First commit

.github/workflows/build.yml

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+name: build
+on: [push, pull_request]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ankane/setup-postgres@v1
+        with:
+          database: pgvector_c_test
+      - run: |
+          cd /tmp
+          git clone --branch v0.5.1 https://github.com/pgvector/pgvector.git
+          cd pgvector
+          make
+          sudo make install
+      - run: gcc -Wall -Wextra -Werror -o test/pq test/pq_test.cpp -lpq
+      - run: test/pq

.gitignore

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+/test/pq

LICENSE.txt

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+The MIT License (MIT)
+
+Copyright (c) 2023 Andrew Kane
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# pgvector-c
+
+[pgvector](https://github.com/pgvector/pgvector) examples for C
+
+Supports [libpq](https://www.postgresql.org/docs/current/libpq.html)
+
+[![Build Status](https://github.com/pgvector/pgvector-c/workflows/build/badge.svg?branch=master)](https://github.com/pgvector/pgvector-c/actions)
+
+## Getting Started
+
+Follow the instructions for your database library:
+
+- [libpq](#libpq)
+
+## libpq
+
+Enable the extension
+
+```c
+PGresult *res = PQexec(conn, "CREATE EXTENSION IF NOT EXISTS vector");
+```
+
+Create a table
+
+```c
+PGresult *res = PQexec(conn, "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3))");
+```
+
+Insert vectors
+
+```c
+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
+
+```c
+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);
+```
+
+See a [full example](test/pq_test.c)
+
+## Contributing
+
+Everyone is encouraged to help improve this project. Here are a few ways you can help:
+
+- [Report bugs](https://github.com/pgvector/pgvector-c/issues)
+- Fix bugs and [submit pull requests](https://github.com/pgvector/pgvector-c/pulls)
+- Write, clarify, or fix documentation
+- Suggest or add new features
+
+To get started with development:
+
+```sh
+git clone https://github.com/pgvector/pgvector-c.git
+cd pgvector-c
+createdb pgvector_c_test
+gcc -Wall -Wextra -Werror -o test/pq test/pq_test.c -lpq
+test/pq
+```

test/pq_test.c

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+#include <assert.h>
+#include <libpq-fe.h>
+
+int main() {
+    PGconn *conn;
+    PGresult *res;
+
+    conn = PQconnectdb("postgres://localhost/pgvector_c_test");
+    assert(PQstatus(conn) == CONNECTION_OK);
+
+    res = PQexec(conn, "CREATE EXTENSION IF NOT EXISTS vector");
+    assert(PQresultStatus(res) == PGRES_COMMAND_OK);
+    PQclear(res);
+
+    res = PQexec(conn, "DROP TABLE IF EXISTS items");
+    assert(PQresultStatus(res) == PGRES_COMMAND_OK);
+    PQclear(res);
+
+    res = PQexec(conn, "CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3))");
+    assert(PQresultStatus(res) == PGRES_COMMAND_OK);
+    PQclear(res);
+
+    const char *paramValues[3] = {"[1,1,1]", "[2,2,2]", "[1,1,2]"};
+    res = PQexecParams(conn, "INSERT INTO items (embedding) VALUES ($1), ($2), ($3)", 3, NULL, paramValues, NULL, NULL, 0);
+    assert(PQresultStatus(res) == PGRES_COMMAND_OK);
+    PQclear(res);
+
+    const char *paramValues2[1] = {"[1,1,1]"};
+    res = PQexecParams(conn, "SELECT * FROM items ORDER BY embedding <-> $1 LIMIT 5", 1, NULL, paramValues2, NULL, NULL, 0);
+    assert(PQresultStatus(res) == PGRES_TUPLES_OK);
+    int ntuples = PQntuples(res);
+    for (int i = 0; i < ntuples; i++) {
+        printf("%s: %s\n", PQgetvalue(res, i, 0), PQgetvalue(res, i, 1));
+    }
+    PQclear(res);
+
+    PQfinish(conn);
+
+    return 0;
+}