CODEWITHSUNDEEP
mongodbpymongo
LostInTheFrequencyDomain
LostInTheFrequencyDomain

Reputation: 1147

When to ensure_index usage in mongodb

I have a mongo db collection that is updated (a new record is added) once a second. Will it suffice to call ensure_index ONCE on the index attribute or do I have to call it repeatedly - for example after each document is added?

I understand that ensure_index looks at the last time it was invoked and potentially re-indexes the collection. What I fail to understand is why this should be necessary in my case ( or rather I don't know if this is necessary in my case). If the order of indexing or index attribute is not changing over time, do I need to repeatedly call ensure_index once for each time a new document is added?

Upvotes: 0

Views: 120

Answers (2)

Sylvain Leroux
Sylvain Leroux

Reputation: 52020

PyMongo's ensure_index is not exactly the same thing as the Mongo Shell ensureIndex.

In pre-3.0 versions of PyMongo, ensure_index will try to create an index only if it is not already in the drivers's cache. That later is a a per-driver's instance in memory cache (whose TTL in user configurable). So this could lead to confusing situations where one client might drop an index, and an other client believes it still exists.

Please note that starting from 3.0, ensure_index is deprecated and you should now always use create_index instead -- and let it fail elegantly if the index is already existing.

Upvotes: 1

djaszczurowski
djaszczurowski

Reputation: 4523

You should call it just once. In fact this method is imdepotent, which means 'once you created an index on attribute(s), repeating the same endureIndex will have no effect'

Upvotes: 1

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