retrieve_existing_index() Defaults to "neo4j" Database for Vector Index Info Even When Data Uses Different Database

[ArghyaBanerjee30]

Checked other resources

• This is a bug, not a usage question. For questions, please use the LangChain Forum (https://forum.langchain.com/).
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Example Code

index_information = retrieve_vector_index_info(
    driver=self._driver,
    index_name=self.index_name,
    label_or_type=self.node_label,
    embedding_property=self.embedding_node_property,
    neo4j_database=self._database   # <-- Correct way
)

Error Message and Stack Trace (if applicable)

No response

Description

While using retrieve_existing_index(), we call retrieve_vector_index_info(), which expects a neo4j_database argument. However, we are not passing any database name to this function. As a result, it defaults to using the neo4j database for retrieving vector index information, regardless of which database is actually being used for the data (as specified in the config).

Code Reference:

index_information = retrieve_vector_index_info(
    driver=self._driver,
    index_name=self.index_name,
    label_or_type=self.node_label,
    embedding_property=self.embedding_node_property,
    # neo4j_database is not passed here
)

According to the docstring for retrieve_vector_index_info():

neo4j_database (Optional[str]): The name of the Neo4j database.
    If not provided, this defaults to the server's default database ("neo4j" by default)
    (see reference to documentation: https://neo4j.com/docs/operations-manual/current/database-administration/#manage-databases-default)

Issue/Impact:

• If the vector index is not present in the neo4j database, or if the nodes with the expected vector dimension exist in a different database, the function will either fail or return None.

• This can lead to inconsistencies, especially in multi-database environments where the data and the vector index may not reside in the default neo4j database.

Expected Behavior:

retrieve_existing_index() should explicitly pass the correct database name (from config or user input) to retrieve_vector_index_info() to ensure consistency and correctness.

System Info

System Information

OS: Darwin
OS Version: Darwin Kernel Version 24.3.0: Thu Jan 2 20:24:16 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6000
Python Version: 3.12.9 (main, Feb 4 2025, 14:38:38) [Clang 16.0.0 (clang-1600.0.26.6)]

Package Information

langchain_core: 0.3.63
langchain: 0.3.25
langchain_community: 0.3.24
langsmith: 0.2.10
langchain_neo4j: 0.4.0
langchain_openai: 0.2.14
langchain_text_splitters: 0.3.8
langgraph_sdk: 0.1.74

Optional packages not installed

langserve

Other Dependencies

aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
httpx: 0.28.1
httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
httpx>=0.25.2: Installed. No version info available.
jsonpatch<2.0,>=1.33: Installed. No version info available.
langchain-anthropic;: Installed. No version info available.
langchain-aws;: Installed. No version info available.
langchain-azure-ai;: Installed. No version info available.
langchain-cohere;: Installed. No version info available.
langchain-community;: Installed. No version info available.
langchain-core<1.0.0,>=0.3.51: Installed. No version info available.
langchain-core<1.0.0,>=0.3.58: Installed. No version info available.
langchain-core<1.0.0,>=0.3.59: Installed. No version info available.
langchain-deepseek;: Installed. No version info available.
langchain-fireworks;: Installed. No version info available.
langchain-google-genai;: Installed. No version info available.
langchain-google-vertexai;: Installed. No version info available.
langchain-groq;: Installed. No version info available.
langchain-huggingface;: Installed. No version info available.
langchain-mistralai;: Installed. No version info available.
langchain-ollama;: Installed. No version info available.
langchain-openai;: Installed. No version info available.
langchain-perplexity;: Installed. No version info available.
langchain-text-splitters<1.0.0,>=0.3.8: Installed. No version info available.
langchain-together;: Installed. No version info available.
langchain-xai;: Installed. No version info available.
langchain<1.0.0,>=0.3.25: Installed. No version info available.
langsmith-pyo3: Installed. No version info available.
langsmith<0.4,>=0.1.125: Installed. No version info available.
langsmith<0.4,>=0.1.126: Installed. No version info available.
langsmith<0.4,>=0.1.17: Installed. No version info available.
neo4j: 5.28.2
neo4j-graphrag: 1.9.0
numpy>=1.26.2;: Installed. No version info available.
numpy>=2.1.0;: Installed. No version info available.
openai: 1.98.0
orjson: 3.11.1
orjson>=3.10.1: Installed. No version info available.
packaging<25,>=23.2: Installed. No version info available.
pydantic: 2.11.7
pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
pydantic<3.0.0,>=2.7.4: Installed. No version info available.
pydantic>=2.7.4: Installed. No version info available.
PyYAML>=5.3: Installed. No version info available.
requests: 2.32.4
requests-toolbelt: 1.0.0
requests<3,>=2: Installed. No version info available.
SQLAlchemy<3,>=1.4: Installed. No version info available.
tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
tiktoken: 0.9.0
typing-extensions>=4.7: Installed. No version info available.
zstandard: Installed. No version info available.

[siddarthreddygsr]

I think this behavior is intentional by design and not a bug. Waiting for a maintainer to respond.