X-Git-Url: https://git.notmuchmail.org/git?p=notmuch;a=blobdiff_plain;f=lib%2Fmessage.cc;h=415eac1b9862033f7cf05f9f49d08eaf440b70de;hp=67875065f5c93f01edbad2387172d3767be59364;hb=604d1e0977c2ede365f87492d6b9bf9a83c3e1d3;hpb=d9f61c26a1344b123c1812392bc39c32634a099a

diff --git a/lib/message.cc b/lib/message.cc
index 67875065..415eac1b 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -39,6 +39,12 @@ struct visible _notmuch_message {
     notmuch_message_file_t *message_file;
     notmuch_message_list_t *replies;
     unsigned long flags;
+    /* For flags that are initialized on-demand, lazy_flags indicates
+     * if each flag has been initialized. */
+    unsigned long lazy_flags;
+
+    /* Message document modified since last sync */
+    notmuch_bool_t modified;
 
     Xapian::Document doc;
     Xapian::termcount termpos;
@@ -99,6 +105,7 @@ _notmuch_message_create_for_document (const void *talloc_owner,
 
     message->frozen = 0;
     message->flags = 0;
+    message->lazy_flags = 0;
 
     /* Each of these will be lazily created as needed. */
     message->message_id = NULL;
@@ -192,15 +199,17 @@ _notmuch_message_create (const void *talloc_owner,
  *
  *     There is already a document with message ID 'message_id' in the
  *     database. The returned message can be used to query/modify the
- *     document.
+ *     document. The message may be a ghost message.
+ *
  *   NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND:
  *
  *     No document with 'message_id' exists in the database. The
  *     returned message contains a newly created document (not yet
  *     added to the database) and a document ID that is known not to
- *     exist in the database. The caller can modify the message, and a
- *     call to _notmuch_message_sync will add * the document to the
- *     database.
+ *     exist in the database.  This message is "blank"; that is, it
+ *     contains only a message ID and no other metadata. The caller
+ *     can modify the message, and a call to _notmuch_message_sync
+ *     will add the document to the database.
  *
  * If an error occurs, this function will return NULL and *status
  * will be set as appropriate. (The status pointer argument must
@@ -224,6 +233,10 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
     else if (*status_ret)
 	return NULL;
 
+    /* If the message ID is too long, substitute its sha1 instead. */
+    if (strlen (message_id) > NOTMUCH_MESSAGE_ID_MAX)
+	message_id = _notmuch_message_id_compressed (message, message_id);
+
     term = talloc_asprintf (NULL, "%s%s",
 			    _find_prefix ("id"), message_id);
     if (term == NULL) {
@@ -242,7 +255,7 @@ _notmuch_message_create_for_message_id (notmuch_database_t *notmuch,
 
 	doc_id = _notmuch_database_generate_doc_id (notmuch);
     } catch (const Xapian::Error &error) {
-	fprintf (stderr, "A Xapian exception occurred creating message: %s\n",
+	_notmuch_database_log(_notmuch_message_database (message), "A Xapian exception occurred creating message: %s\n",
 		 error.get_msg().c_str());
 	notmuch->exception_reported = TRUE;
 	*status_ret = NOTMUCH_PRIVATE_STATUS_XAPIAN_EXCEPTION;
@@ -266,18 +279,18 @@ _notmuch_message_get_term (notmuch_message_t *message,
 			   const char *prefix)
 {
     int prefix_len = strlen (prefix);
-    const char *term = NULL;
     char *value;
 
     i.skip_to (prefix);
 
-    if (i != end)
-	term = (*i).c_str ();
+    if (i == end)
+	return NULL;
 
-    if (!term || strncmp (term, prefix, prefix_len))
+    const std::string &term = *i;
+    if (strncmp (term.c_str(), prefix, prefix_len))
 	return NULL;
 
-    value = talloc_strdup (message, term + prefix_len);
+    value = talloc_strdup (message, term.c_str() + prefix_len);
 
 #if DEBUG_DATABASE_SANITY
     i++;
@@ -299,6 +312,7 @@ _notmuch_message_ensure_metadata (notmuch_message_t *message)
     const char *thread_prefix = _find_prefix ("thread"),
 	*tag_prefix = _find_prefix ("tag"),
 	*id_prefix = _find_prefix ("id"),
+	*type_prefix = _find_prefix ("type"),
 	*filename_prefix = _find_prefix ("file-direntry"),
 	*replyto_prefix = _find_prefix ("replyto");
 
@@ -331,10 +345,25 @@ _notmuch_message_ensure_metadata (notmuch_message_t *message)
 	message->message_id =
 	    _notmuch_message_get_term (message, i, end, id_prefix);
 
