pgvector-c

pgvector examples for C

Supports libpq

Getting Started

Follow the instructions for your database library:

• libpq

Or check out some examples:

• Embeddings with OpenAI
• Binary embeddings with Cohere
• Bulk loading with COPY

libpq

Enable the extension

PGresult *res = PQexec(conn, "CREATE EXTENSION IF NOT EXISTS vector");

Create a table

PGresult *res = PQexec(conn, "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3))");

Insert vectors

const char *paramValues[2] = {"[1,2,3]", "[4,5,6]"};
PGresult *res = PQexecParams(conn, "INSERT INTO items (embedding) VALUES ($1), ($2)", 2, NULL, paramValues, NULL, NULL, 0);

Get the nearest neighbors

const char *paramValues[1] = {"[3,1,2]"};
PGresult *res = PQexecParams(conn, "SELECT * FROM items ORDER BY embedding <-> $1 LIMIT 5", 1, NULL, paramValues, NULL, NULL, 0);

Add an approximate index

PGresult *res = PQexec(conn, "CREATE INDEX ON items USING hnsw (embedding vector_l2_ops)");
// or
PGresult *res = PQexec(conn, "CREATE INDEX ON items USING ivfflat (embedding vector_l2_ops) WITH (lists = 100)");

Use vector_ip_ops for inner product and vector_cosine_ops for cosine distance

See a full example

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features

To get started with development:

git clone https://github.com/pgvector/pgvector-c.git
cd pgvector-c
createdb pgvector_c_test
cmake -S . -B build
cmake --build build
build/test

To run an example:

cd examples/openai
createdb pgvector_example
cmake -S . -B build
cmake --build build
build/example