Vector Similarity

Vectors (also called “Embeddings”), represent an AI model’s impression (or understanding) of a piece of unstructured data like text, images, audio, videos, etc. Vector Similarity Search (VSS) is the process of finding vectors in the vector database that are similar to a given query vector. Popular VSS uses include recommendation systems, image and video search, document retrieval, and question answering.

Index Creation

Before doing vector search, first define the schema and create an index.

import redis
from redis.commands.search.field import TagField, VectorField
from redis.commands.search.indexDefinition import IndexDefinition, IndexType
from redis.commands.search.query import Query

r = redis.Redis(host="localhost", port=6379)

INDEX_NAME = "index"                              # Vector Index Name
DOC_PREFIX = "doc:"                               # RediSearch Key Prefix for the Index

def create_index(vector_dimensions: int):
    try:
        # check to see if index exists
        r.ft(INDEX_NAME).info()
        print("Index already exists!")
    except:
        # schema
        schema = (
            TagField("tag"),                       # Tag Field Name
            VectorField("vector",                  # Vector Field Name
                "FLAT", {                          # Vector Index Type: FLAT or HNSW
                    "TYPE": "FLOAT32",             # FLOAT32 or FLOAT64
                    "DIM": vector_dimensions,      # Number of Vector Dimensions
                    "DISTANCE_METRIC": "COSINE",   # Vector Search Distance Metric
                }
            ),
        )

        # index Definition
        definition = IndexDefinition(prefix=[DOC_PREFIX], index_type=IndexType.HASH)

        # create Index
        r.ft(INDEX_NAME).create_index(fields=schema, definition=definition)

We’ll start by working with vectors that have 1536 dimensions.

# define vector dimensions
VECTOR_DIMENSIONS = 1536

# create the index
create_index(vector_dimensions=VECTOR_DIMENSIONS)

Adding Vectors to Redis

Next, we add vectors (dummy data) to Redis using hset. The search index listens to keyspace notifications and will include any written HASH objects prefixed by DOC_PREFIX.

%pip install numpy

import numpy as np

# instantiate a redis pipeline
pipe = r.pipeline()

# define some dummy data
objects = [
    {"name": "a", "tag": "foo"},
    {"name": "b", "tag": "foo"},
    {"name": "c", "tag": "bar"},
]

# write data
for obj in objects:
    # define key
    key = f"doc:{obj['name']}"
    # create a random "dummy" vector
    obj["vector"] = np.random.rand(VECTOR_DIMENSIONS).astype(np.float32).tobytes()
    # HSET
    pipe.hset(key, mapping=obj)

res = pipe.execute()

Searching

You can use VSS queries with the .ft(...).search(...) query command. To use a VSS query, you must specify the option .dialect(2).

There are two supported types of vector queries in Redis: KNN and Range. Hybrid queries can work in both settings and combine elements of traditional search and VSS.

KNN Queries

KNN queries are for finding the topK most similar vectors given a query vector.

query = (
    Query("*=>[KNN 2 @vector $vec as score]")
     .sort_by("score")
     .return_fields("id", "score")
     .paging(0, 2)
     .dialect(2)
)

query_params = {
    "vec": np.random.rand(VECTOR_DIMENSIONS).astype(np.float32).tobytes()
}
r.ft(INDEX_NAME).search(query, query_params).docs

[Document {'id': 'doc:b', 'payload': None, 'score': '0.2376562953'},
 Document {'id': 'doc:c', 'payload': None, 'score': '0.240063905716'}]

Range Queries

Range queries provide a way to filter results by the distance between a vector field in Redis and a query vector based on some pre-defined threshold (radius).

query = (
    Query("@vector:[VECTOR_RANGE $radius $vec]=>{$YIELD_DISTANCE_AS: score}")
     .sort_by("score")
     .return_fields("id", "score")
     .paging(0, 3)
     .dialect(2)
)

# Find all vectors within 0.8 of the query vector
query_params = {
    "radius": 0.8,
    "vec": np.random.rand(VECTOR_DIMENSIONS).astype(np.float32).tobytes()
}
r.ft(INDEX_NAME).search(query, query_params).docs

[Document {'id': 'doc:a', 'payload': None, 'score': '0.243115246296'},
 Document {'id': 'doc:c', 'payload': None, 'score': '0.24981123209'},
 Document {'id': 'doc:b', 'payload': None, 'score': '0.251443207264'}]

See additional Range Query examples in this Jupyter notebook.

Hybrid Queries

Hybrid queries contain both traditional filters (numeric, tags, text) and VSS in one single Redis command.

query = (
    Query("(@tag:{ foo })=>[KNN 2 @vector $vec as score]")
     .sort_by("score")
     .return_fields("id", "tag", "score")
     .paging(0, 2)
     .dialect(2)
)

query_params = {
    "vec": np.random.rand(VECTOR_DIMENSIONS).astype(np.float32).tobytes()
}
r.ft(INDEX_NAME).search(query, query_params).docs

[Document {'id': 'doc:b', 'payload': None, 'score': '0.24422544241', 'tag': 'foo'},
 Document {'id': 'doc:a', 'payload': None, 'score': '0.259926855564', 'tag': 'foo'}]

See additional Hybrid Query examples in this Jupyter notebook.

Vector Creation and Storage Examples

The above examples use dummy data as vectors. However, in reality, most use cases leverage production-grade AI models for creating embeddings. Below we will take some sample text data, pass it to the OpenAI and Cohere API’s respectively, and then write them to Redis.

texts = [
    "Today is a really great day!",
    "The dog next door barks really loudly.",
    "My cat escaped and got out before I could close the door.",
    "It's supposed to rain and thunder tomorrow."
]

OpenAI Embeddings

Before working with OpenAI Embeddings, we clean up our existing search index and create a new one.

