Django2.0手册:Model index reference



New in Django 1.11.

Index classes ease creating database indexes. They can be added using the
Meta.indexes option. This document
explains the API references of Index which includes the index
options
.

Referencing built-in indexes

Indexes are defined in django.db.models.indexes, but for convenience
they’re imported into django.db.models. The standard convention is
to use from django.db import models and refer to the indexes as
models.<IndexClass>.

Index options¶

class Index(fields=[], name=None, db_tablespace=None)[source]

Creates an index (B-Tree) in the database.

fields¶

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.

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¶

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 (_).

db_tablespace¶

Index.db_tablespace
New in Django 2.0.

The name of the database tablespace to use for
this index. For single field indexes, if db_tablespace isn’t provided, the
index is created in the db_tablespace of the field.

If Field.db_tablespace isn’t specified (or if the index uses multiple
fields), the index is created in tablespace specified in the
db_tablespace option inside the model’s
class Meta. If neither of those tablespaces are set, the index is created
in the same tablespace as the table.

See also

For a list of PostgreSQL-specific indexes, see
django.contrib.postgres.indexes.