PostgreSQL specific lookups¶
Trigram similarity¶
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
and activate the pg_trgm extension on PostgreSQL. You can
install the extension using the
TrigramExtension migration
operation.
The trigram_similar lookup can be used on
CharField and TextField:
>>> City.objects.filter(name__trigram_similar="Middlesborough")
['<City: Middlesbrough>']
Unaccent¶
The unaccent lookup allows you to perform accent-insensitive lookups using
a dedicated PostgreSQL extension.
This lookup is implemented using Transform, so it
can be chained with other lookup functions. To use it, you need to add
'django.contrib.postgres' in your INSTALLED_APPS and activate
the unaccent extension on PostgreSQL. The
UnaccentExtension migration
operation is available if you want to perform this activation using migrations).
The unaccent lookup can be used on
CharField and TextField:
>>> 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.
