Compound Indexes
Overview
Compound indexes hold references to multiple fields within a collection's documents, improving query and sort performance.
Sample Data
The examples in this guide use the sample_mflix.movies
collection
from the Atlas sample datasets. To learn how to create a
free MongoDB Atlas cluster and load the sample datasets, see the
Get Started with PyMongo.
Create a Compound Index
The following example creates a compound index on the type
and genre
fields:
movies.create_index([("type", pymongo.ASCENDING), ("genre", pymongo.ASCENDING)])
The following is an example of a query that uses the index created in the preceding code example:
query = { "type": "movie", "genre": "Drama" } sort = [("type", pymongo.ASCENDING), ("genre", pymongo.ASCENDING)] cursor = movies.find(query).sort(sort)
For more information, see Compound Indexes in the MongoDB Server manual.
Collation
When you create an index, you can specify a default collation for all operations you perform on fields that are included in the index.
A collation is a set of language-specific rules for string comparison, such as for letter case and accent marks.
To specify a collation, create an instance of the Collation
class or a Python dictionary.
For a list of options to pass to the Collation
constructor or include as keys in the
dictionary, see Collation in the MongoDB Server manual.
Tip
Import Collation
To create an instance of the Collation
class, you must import it from
pymongo.collation
.
To use an index with a specified collation, your operation must meet the following criteria:
The operation uses the same collation as the one specified in the index.
The operation is covered by the index that contains the collation.
The following example creates the same index as the previous example,
but with a default collation of fr_CA
:
from pymongo.collation import Collation movies.create_index([("type", pymongo.ASCENDING), ("genre", pymongo.ASCENDING)], collation=Collation(locale='fr_CA'))