community: update Memgraph integration

[katarinasupe]

Description:

• Memgraph no longer relies on Neo4jGraphStore but implements GraphStore, just like other graph databases.
• Memgraph no longer relies on GraphQAChain, but implements MemgraphQAChain, just like other graph databases.
• The refresh schema procedure has been updated to try using SHOW SCHEMA INFO. The fallback uses Cypher queries (a combination of schema and Cypher) → LangChain integration no longer relies on MAGE library.
• The schema structure has been reformatted. Regardless of the procedures used to get schema, schema structure is the same.
• The add_graph_documents() method has been implemented. It transforms GraphDocument into Cypher queries and creates a graph in Memgraph. It implements the ability to use baseEntityLabel to improve speed (baseEntityLabel has an index on the id property). It also implements the ability to include sources by creating a MENTIONS relationship to the source document.
• Jupyter Notebook for Memgraph has been updated.
• Issue: /
• Dependencies: /
• Twitter handle: supe_katarina (DX Engineer @ Memgraph)

Closes #25606

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Name	Status	Preview	Comments	Updated (UTC)
langchain	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 29, 2024 1:19pm

[katarinasupe]

Hi @baskaryan, tagging as noted in PR template. Please let me know what I need to do regarding the test and what's needed to do in order to get this merged.

[katarinasupe]

I managed to fix the CI. Now, all is passing.

Tagging @efriis, as the other person from the PR template for the review. Let me know if someone else should be tagged.

[efriis]

Hey! Here's a link to the review policy: https://python.langchain.com/docs/contributing/review_process/

Status is currently needs support

[katarinasupe]

@efriis is there any update? I have more than 5 upvotes so I am wondering what's the next course of action here and if I can help somehow.

[katarinasupe]

Thank you, @libraua, for approving this PR. Is there something else I need to do to get this PR merged? I wanted to enable Memgraph developers to utilize Memgraph LangChain integration with the latest improvements.

[ccurme]

Hi @katarinasupe, I don't want to block this but have some qualms about MemgraphQAChain. I think the fact that other graph databases implement custom Chain classes is not an advantage and may not be desirable to emulate. MemgraphQAChain also uses LLMChain, which is deprecated (I include a comment below).

LangChain is investing in LangGraph, and instead of releasing and maintaining a v0.0 abstraction, you could advantage yourself by implementing these as tools and adding documentation demonstrating their use in question-answering using a modern agent framework.

• Migration guides for other chains: https://python.langchain.com/docs/versions/migrating_chains/
• Example of how we'd recommend querying SQL data using an agent: https://python.langchain.com/docs/integrations/tools/sql_database/#use-within-an-agent

Our documentation across integrations has not kept up with our current understanding of best practices, so apologies for the confusion. If you want to move forward with MemgraphQAChain we can go ahead (but suggest we remove LLMChain). Wanted to make sure you're aware of current best practices first.

[ccurme]

do we need use_cypher_llm_kwargs or use_qa_llm_kwargs? Ideally we would avoid LLMChain and just use prompt | llm | parser (e.g., as you do above).

[katarinasupe]

Thank you for the review. Let me digest this today and figure out the next best steps 🙏

[katarinasupe]

Hi @ccurme, based on your suggestion, I removed LLMChain. Please let me know if I did that correctly. I changed the code, so it's working for the example provided in the Jupyter Notebook. Let me know if I missed smth while updating chains from LLMChain to Runnable types.

Although it's not ideal, I would like this PR to be merged. I see devs using it, and I would like this work not to go to waste. Still, I am interested in following the best practices out there. I need to take a deeper look at the tools you sent me. If I understood correctly, no other graph database currently follows this approach, or?

[katarinasupe]

Hi @ccurme any updates here? I would love to get this merged if possible 🙏

[pthalasta]

@ccurme is this available as part of langchain-core==0.3.23?

[ccurme]

This will be available in the next release of langchain-community (0.3.11)