.type == 1:
            return "Sedan"
        elif self.type == 2:
            return "Truck"
        else:
            return "SUV"

Now we need to tell our Document subclass to use that method instead of just accessing the type field on the model directly. Change the CarDocument to look like this:

# documents.py

from django_elasticsearch_dsl import Document, fields

# ... #

@registry.register_document
class CarDocument(Document):
    # add a string field to the Elasticsearch mapping called type, the
    # value of which is derived from the model's type_to_string attribute
    type = fields.TextField(attr="type_to_string")

    class Django:
        model = Car
        # we removed the type field from here
        fields = [
            'name',
            'color',
            'description',
        ]

After a change like this we need to rebuild the index with:

$ ./manage.py search_index --rebuild
Using prepare_field

Sometimes, you need to do some extra prepping before a field should be saved to Elasticsearch. You can add a prepare_foo(self, instance) method to a Document (where foo is the name of the field), and that will be called when the field needs to be saved.

# documents.py

# ... #

class CarDocument(Document):
    # ... #

    foo = TextField()

    def prepare_foo(self, instance):
        return " ".join(instance.foos)
Handle relationship with NestedField/ObjectField

For example for a model with ForeignKey relationships.

# models.py

class Car(models.Model):
    name = models.CharField()
    color = models.CharField()
    manufacturer = models.ForeignKey('Manufacturer')

class Manufacturer(models.Model):
    name = models.CharField()
    country_code = models.CharField(max_length=2)
    created = models.DateField()

class Ad(models.Model):
    title = models.CharField()
    description = models.TextField()
    created = models.DateField(auto_now_add=True)
    modified = models.DateField(auto_now=True)
    url = models.URLField()
    car = models.ForeignKey('Car', related_name='ads')

You can use an ObjectField or a NestedField.

# documents.py

from django_elasticsearch_dsl import Document, fields
from .models import Car, Manufacturer, Ad

@registry.register_document
class CarDocument(Document):
    manufacturer = fields.ObjectField(properties={
        'name': fields.TextField(),
        'country_code': fields.TextField(),
    })
    ads = fields.NestedField(properties={
        'description': fields.TextField(analyzer=html_strip),
        'title': fields.TextField(),
        'pk': fields.IntegerField(),
    })

    class Index:
        name = 'cars'

    class Django:
        model = Car
        fields = [
            'name',
            'color',
        ]
        related_models = [Manufacturer, Ad]  # Optional: to ensure the Car will be re-saved when Manufacturer or Ad is updated

    def get_queryset(self):
        """Not mandatory but to improve performance we can select related in one sql request"""
        return super(CarDocument, self).get_queryset().select_related(
            'manufacturer'
        )

    def get_instances_from_related(self, related_instance):
        """If related_models is set, define how to retrieve the Car instance(s) from the related model.
        The related_models option should be used with caution because it can lead in the index
        to the updating of a lot of items.
        """
        if isinstance(related_instance, Manufacturer):
            return related_instance.car_set.all()
        elif isinstance(related_instance, Ad):
            return related_instance.car
Field Classes

Most Elasticsearch field types are supported. The attr argument is a dotted “attribute path” which will be looked up on the model using Django template semantics (dict lookup, attribute lookup, list index lookup). By default the attr argument is set to the field name.

For the rest, the field properties are the same as elasticsearch-dsl fields.

So for example you can use a custom analyzer:

# documents.py

# ... #

html_strip = analyzer(
    'html_strip',
    tokenizer="standard",
    filter=["lowercase", "stop", "snowball"],
    char_filter=["html_strip"]
)

@registry.register_document
class CarDocument(Document):
    description = fields.TextField(
        analyzer=html_strip,
        fields={'raw': fields.KeywordField()}
    )

    class Django:
        model = Car
        fields = [
            'name',
            'color',
        ]
Available Fields

properties is a dict where the key is a field name, and the value is a field instance.

Field Mapping

Django Elasticsearch DSL maps most of the django fields appropriate Elasticsearch Field. You can find the field mapping on documents.py file in the model_field_class_to_field_class variable. If you need to change the behavior of this mapping, or add mapping for your custom field, you can do so by overwriting the classmethod get_model_field_class_to_field_class. Remember, you need to inherit django_elasticsearch_dsl.fields.DEDField for your custom field. Like following

from django_elasticsearch_dsl.fields import DEDField

class MyCustomDEDField(DEDField, ElasticsearchField):
    pass

@classmethod
def get_model_field_class_to_field_class(cls):
    field_mapping = super().get_model_field_class_to_field_class()
    field_mapping[MyCustomDjangoField] = MyCustomDEDField
Document id

The elasticsearch document id (_id) is not strictly speaking a field, as it is not part of the document itself. The default behavior of django_elasticsearch_dsl is to use the primary key of the model as the document’s id (pk or id). Nevertheless, it can sometimes be useful to change this default behavior. For this, one can redefine the generate_id(cls, instance) class method of the Document class.

For example, to use an article’s slug as the elasticsearch _id instead of the article’s integer id, one could use:

# models.py

from django.db import models

class Article(models.Model):
    # ... #

    slug = models.SlugField(
        max_length=255,
        unique=True,
    )

    # ... #


# documents.py

from .models import Article

class ArticleDocument(Document):
    class Django:
        model = Article

    # ... #

    @classmethod
    def generate_id(cls, article):
        return article.slug

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4