Force database checkpoints on 'Clean-up' and 'Scan' actions

This will only affect the (embedded/legacy) HSQLDB driver. Even though
cff97ea9 should prevent the db log from getting uncontrollably large,
the 'Clean-up database' and 'Scan' actions will additionally force a
checkpoint to ensure this happens on big operations.

airsonic-main/src/main/java/org/airsonic/player/controller/MusicFolderSettingsController.java

@@ -96,6 +96,7 @@ public class MusicFolderSettingsController {
         artistDao.expunge();
         albumDao.expunge();
         mediaFileDao.expunge();
+        mediaFileDao.checkpoint();
     }
 
     private List<MusicFolderSettingsCommand.MusicFolderInfo> wrap(List<MusicFolder> musicFolders) {

airsonic-main/src/main/java/org/airsonic/player/dao/AbstractDao.java

@@ -189,4 +189,6 @@ public class AbstractDao {
         this.daoHelper = daoHelper;
     }
 
+    public boolean checkpoint() { return daoHelper.checkpoint(); }
+
 }

airsonic-main/src/main/java/org/airsonic/player/dao/DaoHelper.java

@@ -46,4 +46,14 @@ public interface DaoHelper {
     NamedParameterJdbcTemplate getNamedParameterJdbcTemplate();
 
     DataSource getDataSource();
+
+    /**
+     * Tries to perform a checkpoint against the database, if supported
+     *
+     * Database checkpoints will make sure that the database is written on the disk
+     * and optimize on-disk storage.
+     *
+     * @return true if the checkpoint succeeded
+     */
+    public boolean checkpoint();
 }

airsonic-main/src/main/java/org/airsonic/player/dao/GenericDaoHelper.java

@@ -1,12 +1,20 @@
 package org.airsonic.player.dao;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
+import org.springframework.jdbc.datasource.DataSourceUtils;
 
 import javax.sql.DataSource;
 
+import java.sql.Connection;
+import java.sql.DatabaseMetaData;
+
 public class GenericDaoHelper implements DaoHelper {
 
+    private static final Logger LOG = LoggerFactory.getLogger(GenericDaoHelper.class);
+
     final JdbcTemplate jdbcTemplate;
 
     final NamedParameterJdbcTemplate namedParameterJdbcTemplate;
@@ -35,4 +43,35 @@ public class GenericDaoHelper implements DaoHelper {
     public DataSource getDataSource() {
         return dataSource;
     }
+
+    @Override
+    public boolean checkpoint() {
+
+        try {
+            Connection conn = DataSourceUtils.getConnection(getJdbcTemplate().getDataSource());
+            DatabaseMetaData meta = conn.getMetaData();
+            String productName = meta.getDatabaseProductName();
+            int productVersion = meta.getDatabaseMajorVersion();
+
+            // HSQLDB (at least version 1) does not handle automatic checkpoints very well by default.
+            // This makes sure the temporary log is actually written to more persistent storage.
+            if (productName.equals("HSQL Database Engine") && (productVersion == 1 || productVersion == 2)) {
+                LOG.info("Performing database checkpoint");
+                getJdbcTemplate().execute("CHECKPOINT DEFRAG");
+                return true;
+            } else {
+                LOG.debug("Database checkpoint not implemented for '" + productName + "'");
+                return false;
+            }
+        }
+
+        // Since this method is a best-effort operation, we don't want to show
+        // a message if the checkpoint failed ; just assume the operation is
+        // unsupported.
+        catch(java.sql.SQLException e) {
+            LOG.debug("An exception occurred during database checkpoint: " + e.toString());
+        }
+
+        return false;
+    }
 }

airsonic-main/src/main/java/org/airsonic/player/service/MediaScannerService.java

@@ -156,6 +156,7 @@ public class MediaScannerService {
             public void run() {
                 doScanLibrary();
                 playlistService.importPlaylists();
+                mediaFileDao.checkpoint();
             }
         };