# delete index
r.ft(INDEX_NAME).dropindex(delete_documents=True)

# make a new one
create_index(vector_dimensions=VECTOR_DIMENSIONS)

%pip install openai

import openai

# set your OpenAI API key - get one at https://platform.openai.com
openai.api_key = "YOUR OPENAI API KEY"

# Create Embeddings with OpenAI text-embedding-ada-002
# https://openai.com/blog/new-and-improved-embedding-model
response = openai.Embedding.create(input=texts, engine="text-embedding-ada-002")
embeddings = np.array([r["embedding"] for r in response["data"]], dtype=np.float32)

# Write to Redis
pipe = r.pipeline()
for i, embedding in enumerate(embeddings):
    pipe.hset(f"doc:{i}", mapping = {
        "vector": embedding.tobytes(),
        "content": texts[i],
        "tag": "openai"
    })
res = pipe.execute()

embeddings

array([[ 0.00509819,  0.0010873 , -0.00228475, ..., -0.00457579,
         0.01329307, -0.03167175],
       [-0.00357223, -0.00550784, -0.01314328, ..., -0.02915693,
         0.01470436, -0.01367203],
       [-0.01284631,  0.0034875 , -0.01719686, ..., -0.01537451,
         0.01953256, -0.05048691],
       [-0.01145045, -0.00785481,  0.00206323, ..., -0.02070181,
        -0.01629098, -0.00300795]], dtype=float32)

Search with OpenAI Embeddings

Now that we’ve created embeddings with OpenAI, we can also perform a search to find relevant documents to some input text.

text = "animals"

# create query embedding
response = openai.Embedding.create(input=[text], engine="text-embedding-ada-002")
query_embedding = np.array([r["embedding"] for r in response["data"]], dtype=np.float32)[0]

query_embedding

array([ 0.00062901, -0.0070723 , -0.00148926, ..., -0.01904645,
       -0.00436092, -0.01117944], dtype=float32)

# query for similar documents that have the openai tag
query = (
    Query("(@tag:{ openai })=>[KNN 2 @vector $vec as score]")
     .sort_by("score")
     .return_fields("content", "tag", "score")
     .paging(0, 2)
     .dialect(2)
)

query_params = {"vec": query_embedding.tobytes()}
r.ft(INDEX_NAME).search(query, query_params).docs

# the two pieces of content related to animals are returned

[Document {'id': 'doc:1', 'payload': None, 'score': '0.214349985123', 'content': 'The dog next door barks really loudly.', 'tag': 'openai'},
 Document {'id': 'doc:2', 'payload': None, 'score': '0.237052619457', 'content': 'My cat escaped and got out before I could close the door.', 'tag': 'openai'}]

Cohere Embeddings

Before working with Cohere Embeddings, we clean up our existing search index and create a new one.

# delete index
r.ft(INDEX_NAME).dropindex(delete_documents=True)

# make a new one for cohere embeddings (1024 dimensions)
VECTOR_DIMENSIONS = 1024
create_index(vector_dimensions=VECTOR_DIMENSIONS)

%pip install cohere

import cohere

co = cohere.Client("YOUR COHERE API KEY")

# Create Embeddings with Cohere
# https://docs.cohere.ai/docs/embeddings
response = co.embed(texts=texts, model="small")
embeddings = np.array(response.embeddings, dtype=np.float32)

# Write to Redis
for i, embedding in enumerate(embeddings):
    r.hset(f"doc:{i}", mapping = {
        "vector": embedding.tobytes(),
        "content": texts[i],
        "tag": "cohere"
    })

embeddings

array([[-0.3034668 , -0.71533203, -0.2836914 , ...,  0.81152344,
         1.0253906 , -0.8095703 ],
       [-0.02560425, -1.4912109 ,  0.24267578, ..., -0.89746094,
         0.15625   , -3.203125  ],
       [ 0.10125732,  0.7246094 , -0.29516602, ..., -1.9638672 ,
         1.6630859 , -0.23291016],
       [-2.09375   ,  0.8588867 , -0.23352051, ..., -0.01541138,
         0.17053223, -3.4042969 ]], dtype=float32)

Search with Cohere Embeddings

Now that we’ve created embeddings with Cohere, we can also perform a search to find relevant documents to some input text.

text = "animals"

# create query embedding
response = co.embed(texts=[text], model="small")
query_embedding = np.array(response.embeddings[0], dtype=np.float32)

query_embedding

array([-0.49682617,  1.7070312 ,  0.3466797 , ...,  0.58984375,
        0.1060791 , -2.9023438 ], dtype=float32)

# query for similar documents that have the cohere tag
query = (
    Query("(@tag:{ cohere })=>[KNN 2 @vector $vec as score]")
     .sort_by("score")
     .return_fields("content", "tag", "score")
     .paging(0, 2)
     .dialect(2)
)

query_params = {"vec": query_embedding.tobytes()}
r.ft(INDEX_NAME).search(query, query_params).docs

# the two pieces of content related to animals are returned

[Document {'id': 'doc:1', 'payload': None, 'score': '0.658673524857', 'content': 'The dog next door barks really loudly.', 'tag': 'cohere'},
 Document {'id': 'doc:2', 'payload': None, 'score': '0.662699103355', 'content': 'My cat escaped and got out before I could close the door.', 'tag': 'cohere'}]

Find more example apps, tutorials, and projects using Redis Vector Similarity Search in this GitHub organization.