# dokumentasi Django 2.2.9.dev20191202104323

# Acuan index model

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.

Mengacu pengindeksan siap-pakai

Pengindeksan ditentukan dalam `django.db.models.indexes`, tetapi untuk kenyamanan mereka diimpor kedalam `django.db.models`. Kebiasaan standar untuk digunakan `from django.db import models` dan mengacu ke pengindeksan sebagai `models.<IndexClass>`.

## Pilihan `Index`

class `Index`(fields=(), name=None, db_tablespace=None, opclasses=(), condition=None)

  Membuat sebuah index (B-tree) dalam basisdata.

### `fields`

`Index.``fields`

Sebuah list atau tuple dari nama dari bidang-bidang dimana indeks diharapkan.

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.

Changed in Django 2.1:

Versi terlama tidak menerima sebuah tuple.

### `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 (_).

Partial indexes in abstract base classes

You must always specify a unique name for an index. As such, you cannot normally specify a partial index on an abstract base class, since the `Meta.indexes` option is inherited by subclasses, with exactly the same values for the attributes (including `name`) each time. Instead, specify the `indexes` option on subclasses directly, providing a unique name for each index.

### `db_tablespace`

`Index.``db_tablespace`

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.

lihat juga

Untuk daftar dari index khusus-PostgreSQL, lihat `django.contrib.postgres.indexes`.

### `opclasses`

`Index.``opclasses`

New in Django 2.2.

The names of the PostgreSQL operator classes to use for this index. If you require a custom operator class, you must provide one for each field in the index.

For example, `GinIndex(name='json_index', fields=['jsonfield'], opclasses=['jsonb_path_ops'])` creates a gin index on `jsonfield` using `jsonb_path_ops`.

`opclasses` are ignored for databases besides PostgreSQL.

`Index.name` is required when using `opclasses`.

### `condition`

`Index.``condition`

New in Django 2.2.

If the table is very large and your queries mostly target a subset of rows, it may be useful to restrict an index to that subset. Specify a condition as a `Q`. For example, `condition=Q(pages__gt=400)` indexes records with more than 400 pages.

`Index.name` is required when using `condition`.

Restrictions on PostgreSQL

PostgreSQL requires functions referenced in the condition to be marked as IMMUTABLE. Django doesn't validate this but PostgreSQL will error. This means that functions such as Fungsi tanggal and `Concat` aren't accepted. If you store dates in `DateTimeField`, comparison to `datetime` objects may require the `tzinfo` argument to be provided because otherwise the comparison could result in a mutable function due to the casting Django does for lookups.

Restrictions on SQLite

SQLite imposes restrictions on how a partial index can be constructed.

Oracle

Oracle does not support partial indexes. Instead, partial indexes can be emulated using functional indexes. Use a migration to add the index using `RunSQL`.

MySQL and MariaDB

The `condition` argument is ignored with MySQL and MariaDB as neither supports conditional indexes.