Selecting an Embedding Model

The easiest option here is to select amongst Huggingface’s SentenceTransformers library, this allows you to pop it into your python code via:

from sentence_transformers import SentenceTransformer

model = SentenceTransformer('sentence-transformers/all-minilm-l6-v2')

Select an embedding model amongst the list here:

Creating a MongoDB Vector Index

Depending on the embedding model you selected, you’ll need to define the index definition. So if the model is 768 dimensions, you’ll specifigy it like:

  "mappings": {
    "dynamic": true,
    "fields": {
      "plot_embedding_768": {
        "dimensions": 768,
        "similarity": "euclidean",
        "type": "knnVector"

plot_embedding_768 in this case is any field that contains the 768 dimension array.

Consult the MongoDB Vector search docs to understand the various similarity options of euclidian, dotproduct and cosine.

Indexing Data

Using the SentenceTransformer imported above, iterate through whichever dataset you want, encode each and simply insert.

Make sure the field you’re inserting the encoded array into is the same dimension count
from pymongo import MongoClient
from sentence_transformers import SentenceTransformer
import asyncio
from dotenv import load_dotenv
import os


# Initialize the SentenceTransformer
model = SentenceTransformer('sentence-transformers/all-minilm-l6-v2')

# Grab connection string from env variabl
connection_string = os.getenv('mdb')

# Connect to MongoDB and use default loaded data
client = MongoClient(connection_string)
db = client['sample_mflix']
collection = db['embedded_movies']

async def encode(self, text):
    loop = asyncio.get_event_loop()
    embedding = await loop.run_in_executor(None, model.encode, [text])
    return embedding[0].tolist()

# Get all documents
documents = collection.find()

# Update each document
for doc in documents:
    if 'plot' not in doc:
    embedding = model.encode([doc['plot']])[0].tolist()
        {'_id': doc['_id']},
        {'$set': {'plot_embedding_768': embedding}}

Building your Workbook

  1. First add the MongoDB block:
  1. Then specify the embedding model you’ll use

Provide your connection string (end to end encrypted, consult our security page to learn more), database and collection.

  1. Now write the query.

Note, we’re including the {{paarameters.query}} variable here, and wrapping it in quotes. Consult the Block Intros Page to understand variable syntax.

    '$vectorSearch': {
      'index': 'default',
      'path': 'plot_embedding_384',
      'queryVector': "{{parameters.query}}",
      'numCandidates': 150,
      'limit': 10
      'plot': 1, 'title' : 1
  1. Read em and weep the results, note the runtime :)
    "block_id": "08d33a0c",
    "cell_name": "index_string",
    "response": [
            "plot": "A true story about four Allied POWs who endure harsh treatment from their Japanese captors during World War II while being forced to build a railroad through the Burmese jungle. Ultimately ...",
            "title": "To End All Wars"
            "plot": "The intertwined stories of three Marines during America's battle with the Japanese in the Pacific during World War II.",
            "title": "The Pacific"
            "plot": "A \"Hitlerjugend\" kind of story, set in the Soviet Union during the Second World War, based on a fictitious story from the eponymous book by Vladimir Kunin. The Red Army has a gang of ...",
            "title": "Bastards"
            "plot": "A young Korean man arrives in Japan near the end of World War II with hopes of being a fighter pilot, but ends up on the streets battling racism, organized crime, occupying American ...",
            "title": "Fighter in the Wind"
            "plot": "The story of ordinary men during WWII as seen from three different points of View.",
            "title": "The Fallen"
            "plot": "A fantastic tale of war, love, family and ambition set in the midst of the Japanese Civil Wars of the sixteenth century.",
            "title": "Ugetsu"
            "plot": "A dramatization of the World War II Battle of Iwo Jima.",
            "title": "Sands of Iwo Jima"
            "plot": "The story of student-soldiers trying to protect a middle school during the early days of the Korean War.",
            "title": "71: Into the Fire"
            "plot": "Several yakuza from Tokyo are sent to Okinawa to help end a gang war. The war escalates and the Tokyo drifters decide to lay low at the beach.",
            "title": "Sonatine"
            "plot": "In World War II-era Korea, rival runners, one Korean (Jang Dong-gun) and one Japanese (Joe Odagiri), go to war together against the Soviets.",
            "title": "My Way"
    "metadata": {
        "block_type": "data",
        "block_subtype": "mongodb",
        "runtime": 757.905517578125
    "error": null,
    "status": 200,
    "run_at": "2024-02-14T15:35:28.144000"

Integrating it into your App