Vector Embeddings¶

Examples¶

The following examples use the vector similarity functions.

This SQL example uses the VECTOR_INNER_PRODUCT function to determine which vectors in the table are closest to each other between columns a and b:

CREATE TABLE vectors (a VECTOR(float, 3), b VECTOR(float, 3));
INSERT INTO vectors SELECT [1.1,2.2,3]::VECTOR(FLOAT,3), [1,1,1]::VECTOR(FLOAT,3);
INSERT INTO vectors SELECT [1,2.2,3]::VECTOR(FLOAT,3), [4,6,8]::VECTOR(FLOAT,3);

-- Compute the pairwise inner product between columns a and b
SELECT VECTOR_INNER_PRODUCT(a, b) FROM vectors;

+------+
| 6.3  |
|------|
| 41.2 |
+------+

This SQL example calls the VECTOR_COSINE_SIMILARITY function to find the vector closes to [1,2,3]:

SELECT a, VECTOR_COSINE_SIMILARITY(a, [1,2,3]::VECTOR(FLOAT, 3)) AS similarity
    FROM vectors
ORDER BY similarity DESC
LIMIT 1;

+-------------------------+
| [1, 2.2, 3] | 0.9990... |
+-------------------------+

import snowflake.connector

conn = ... # Set up connection
cur = conn.cursor()

# Create a table and insert some vectors
cur.execute("CREATE OR REPLACE TABLE vectors (a VECTOR(FLOAT, 3), b VECTOR(FLOAT, 3))")
values = [([1.1, 2.2, 3], [1, 1, 1]), ([1, 2.2, 3], [4, 6, 8])]
for row in values:
        cur.execute(f"""
            INSERT INTO vectors(a, b)
                SELECT {row[0]}::VECTOR(FLOAT,3), {row[1]}::VECTOR(FLOAT,3)
        """)

# Compute the pairwise inner product between columns a and b
cur.execute("SELECT VECTOR_INNER_PRODUCT(a, b) FROM vectors")
print(cur.fetchall())

[(6.30...,), (41.2...,)]

# Find the closest vector to [1,2,3]
cur.execute(f"""
    SELECT a, VECTOR_COSINE_SIMILARITY(a, {[1,2,3]}::VECTOR(FLOAT, 3))
        AS similarity
        FROM vectors
        ORDER BY similarity DESC
        LIMIT 1;
""")
print(cur.fetchall())

[([1.0, 2.2..., 3.0], 0.9990...)]

from snowflake.snowpark import Session, Row
session = ... # Set up session
from snowflake.snowpark.types import VectorType, StructType, StructField
from snowflake.snowpark.functions import col, lit, vector_l2_distance
schema = StructType([StructField("vec", VectorType(int, 3))])
data = [Row([1, 2, 3]), Row([4, 5, 6]), Row([7, 8, 9])]
df = session.create_dataframe(data, schema)
df.select(
    "vec",
    vector_l2_distance(df.vec, lit([1, 2, 2]).cast(VectorType(int, 3))).as_("dist"),
).sort("dist").limit(1).show()

----------------------
|"VEC"      |"DIST"  |
----------------------
|[1, 2, 3]  |1.0     |
----------------------

Vector similarity search¶

To implement a search for semantically similar documents, first store the embeddings for the documents to be searched. Keep the embeddings up to date when documents are added or edited.

In this example, the documents are call center issues logged by support representatives. The issue is stored in a column called issue_text in the table issues. The following SQL creates a new vector column to hold the embeddings of the issues.

ALTER TABLE issues ADD COLUMN issue_vec VECTOR(FLOAT, 768);

UPDATE issues
  SET issue_vec = SNOWFLAKE.CORTEX.EMBED_TEXT_768('snowflake-arctic-embed-m', issue_text);

To perform a search, create an embedding of the search term or target document, then use a vector similarity function to locate documents with similar embeddings. Use ORDER BY and LIMIT clauses to select the top k matching documents, and optionally use a WHERE condition to specify a minimum similarity.

Generally, the call to the vector similarity function should appear in the SELECT clause, not in the WHERE clause. This way, the function is called only for the rows specified by the WHERE clause, which may restrict the query based on some other criteria, instead of operating over all rows in the table. To test a similarity value in the WHERE clause, define a column alias for the VECTOR_COSINE_SIMILARITY call in the SELECT clause, and use that alias in a condition in the WHERE clause.

This example finds up to five issues matching the search term from the last 90 days, assuming the cosine similarity with the search term is at least 0.7.

SELECT
  issue,
  VECTOR_COSINE_SIMILARITY(
    issue_vec,
    SNOWFLAKE.CORTEX.EMBED_TEXT_768('snowflake-arctic-embed-m', 'User could not install Facebook app on his phone')
  ) AS similarity
FROM issues
ORDER BY similarity DESC
LIMIT 5
WHERE DATEDIFF(day, CURRENT_DATE(), issue_date) < 90 AND similarity > 0.7;

Retrieval-Augmented Generation (RAG)¶

In retrieval-augmented generation (RAG), a user’s query is used to find similar documents using vector similarity. The top document is then passed to a large language model (LLM) along with the user’s query, providing context for the generative response (completion). This can improve the appropriateness of the response significantly.

In the following example, wiki is a table with a text column content, and query is a single-row table with a text column text.

-- Create embedding vectors for wiki articles (only do once)
ALTER TABLE wiki ADD COLUMN vec VECTOR(FLOAT, 768);
UPDATE wiki SET vec = SNOWFLAKE.CORTEX.EMBED_TEXT_768('snowflake-arctic-embed-m', content);

-- Embed incoming query
SET query = 'in which year was Snowflake Computing founded?';
CREATE OR REPLACE TABLE query_table (query_vec VECTOR(FLOAT, 768));
INSERT INTO query_table SELECT SNOWFLAKE.CORTEX.EMBED_TEXT_768('snowflake-arctic-embed-m', $query);

-- Do a semantic search to find the relevant wiki for the query
WITH result AS (
    SELECT
        w.content,
        $query AS query_text,
        VECTOR_COSINE_SIMILARITY(w.vec, q.query_vec) AS similarity
    FROM wiki w, query_table q
    ORDER BY similarity DESC
    LIMIT 1
)

-- Pass to large language model as context
SELECT SNOWFLAKE.CORTEX.COMPLETE('mistral-7b',
    CONCAT('Answer this question: ', query_text, ' using this text: ', content)) FROM result;