---
title: "PostgreSQL specific lookups"
version: 5.2
locale: it
source: https://docs.djangoproject.com/it/5.2/ref/contrib/postgres/lookups/
canonical: https://djangodocs.dev/it/5.2/ref/contrib/postgres/lookups/
---
# PostgreSQL specific lookups

## Trigram similarity

### `trigram_similar`

The `trigram_similar` lookup allows you to perform trigram lookups,
measuring the number of trigrams (three consecutive characters) shared, using a
dedicated PostgreSQL extension. A trigram lookup is given an expression and
returns results that have a similarity measurement greater than the current
similarity threshold.

To use it, add `'django.contrib.postgres'` in your [`INSTALLED_APPS`](/it/5.2/ref/settings/#std-setting-INSTALLED_APPS)
and activate the [pg\_trgm extension](https://www.postgresql.org/docs/current/pgtrgm.html) on PostgreSQL. You can install the
extension using the
[`TrigramExtension`](/it/5.2/ref/contrib/postgres/operations/#django.contrib.postgres.operations.TrigramExtension) migration
operation.

The `trigram_similar` lookup can be used on
[`CharField`](/it/5.2/ref/models/fields/#django.db.models.CharField) and [`TextField`](/it/5.2/ref/models/fields/#django.db.models.TextField):

```pycon
>>> City.objects.filter(name__trigram_similar="Middlesborough")
['<City: Middlesbrough>']
```

### `trigram_word_similar`

The `trigram_word_similar` lookup allows you to perform trigram word
similarity lookups using a dedicated PostgreSQL extension. It can be
approximately understood as measuring the greatest number of trigrams shared
between the parameter and any substring of the field. A trigram word lookup is
given an expression and returns results that have a word similarity measurement
greater than the current similarity threshold.

To use it, add `'django.contrib.postgres'` in your [`INSTALLED_APPS`](/it/5.2/ref/settings/#std-setting-INSTALLED_APPS)
and activate the [pg\_trgm extension](https://www.postgresql.org/docs/current/pgtrgm.html) on PostgreSQL. You can install the
extension using the
[`TrigramExtension`](/it/5.2/ref/contrib/postgres/operations/#django.contrib.postgres.operations.TrigramExtension) migration
operation.

The `trigram_word_similar` lookup can be used on
[`CharField`](/it/5.2/ref/models/fields/#django.db.models.CharField) and [`TextField`](/it/5.2/ref/models/fields/#django.db.models.TextField):

```pycon
>>> Sentence.objects.filter(name__trigram_word_similar="Middlesborough")
['<Sentence: Gumby rides on the path of Middlesbrough>']
```

### `trigram_strict_word_similar`

Similar to [`trigram_word_similar`](#std-fieldlookup-trigram_word_similar), except that it forces extent
boundaries to match word boundaries.

To use it, add `'django.contrib.postgres'` in your [`INSTALLED_APPS`](/it/5.2/ref/settings/#std-setting-INSTALLED_APPS)
and activate the [pg\_trgm extension](https://www.postgresql.org/docs/current/pgtrgm.html) on PostgreSQL. You can install the
extension using the
[`TrigramExtension`](/it/5.2/ref/contrib/postgres/operations/#django.contrib.postgres.operations.TrigramExtension) migration
operation.

The `trigram_strict_word_similar` lookup can be used on
[`CharField`](/it/5.2/ref/models/fields/#django.db.models.CharField) and [`TextField`](/it/5.2/ref/models/fields/#django.db.models.TextField).

## `Unaccent`

The `unaccent` lookup allows you to perform accent-insensitive lookups using
a dedicated PostgreSQL extension.

This lookup is implemented using [`Transform`](/it/5.2/ref/models/lookups/#django.db.models.Transform), so it
can be chained with other lookup functions. To use it, you need to add
`'django.contrib.postgres'` in your [`INSTALLED_APPS`](/it/5.2/ref/settings/#std-setting-INSTALLED_APPS) and activate
the [unaccent extension on PostgreSQL](https://www.postgresql.org/docs/current/unaccent.html). The
[`UnaccentExtension`](/it/5.2/ref/contrib/postgres/operations/#django.contrib.postgres.operations.UnaccentExtension) migration
operation is available if you want to perform this activation using migrations).

The `unaccent` lookup can be used on
[`CharField`](/it/5.2/ref/models/fields/#django.db.models.CharField) and [`TextField`](/it/5.2/ref/models/fields/#django.db.models.TextField):

```pycon
>>> City.objects.filter(name__unaccent="México")
['<City: Mexico>']

>>> User.objects.filter(first_name__unaccent__startswith="Jerem")
['<User: Jeremy>', '<User: Jérémy>', '<User: Jérémie>', '<User: Jeremie>']
```

> **Warning**
>
> `unaccent` lookups should perform fine in most use cases. However, queries
> using this filter will generally perform full table scans, which can be slow
> on large tables. In those cases, using dedicated full text indexing tools
> might be appropriate.