Limit subject threading to 24 hours

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

@@ -424,8 +424,9 @@ public interface DaoMessage {
     @Query("SELECT * FROM message" +
             " WHERE account = :account" +
             " AND sender = :sender" +
-            " AND subject = :subject")
-    List<EntityMessage> getMessagesBySubject(long account, String sender, String subject);
+            " AND subject = :subject" +
+            " AND received >= :since")
+    List<EntityMessage> getMessagesBySubject(long account, String sender, String subject, long since);
 
     @Query("SELECT message.* FROM message" +
             " LEFT JOIN message AS base ON base.id = :id" +
@@ -647,8 +648,10 @@ public interface DaoMessage {
     int updateMessage(EntityMessage message);
 
     @Query("UPDATE message SET thread = :thread" +
-            " WHERE account = :account AND thread = :old AND NOT (:old IS :thread)")
-    int updateMessageThread(long account, String old, String thread);
+            " WHERE account = :account" +
+            " AND thread = :old AND NOT (:old IS :thread)" +
+            " AND (:since IS NULL OR received >= :since)")
+    int updateMessageThread(long account, String old, String thread, Long since);
 
     @Query("UPDATE message SET uid = :uid WHERE id = :id AND NOT (uid IS :uid)")
     int setMessageUid(long id, Long uid);

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

@@ -83,6 +83,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
     private SwitchCompat swSyncKept;
     private SwitchCompat swGmailThread;
     private SwitchCompat swSubjectThreading;
+    private TextView tvSubjectThreading;
     private SwitchCompat swSyncFolders;
     private SwitchCompat swSyncFoldersPoll;
     private SwitchCompat swSyncSharedFolders;
@@ -152,6 +153,7 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
         swSyncKept = view.findViewById(R.id.swSyncKept);
         swGmailThread = view.findViewById(R.id.swGmailThread);
         swSubjectThreading = view.findViewById(R.id.swSubjectThreading);
+        tvSubjectThreading = view.findViewById(R.id.tvSubjectThreading);
         swSyncFolders = view.findViewById(R.id.swSyncFolders);
         swSyncFoldersPoll = view.findViewById(R.id.swSyncFoldersPoll);
         swSyncSharedFolders = view.findViewById(R.id.swSyncSharedFolders);
@@ -422,6 +424,8 @@ public class FragmentOptionsSynchronize extends FragmentBase implements SharedPr
         // Initialize
         FragmentDialogTheme.setBackground(getContext(), view, false);
 
+        tvSubjectThreading.setText(getString(R.string.title_advanced_subject_threading_hint, MessageHelper.MAX_SUBJECT_AGE));
+
         DB db = DB.getInstance(getContext());
         db.account().liveSynchronizingAccounts().observe(getViewLifecycleOwner(), new Observer<List<EntityAccount>>() {
             @Override

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

@@ -129,6 +129,7 @@ public class MessageHelper {
     static final int SMALL_MESSAGE_SIZE = 192 * 1024; // bytes
     static final int DEFAULT_DOWNLOAD_SIZE = 4 * 1024 * 1024; // bytes
     static final String HEADER_CORRELATION_ID = "X-Correlation-ID";
+    static final int MAX_SUBJECT_AGE = 48; // hours
 
     private static final int MAX_HEADER_LENGTH = 998;
     private static final int MAX_MESSAGE_SIZE = 10 * 1024 * 1024; // bytes
@@ -1324,31 +1325,31 @@ public class MessageHelper {
         for (EntityMessage message : before)
             if (!thread.equals(message.thread)) {
                 Log.w("Updating before thread from " + message.thread + " to " + thread);
-                db.message().updateMessageThread(message.account, message.thread, thread);
+                db.message().updateMessageThread(message.account, message.thread, thread, null);
             }
 
         List<EntityMessage> after = db.message().getMessagesByInReplyTo(account, msgid);
         for (EntityMessage message : after)
             if (!thread.equals(message.thread)) {
                 Log.w("Updating after thread from " + message.thread + " to " + thread);
-                db.message().updateMessageThread(message.account, message.thread, thread);
+                db.message().updateMessageThread(message.account, message.thread, thread, null);
             }
 
         boolean subject_threading = prefs.getBoolean("subject_threading", false);
         if (subject_threading) {
             String sender = getSortKey(getFrom());
             String subject = getSubject();
+            long since = new Date().getTime() - MAX_SUBJECT_AGE * 3600 * 1000L;
             if (!TextUtils.isEmpty(sender) && !TextUtils.isEmpty(subject)) {
-                List<EntityMessage> subjects = db.message().getMessagesBySubject(account, sender, subject);
+                List<EntityMessage> subjects = db.message().getMessagesBySubject(account, sender, subject, since);
                 for (EntityMessage message : subjects)
                     if (!thread.equals(message.thread)) {
                         Log.w("Updating subject thread from " + message.thread + " to " + thread);
-                        db.message().updateMessageThread(message.account, message.thread, thread);
+                        db.message().updateMessageThread(message.account, message.thread, thread, since);
                     }
             }
         }
 
-
         return thread;
     }
 

app/src/main/res/layout/fragment_options_synchronize.xml

@@ -589,6 +589,19 @@
                     app:layout_constraintTop_toBottomOf="@id/tvGmailThreadHint"
                     app:switchPadding="12dp" />
 
+                <eu.faircode.email.FixedTextView
+                    android:id="@+id/tvSubjectThreading"
+                    android:layout_width="0dp"
+                    android:layout_height="wrap_content"
+                    android:layout_marginStart="12dp"
+                    android:layout_marginEnd="48dp"
+                    android:text="@string/title_advanced_subject_threading_hint"
+                    android:textAppearance="@style/TextAppearance.AppCompat.Small"
+                    android:textStyle="italic"
+                    app:layout_constraintEnd_toEndOf="parent"
+                    app:layout_constraintStart_toStartOf="parent"
+                    app:layout_constraintTop_toBottomOf="@id/swSubjectThreading" />
+
                 <androidx.appcompat.widget.SwitchCompat
                     android:id="@+id/swSyncFolders"
                     android:layout_width="0dp"
@@ -598,7 +611,7 @@
                     android:text="@string/title_advanced_sync_folders"
                     app:layout_constraintEnd_toEndOf="parent"
                     app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toBottomOf="@id/swSubjectThreading"
+                    app:layout_constraintTop_toBottomOf="@id/tvSubjectThreading"
                     app:switchPadding="12dp" />
 
                 <eu.faircode.email.FixedTextView

app/src/main/res/values/strings.xml

@@ -716,6 +716,7 @@
     <string name="title_advanced_deleted_unseen">When disabled, unread messages are kept on the device forever</string>
     <string name="title_advanced_sync_kept_hint">This will transfer extra data and consume extra battery power, especially if a lot of messages are stored on the device</string>
     <string name="title_advanced_gmail_thread_hint">This only applies to newly received messages and can break existing groups</string>
+    <string name="title_advanced_subject_threading_hint">Only messages received in the last %1$d hours</string>
     <string name="title_advanced_sync_folders_hint">Disabling this will reduce data and battery usage somewhat, but will disable updating the list of folders too</string>
     <string name="title_advanced_poll_folders_hint">Periodically synchronize the folder list in addition to after connecting to an account</string>
     <string name="title_advanced_check_authentication_hint">This will check the results of DKIM, SPF and DMARC authentication as performed by the email server</string>