Always keep and synchronize flagged messages

app/src/main/java/eu/faircode/email/DB.java

@@ -46,7 +46,7 @@ import io.requery.android.database.sqlite.RequerySQLiteOpenHelperFactory;
 // https://developer.android.com/topic/libraries/architecture/room.html
 
 @Database(
-        version = 12,
+        version = 13,
         entities = {
                 EntityIdentity.class,
                 EntityAccount.class,
@@ -220,6 +220,13 @@ public abstract class DB extends RoomDatabase {
                         db.execSQL("CREATE INDEX `index_operation_message` ON `operation` (`message`)");
                     }
                 })
+                .addMigrations(new Migration(12, 13) {
+                    @Override
+                    public void migrate(SupportSQLiteDatabase db) {
+                        Log.i(Helper.TAG, "DB migration from version " + startVersion + " to " + endVersion);
+                        db.execSQL("CREATE  INDEX `index_message_ui_flagged` ON `message` (`ui_flagged`)");
+                    }
+                })
                 .build();
     }
 

app/src/main/java/eu/faircode/email/DaoMessage.java

@@ -300,20 +300,27 @@ public interface DaoMessage {
     @Query("DELETE FROM message WHERE id = :id")
     int deleteMessage(long id);
 
-    @Query("DELETE FROM message WHERE folder = :folder AND uid = :uid")
+    @Query("DELETE FROM message" +
+            " WHERE folder = :folder" +
+            " AND uid = :uid")
     int deleteMessage(long folder, long uid);
 
-    @Query("DELETE FROM message WHERE folder = :folder AND NOT uid IS NULL")
+    @Query("DELETE FROM message" +
+            " WHERE folder = :folder" +
+            " AND NOT uid IS NULL")
     int deleteLocalMessages(long folder);
 
-    @Query("DELETE FROM message WHERE folder = :folder AND seen")
+    @Query("DELETE FROM message" +
+            " WHERE folder = :folder" +
+            " AND seen")
     int deleteSeenMessages(long folder);
 
     @Query("DELETE FROM message" +
             " WHERE folder = :folder" +
             " AND received < :received" +
             " AND NOT uid IS NULL" +
-            " AND (NOT ui_browsed OR :browsed)")
+            " AND (NOT ui_browsed OR :browsed)" +
+            " AND NOT ui_flagged")
     int deleteMessagesBefore(long folder, long received, boolean browsed);
 
     @Query("DELETE FROM message WHERE ui_found")

app/src/main/java/eu/faircode/email/EntityMessage.java

@@ -74,6 +74,7 @@ import static androidx.room.ForeignKey.SET_NULL;
                 @Index(value = {"thread"}),
                 @Index(value = {"received"}),
                 @Index(value = {"ui_seen"}),
+                @Index(value = {"ui_flagged"}),
                 @Index(value = {"ui_hide"}),
                 @Index(value = {"ui_found"}),
                 @Index(value = {"ui_ignored"}),

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -114,6 +114,8 @@ import javax.mail.event.StoreListener;
 import javax.mail.internet.InternetAddress;
 import javax.mail.internet.MimeMessage;
 import javax.mail.search.ComparisonTerm;
+import javax.mail.search.FlagTerm;
+import javax.mail.search.OrTerm;
 import javax.mail.search.ReceivedDateTerm;
 import javax.net.ssl.SSLException;
 
@@ -1881,7 +1883,12 @@ public class ServiceSynchronize extends LifecycleService {
 
             // Reduce list of local uids
             long search = SystemClock.elapsedRealtime();
-            Message[] imessages = ifolder.search(new ReceivedDateTerm(ComparisonTerm.GE, new Date(sync_time)));
+            Message[] imessages = ifolder.search(
+                    new OrTerm(
+                            new ReceivedDateTerm(ComparisonTerm.GE, new Date(sync_time)),
+                            new FlagTerm(new Flags(Flags.Flag.FLAGGED), true)
+                    )
+            );
             Log.i(Helper.TAG, folder.name + " remote count=" + imessages.length +
                     " search=" + (SystemClock.elapsedRealtime() - search) + " ms");