Index Stores

Index stores contains lightweight index metadata (i.e. additional state information created when building an index).

See the API Reference for more details.

Simple Index Store

By default, LlamaIndex uses a simple index store backed by an in-memory key-value store. They can be persisted to (and loaded from) disk by calling index_store.persist() (and SimpleIndexStore.from_persist_path(...) respectively).

MongoDB Index Store

Similarly to document stores, we can also use MongoDB as the storage backend of the index store.

from import MongoIndexStore

# create (or load) index store
index_store = MongoIndexStore.from_uri(uri="<mongodb+srv://...>")

# create storage context
storage_context = StorageContext.from_defaults(index_store=index_store)

# build index
index = GPTVectorStoreIndex(nodes, storage_context=storage_context)

# or alternatively, load index
index = load_index_from_storage(storage_context)

Under the hood, MongoIndexStore connects to a fixed MongoDB database and initializes new collections (or loads existing collections) for your index metadata.

Note: You can configure the db_name and namespace when instantiating MongoIndexStore, otherwise they default to db_name="db_docstore" and namespace="docstore".

Note that it’s not necessary to call storage_context.persist() (or index_store.persist()) when using an MongoIndexStore since data is persisted by default.

You can easily reconnect to your MongoDB collection and reload the index by re-initializing a MongoIndexStore with an existing db_name and collection_name.