===================== Model index reference ===================== .. module:: django.db.models.indexes .. currentmodule:: django.db.models .. versionadded:: 1.11 Index classes ease creating database indexes. They can be added using the :attr:`Meta.indexes ` option. This document explains the API references of :class:`Index` which includes the `index options`_. .. admonition:: Referencing built-in indexes Indexes are defined in ``django.db.models.indexes``, but for convenience they're imported into :mod:`django.db.models`. The standard convention is to use ``from django.db import models`` and refer to the indexes as ``models.``. ``Index`` options ================= .. class:: Index(fields=[], name=None) Creates an index (B-Tree) in the database. ``fields`` ---------- .. attribute:: Index.fields A list of the name of the fields on which the index is desired. By default, indexes are created with an ascending order for each column. To define an index with a descending order for a column, add a hyphen before the field's name. For example ``Index(fields=['headline', '-pub_date'])`` would create SQL with ``(headline, pub_date DESC)``. Index ordering isn't supported on MySQL. In that case, a descending index is created as a normal index. .. admonition:: Support for column ordering on SQLite Column ordering is supported on SQLite 3.3.0+ and only for some database file formats. Refer to the `SQLite docs `_ for specifics. ``name`` -------- .. attribute:: Index.name The name of the index. If ``name`` isn't provided Django will auto-generate a name. For compatibility with different databases, index names cannot be longer than 30 characters and shouldn't start with a number (0-9) or underscore (_). .. seealso:: For a list of PostgreSQL-specific indexes, see :mod:`django.contrib.postgres.indexes`.