Fix for UNKNOWN DATABASE exception

sink-connector/src/main/java/com/altinity/clickhouse/sink/connector/db/operations/ClickHouseCreateDatabase.java

@@ -6,6 +6,7 @@
 
 public class ClickHouseCreateDatabase extends ClickHouseTableOperationsBase {
     public void createNewDatabase(ClickHouseConnection conn, String dbName) throws SQLException {
-        this.runQuery(String.format("CREATE DATABASE %s", dbName), conn);
+        String query = String.format("USE system; CREATE DATABASE IF NOT EXISTS %s; USE %s", dbName, dbName);
+        this.runQuery(query, conn);
     }
 }

sink-connector/src/test/java/com/altinity/clickhouse/sink/connector/db/operations/ClickHouseCreateDatabaseTest.java

@@ -0,0 +1,69 @@
+package com.altinity.clickhouse.sink.connector.db.operations;
+
+import com.altinity.clickhouse.sink.connector.ClickHouseSinkConnectorConfig;
+import com.clickhouse.jdbc.ClickHouseConnection;
+import com.altinity.clickhouse.sink.connector.db.DbWriter;
+import com.altinity.clickhouse.sink.connector.db.operations.ClickHouseCreateDatabase;
+
+import org.junit.Assert;
+import org.testcontainers.junit.jupiter.Testcontainers;
+import org.testcontainers.junit.jupiter.Container;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.testcontainers.clickhouse.ClickHouseContainer;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Properties;
+import java.util.ArrayList;
+import java.util.HashMap;
+
+@Testcontainers
+
+public class ClickHouseCreateDatabaseTest {
+
+    static DbWriter dbWriter;
+    static DbWriter maintenanceDbWriter;
+    static String dbName;
+
+    @Container
+    private static ClickHouseContainer clickHouseContainer = new ClickHouseContainer("clickhouse/clickhouse-server:latest");
+    @BeforeAll
+    static void initialize() {
+
+        String hostName = clickHouseContainer.getHost();
+        Integer port = clickHouseContainer.getMappedPort(8123);
+        String userName = "default";
+        String password = "";
+        String systemDb = "system";
+        dbName = "test_create_db";
+
+        ClickHouseSinkConnectorConfig config= new ClickHouseSinkConnectorConfig(new HashMap<>());
+        dbWriter = new DbWriter(hostName, port, dbName, null, userName, password, config, null);
+        maintenanceDbWriter = new DbWriter(hostName, port, systemDb, null, userName, password, config, null);
+    }
+
+    @BeforeEach                                         
+    void dropTestDatabase() throws SQLException {
+        Statement drop = maintenanceDbWriter.getConnection().createStatement();
+        drop.executeQuery(String.format("DROP DATABASE IF EXISTS %s", dbName));
+    }
+
+    @Test
+    public void testCreateNewDatabase() throws SQLException {
+        ClickHouseCreateDatabase act = new ClickHouseCreateDatabase();
+        ClickHouseConnection conn = dbWriter.getConnection();
+        try {
+            act.createNewDatabase(conn, dbName);
+        } catch(SQLException se) {
+            //System.out.println(se.getMessage());
+            Assert.assertTrue(false);
+        }
+        Statement stmt = dbWriter.getConnection().createStatement();
+        String query = String.format("SELECT name FROM system.databases WHERE name = '%s'", dbName);
+        ResultSet rs = stmt.executeQuery(query);
+        Assert.assertTrue(rs.next());
+    }
+}