The ObjectIndex Class

The ObjectIndex class is one that allows for the indexing of arbitrary Python objects. As such, it is quite flexible and applicable to a wide-range of use cases. As examples:

• Use an ObjectIndex to index Tool objects to then be used by an agent.

• Use an ObjectIndex to index a SQLTableSchema objects

To construct an ObjectIndex, we require an index as well as another abstraction, namely ObjectNodeMapping. This mapping, as its name suggests, provides the means to go between node and the associated object, and vice versa. Alternatively, there exists a from_objects() class method, that can conveniently construct an ObjectIndex from a set of objects.

In this notebook, we’ll quickly cover how you can build an ObjectIndex using a SimpleObjectNodeMapping.

from llama_index import VectorStoreIndex
from llama_index.objects import ObjectIndex, SimpleObjectNodeMapping

# some really arbitrary objects
obj1 = {"input": "Hey, how's it going"}
obj2 = ["a", "b", "c", "d"]
obj3 = "llamaindex is an awesome library!"
arbitrary_objects = [obj1, obj2, obj3]

# object-node mapping
obj_node_mapping = SimpleObjectNodeMapping.from_objects(arbitrary_objects)
nodes = obj_node_mapping.to_nodes(arbitrary_objects)

# object index
object_index = ObjectIndex(
    index=VectorStoreIndex(nodes=nodes), object_node_mapping=obj_node_mapping
)

As a retriever

With the object_index in hand, we can use it as a retriever, to retrieve against the index objects.

object_retriever = object_index.as_retriever(similarity_top_k=1)
object_retriever.retrieve("llamaindex")

['llamaindex is an awesome library!']

Persisting ObjectIndex

When it comes to persisting the ObjectIndex, we have to handle both the index as well as the object-node mapping. Persisting the index is straightforward and can be handled by usual means (e.g., see this guide). However, it’s a bit of a different story when it comes to persisting the ObjectNodeMapping. Since we’re indexing aribtrary Python objects with the ObjectIndex, it may be the case (and perhaps more often than we’d like), that the arbitrary objects are not serializable. In those cases, you can persist the index, but the user would have to maintain a way to re-construct the ObjectNodeMapping to be able to re-construct the ObjectIndex. For convenience, there are the persist and from_persist_dir methods on the ObjectIndex that will attempt to persist and load a previously saved ObjectIndex, respectively.

Happy example

# persist to disk (no path provided will persist to the default path ./storage)
object_index.persist()

# re-loading (no path provided will attempt to load from the default path ./storage)
reloaded_object_index = ObjectIndex.from_persist_dir()

reloaded_object_index._object_node_mapping.obj_node_mapping

{7981070310142320670: {'input': "Hey, how's it going"},
 -5984737625581842527: ['a', 'b', 'c', 'd'],
 -8305186196625446821: 'llamaindex is an awesome library!'}

object_index._object_node_mapping.obj_node_mapping

{7981070310142320670: {'input': "Hey, how's it going"},
 -5984737625581842527: ['a', 'b', 'c', 'd'],
 -8305186196625446821: 'llamaindex is an awesome library!'}

Example of when it doesn’t work

from llama_index.tools.function_tool import FunctionTool
from llama_index.indices.list.base import SummaryIndex
from llama_index.objects import SimpleToolNodeMapping


def add(a: int, b: int) -> int:
    """Add two integers and returns the result integer"""
    return a + b


def multiply(a: int, b: int) -> int:
    """Multiple two integers and returns the result integer"""
    return a * b


multiply_tool = FunctionTool.from_defaults(fn=multiply)
add_tool = FunctionTool.from_defaults(fn=add)

object_mapping = SimpleToolNodeMapping.from_objects([add_tool, multiply_tool])
object_index = ObjectIndex.from_objects(
    [add_tool, multiply_tool], object_mapping
)

# trying to persist the object_mapping directly will raise an error
object_mapping.persist()

---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
Cell In[4], line 2
      1 # trying to persist the object_mapping directly will raise an error
----> 2 object_mapping.persist()

File ~/Projects/llama_index/llama_index/objects/tool_node_mapping.py:47, in BaseToolNodeMapping.persist(self, persist_dir, obj_node_mapping_fname)
     43 def persist(
     44     self, persist_dir: str = ..., obj_node_mapping_fname: str = ...
     45 ) -> None:
     46     """Persist objs."""
---> 47     raise NotImplementedError("Subclasses should implement this!")

NotImplementedError: Subclasses should implement this!

# try to persist the object index here will throw a Warning to the user
object_index.persist()

/var/folders/0g/wd11bmkd791fz7hvgy1kqyp00000gn/T/ipykernel_77363/46708458.py:2: UserWarning: Unable to persist ObjectNodeMapping. You will need to reconstruct the same object node mapping to build this ObjectIndex
  object_index.persist()

In this case, only the index has been persisted. In order to re-construct the ObjectIndex as mentioned above, we will need to manually re-construct ObjectNodeMapping and supply that to the ObjectIndex.from_persist_dir method.

reloaded_object_index = ObjectIndex.from_persist_dir(
    object_node_mapping=object_mapping  # without this, an error will be thrown
)