# MangoDB error in RAG tutorial

**URL:** <https://forum.langchain.com/t/mangodb-error-in-rag-tutorial/2454>\
**Category:** LangChain\
**Tags:** python-help\
**Created:** [December 9, 2025, 5:58am UTC](https://forum.langchain.com/t/mangodb-error-in-rag-tutorial/2454 "2025-12-09T05:58:01Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![JayKayNJIT](https://yyz1.discourse-cdn.com/flex007/user_avatar/forum.langchain.com/jaykaynjit/32/1882_2.png) [@JayKayNJIT](https://forum.langchain.com/u/JayKayNJIT)\
**Post date:** [December 9, 2025, 5:58am UTC](https://forum.langchain.com/t/mangodb-error-in-rag-tutorial/2454/1 "2025-12-09T05:58:01Z")

</div>

I am trying to reproduce RAG tutorial ([https://docs.langchain.com/oss/javascript/langchain/get-help](https://docs.langchain.com/oss/javascript/langchain/get-help)) in Colab but it is throwing following error.

 ![image](https://canada1.discourse-cdn.com/flex007/uploads/langchain/original/2X/c/ccd85909179d9ff139d3eec27a00dc7de27be43b.png)

---

<div class="post-metadata">

**Author:** ![keenborder786](https://yyz1.discourse-cdn.com/flex007/user_avatar/forum.langchain.com/keenborder786/32/1757_2.png) [@keenborder786](https://forum.langchain.com/u/keenborder786)\
**Post date:** [March 9, 2026, 11:20am UTC](https://forum.langchain.com/t/mangodb-error-in-rag-tutorial/2454/2 "2026-03-09T11:20:01Z")

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@JayKayNJIT You need to define the variable `MONGODB_COLLECTION` first.

```python
from pymongo import MongoClient
from langchain_mongodb import MongoDBAtlasVectorSearch

MongoDB connection

MONGODB_URI = “your_mongodb_connection_string”
client = MongoClient(MONGODB_URI)

Database and collection

db = client[“your_database_name”]
collection = db[“your_collection_name”]

Vector index name created in MongoDB Atlas

ATLAS_VECTOR_SEARCH_INDEX_NAME = “vector_index”

Create vector store

vector_store = MongoDBAtlasVectorSearch(
embedding=embeddings,
collection=collection,
index_name=ATLAS_VECTOR_SEARCH_INDEX_NAME,
relevance_score_fn=“cosine”,
)

```