Vacuum SQLite database on server stop

Closes #132

src/main/java/de/epiceric/shopchest/ShopChest.java

@@ -209,6 +209,10 @@ public class ShopChest extends JavaPlugin {
                 debug("Removed shop (#" + shop.getID() + ")");
             }
 
+            if (database instanceof SQLite) {
+                ((SQLite) database).vacuum(false);
+            }
+
             database.disconnect();
         }
 

src/main/java/de/epiceric/shopchest/sql/Database.java

@@ -537,14 +537,14 @@ public abstract class Database {
     }
 
     /**
-     * Closes a {@link PreparedStatement} and a {@link ResultSet}
-     * @param ps {@link PreparedStatement} to close
+     * Closes a {@link Statement} and a {@link ResultSet}
+     * @param s {@link Statement} to close
      * @param rs {@link ResultSet} to close
      */
-    private void close(PreparedStatement ps, ResultSet rs) {
+    void close(Statement s, ResultSet rs) {
         try {
-            if (ps != null)
-                ps.close();
+            if (s != null)
+                s.close();
             if (rs != null)
                 rs.close();
         } catch (SQLException ex) {

src/main/java/de/epiceric/shopchest/sql/SQLite.java

@@ -1,12 +1,15 @@
 package de.epiceric.shopchest.sql;
 
 import de.epiceric.shopchest.ShopChest;
+import org.bukkit.scheduler.BukkitRunnable;
 
 import java.io.File;
 import java.io.IOException;
 import java.sql.Connection;
 import java.sql.DriverManager;
+import java.sql.PreparedStatement;
 import java.sql.SQLException;
+import java.sql.Statement;
 
 public class SQLite extends Database {
 
@@ -46,4 +49,36 @@ public class SQLite extends Database {
 
         return null;
     }
+
+    /**
+     * Vacuums the database to reduce file size
+     * @param async Whether the call should be executed asynchronously
+     */
+    public void vacuum(boolean async) {
+        BukkitRunnable runnable = new BukkitRunnable() {
+            @Override
+            public void run() {
+                Statement s = null;
+
+                try {
+                    s = connection.createStatement();
+                    s.executeUpdate("VACUUM");
+
+                    plugin.debug("Vacuumed SQLite database");
+                } catch (final SQLException ex) {
+                    plugin.getLogger().severe("Failed to access database");
+                    plugin.debug("Failed to vacuum database");
+                    plugin.debug(ex);
+                } finally {
+                    close(s, null);
+                }
+            }
+        };
+
+        if (async) {
+            runnable.runTaskAsynchronously(plugin);
+        } else {
+            runnable.run();
+        }
+    }
 }