Added Cohere example [skip ci]

Author: ankane

README.md

@@ -36,6 +36,7 @@ And follow the instructions for your database library:
 Or check out an example:
 
 - [Embeddings](src/test/java/com/pgvector/OpenAITest.java) with OpenAI
+- [Binary embeddings](src/test/java/com/pgvector/CohereTest.java) with Cohere
 
 ## JDBC (Java)
 

src/test/java/com/pgvector/CohereTest.java

@@ -0,0 +1,101 @@
+package com.pgvector;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpRequest.BodyPublishers;
+import java.net.http.HttpResponse;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.ArrayList;
+import java.util.List;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import com.pgvector.PGvector;
+import org.postgresql.PGConnection;
+import org.junit.jupiter.api.Test;
+
+public class CohereTest {
+    @Test
+    void example() throws IOException, InterruptedException, SQLException {
+        String apiKey = System.getenv("CO_API_KEY");
+        if (apiKey == null) {
+            return;
+        }
+
+        Connection conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/pgvector_example");
+
+        Statement setupStmt = conn.createStatement();
+        setupStmt.executeUpdate("CREATE EXTENSION IF NOT EXISTS vector");
+        setupStmt.executeUpdate("DROP TABLE IF EXISTS documents");
+
+        PGvector.addVectorType(conn);
+
+        Statement createStmt = conn.createStatement();
+        createStmt.executeUpdate("CREATE TABLE documents (id bigserial PRIMARY KEY, content text, embedding bit(1024))");
+
+        String[] input = {
+            "The dog is barking",
+            "The cat is purring",
+            "The bear is growling"
+        };
+        List<byte[]> embeddings = fetchEmbeddings(input, "search_document", apiKey);
+        for (int i = 0; i < input.length; i++) {
+            PreparedStatement insertStmt = conn.prepareStatement("INSERT INTO documents (content, embedding) VALUES (?, ?)");
+            insertStmt.setString(1, input[i]);
+            insertStmt.setObject(2, new PGbit(embeddings.get(i)));
+            insertStmt.executeUpdate();
+        }
+
+        String query = "forest";
+        byte[] queryEmbedding = fetchEmbeddings(new String[] {query}, "search_query", apiKey).get(0);
+        PreparedStatement neighborStmt = conn.prepareStatement("SELECT * FROM documents ORDER BY embedding <~> ? LIMIT 5");
+        neighborStmt.setObject(1, new PGbit(queryEmbedding));
+        ResultSet rs = neighborStmt.executeQuery();
+        while (rs.next()) {
+            System.out.println(rs.getString("content"));
+        }
+
+        conn.close();
+    }
+
+    // https://docs.cohere.com/reference/embed
+    private List<byte[]> fetchEmbeddings(String[] texts, String inputType, String apiKey) throws IOException, InterruptedException {
+        ObjectMapper mapper = new ObjectMapper();
+        ObjectNode root = mapper.createObjectNode();
+        for (String v : texts) {
+            root.withArray("texts").add(v);
+        }
+        root.put("model", "embed-english-v3.0");
+        root.put("input_type", inputType);
+        root.withArray("embedding_types").add("ubinary");
+        String json = mapper.writeValueAsString(root);
+
+        HttpClient client = HttpClient.newHttpClient();
+        HttpRequest request = HttpRequest.newBuilder()
+            .uri(URI.create("https://api.cohere.com/v1/embed"))
+            .header("Authorization", "Bearer " + apiKey)
+            .header("Content-Type", "application/json")
+            .POST(BodyPublishers.ofString(json))
+            .build();
+        HttpResponse<String> response = client.send(request, BodyHandlers.ofString());
+
+        List<byte[]> embeddings = new ArrayList<>();
+        for (JsonNode n : mapper.readTree(response.body()).get("embeddings").get("ubinary")) {
+            byte[] embedding = new byte[n.size()];
+            int i = 0;
+            for (JsonNode v : n) {
+                embedding[i++] = (byte) v.asDouble();
+            }
+            embeddings.add(embedding);
+        }
+        return embeddings;
+    }
+}