CODEWITHSUNDEEP
pythonmongodbpython-2.7pymongo
Nyxynyx
Nyxynyx

Reputation: 63619

PyMongo create_index only if it does not exist

In a Python script using PyMongo, an index is created for a collection using the line

myCollection.create_index('Datetime', unique=True)

However this throws an error the next time the script is executed because the index already exist.

Question: Is there a way to check for the existance of an index before deciding whether to call create_index?

Upvotes: 19

Views: 10862

Answers (3)

kundan
kundan

Reputation: 1288

This might work:

def ensure_index(conn, index):
    """
    Creates the index if it does not exist.
    Input Args:
        conn: MongoClient object, created using uri.
        index: List of index tuples. Example:
            [('age', pymongo.DESCENDING), ('sex', pymongo.ASCENDING)]
    """
    index = index or []
    index_str = '_'.join(
        map(lambda x: '%s_%s' %(x[0], x[1]), index)
    )

    indexes = conn.index_information().keys()
    if index_str and index_str not in indexes:
        conn.create_index(index, background=True)

Upvotes: 1

Victor Deplasse
Victor Deplasse

Reputation: 698

In PyMongo 3.6.0 and later, calling create_index will not recreate the index if it already exists and will not throw an error. The index creation will just be ignored if the index already exists.

Upvotes: 23

alecxe
alecxe

Reputation: 473813

You can use index_information() method:

Get information on this collection’s indexes.

Returns a dictionary where the keys are index names (as returned by create_index()) and the values are dictionaries containing information about each index.

index_name = 'Datetime'
if index_name not in myCollection.index_information():
    myCollection.create_index(index_name, unique=True)

There is also list_indexes() method which can also be used to solve it, but the output format is not that convenient as in case of index_information().

And, there is that ensure_index() method, that looks exactly what you are asking about, but this method is now deprecated.

Upvotes: 16

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