Integrating with Elasticsearch

ZomboDB integrates Postgres with Elasticsearch through Postgres indexes. If you don’t know much about ZomboDB, please read its tutorial before proceeding.

Installing ZomboDB extension

Since ZomboDB is a Postgres extension, you must install and activate it. Follow the official ZomboDB installation instructions.

Activating ZomboDB extension

django-zombodb provides a Django migration operation to activate ZomboDB extension on your database. To run it, please make sure your database user is a superuser:

psql -d your_database -c "ALTER USER your_database_user SUPERUSER"

Then create an empty migration on your “main” app (usually called “core” or “common”):

python manage.py makemigrations core --empty

Add the django_zombodb.operations.ZomboDBExtension operation to the migration you’ve just created:

import django_zombodb.operations

class Migration(migrations.Migration):

    dependencies = [
        ('restaurants', '0001_initial'),
    ]

    operations = [
        django_zombodb.operations.ZomboDBExtension(),
        ...
    ]

Alternatively, you can activate the extension manually with a command. But you should avoid this because you’ll need to remember to run this on production, on tests, and on the machines of all your co-workers:

psql -d django_zombodb -c "CREATE EXTENSION zombodb"

Creating an index

Imagine you have the following model:

class Restaurant(models.Model):
    name = models.TextField()
    street = models.TextField()

To integrate it with Elasticsearch, we need to add a ZomboDBIndex to it:

from django_zombodb.indexes import ZomboDBIndex

class Restaurant(models.Model):
    name = models.TextField()
    street = models.TextField()

    class Meta:
        indexes = [
            ZomboDBIndex(fields=[
                'name',
                'street',
            ]),
        ]

After that, create and run the migrations:

python manage.py makemigrations
python manage.py migrate

Warning

During the migration, ZomboDBIndex reads the value at settings.ZOMBODB_ELASTICSEARCH_URL. That means if settings.ZOMBODB_ELASTICSEARCH_URL changes after the ZomboDBIndex migration, the internal index stored at Postgres will still point to the old URL. If you wish to change the URL of an existing ZomboDBIndex, change both settings.ZOMBODB_ELASTICSEARCH_URL and issue a ALTER INDEX index_name SET (url='http://some.new.url'); (preferably inside a migrations.RunSQL in a new migration).

Now the Restaurant model will support Elasticsearch queries for both name and street fields. But to perform those searches, we need it to use the custom queryset SearchQuerySet:

from django_zombodb.indexes import ZomboDBIndex
from django_zombodb.querysets import SearchQuerySet

class Restaurant(models.Model):
    name = models.TextField()
    street = models.TextField()

    objects = models.Manager.from_queryset(SearchQuerySet)()

    class Meta:
        indexes = [
            ZomboDBIndex(fields=[
                'name',
                'street',
            ]),
        ]

Note

If you already have a custom queryset on your model, make it inherit from SearchQuerySetMixin.

Field mapping

From Elasticsearch documentation:

“Mapping is the process of defining how a document, and the fields it contains, are stored and indexed. For instance, use mappings to define:

• which string fields should be treated as full text fields.

• which fields contain numbers, dates, or geolocations.

• whether the values of all fields in the document should be indexed into the catch-all _all field.

• the format of date values.

• custom rules to control the mapping for dynamically added fields.”

If you don’t specify a mapping for your ZomboDBIndex, django-zombodb uses ZomboDB’s default mappings, which are based on the Postgres type of your model fields.

To customize mapping, specify a field_mapping parameter to your ZomboDBIndex like below:

from django_zombodb.indexes import ZomboDBIndex
from django_zombodb.querysets import SearchQuerySet

class Restaurant(models.Model):
    name = models.TextField()
    street = models.TextField()

    objects = models.Manager.from_queryset(SearchQuerySet)()

    class Meta:
        indexes = [
            ZomboDBIndex(
                fields=[
                    'name',
                    'street',
                ],
                field_mapping={
                    'name': {"type": "text",
                             "copy_to": "zdb_all",
                             "analyzer": "fulltext_with_shingles",
                             "search_analyzer": "fulltext_with_shingles_search"},
                    'street': {"type": "text",
                               "copy_to": "zdb_all",
                               "analyzer": "brazilian"},
                }
            )
        ]

Note

You probably wish to have "copy_to": "zdb_all" on your textual fields to match ZomboDB default behavior. From ZomboDB docs: “zdb_all is ZomboDB’s version of Elasticsearch’s “_all” field, except zdb_all is enabled for all versions of Elasticsearch. It is also configured as the default search field for every ZomboDB index”. For more info, read Elasticsearch docs take on the “_all” field.

Move forward to learn how to perform Elasticsearch queries through your model.