+    /* Get document type */
+    assert (strcmp (id_prefix, type_prefix) < 0);
+    if (! NOTMUCH_TEST_BIT (message->lazy_flags, NOTMUCH_MESSAGE_FLAG_GHOST)) {
+	i.skip_to (type_prefix);
+	/* "T" is the prefix "type" fields.  See
+	 * BOOLEAN_PREFIX_INTERNAL. */
+	if (*i == "Tmail")
+	    NOTMUCH_CLEAR_BIT (&message->flags, NOTMUCH_MESSAGE_FLAG_GHOST);
+	else if (*i == "Tghost")
+	    NOTMUCH_SET_BIT (&message->flags, NOTMUCH_MESSAGE_FLAG_GHOST);
+	else
+	    INTERNAL_ERROR ("Message without type term");
+	NOTMUCH_SET_BIT (&message->lazy_flags, NOTMUCH_MESSAGE_FLAG_GHOST);
+    }
+
     /* Get filename list.  Here we get only the terms.  We lazily
      * expand them to full file names when needed in
      * _notmuch_message_ensure_filename_list. */
-    assert (strcmp (id_prefix, filename_prefix) < 0);
+    assert (strcmp (type_prefix, filename_prefix) < 0);
     if (!message->filename_term_list && !message->filename_list)
 	message->filename_term_list =
 	    _notmuch_database_get_terms_with_prefix (message, i, end,
@@ -365,6 +394,11 @@ _notmuch_message_invalidate_metadata (notmuch_message_t *message,
 	message->tag_list = NULL;
     }
 
+    if (strcmp ("type", prefix_name) == 0) {
+	NOTMUCH_CLEAR_BIT (&message->flags, NOTMUCH_MESSAGE_FLAG_GHOST);
+	NOTMUCH_CLEAR_BIT (&message->lazy_flags, NOTMUCH_MESSAGE_FLAG_GHOST);
+    }
+
     if (strcmp ("file-direntry", prefix_name) == 0) {
 	talloc_free (message->filename_term_list);
 	talloc_free (message->filename_list);
@@ -406,32 +440,50 @@ _notmuch_message_ensure_message_file (notmuch_message_t *message)
     if (unlikely (filename == NULL))
 	return;
 
-    message->message_file = _notmuch_message_file_open_ctx (message, filename);
+    message->message_file = _notmuch_message_file_open_ctx (
+	_notmuch_message_database (message), message, filename);
 }
 
 const char *
 notmuch_message_get_header (notmuch_message_t *message, const char *header)
 {
-    std::string value;
+    Xapian::valueno slot = Xapian::BAD_VALUENO;
 
     /* Fetch header from the appropriate xapian value field if
      * available */
     if (strcasecmp (header, "from") == 0)
-	value = message->doc.get_value (NOTMUCH_VALUE_FROM);
+	slot = NOTMUCH_VALUE_FROM;
     else if (strcasecmp (header, "subject") == 0)
-	value = message->doc.get_value (NOTMUCH_VALUE_SUBJECT);
+	slot = NOTMUCH_VALUE_SUBJECT;
     else if (strcasecmp (header, "message-id") == 0)
-	value = message->doc.get_value (NOTMUCH_VALUE_MESSAGE_ID);
+	slot = NOTMUCH_VALUE_MESSAGE_ID;
 
-    if (!value.empty())
-	return talloc_strdup (message, value.c_str ());
+    if (slot != Xapian::BAD_VALUENO) {
+	try {
+	    std::string value = message->doc.get_value (slot);
+
+	    /* If we have NOTMUCH_FEATURE_FROM_SUBJECT_ID_VALUES, then
+	     * empty values indicate empty headers.  If we don't, then
+	     * it could just mean we didn't record the header. */
+	    if ((message->notmuch->features &
+		 NOTMUCH_FEATURE_FROM_SUBJECT_ID_VALUES) ||
+		! value.empty())
+		return talloc_strdup (message, value.c_str ());
+
+	} catch (Xapian::Error &error) {
+	    _notmuch_database_log(_notmuch_message_database (message), "A Xapian exception occurred when reading header: %s\n",
+		     error.get_msg().c_str());
+	    message->notmuch->exception_reported = TRUE;
+	    return NULL;
+	}
+    }
 
     /* Otherwise fall back to parsing the file */
     _notmuch_message_ensure_message_file (message);
     if (message->message_file == NULL)
 	return NULL;
 
-    return notmuch_message_file_get_header (message->message_file, header);
+    return _notmuch_message_file_get_header (message->message_file, header);
 }
 
 /* Return the message ID from the In-Reply-To header of 'message'.
@@ -462,9 +514,9 @@ notmuch_message_get_thread_id (notmuch_message_t *message)
 
 void
 _notmuch_message_add_reply (notmuch_message_t *message,
-			    notmuch_message_node_t *reply)
+			    notmuch_message_t *reply)
 {
-    _notmuch_message_list_append (message->replies, reply);
+    _notmuch_message_list_add_message (message->replies, reply);
 }
 
 notmuch_messages_t *
@@ -473,6 +525,155 @@ notmuch_message_get_replies (notmuch_message_t *message)
     return _notmuch_messages_create (message->replies);
 }
 
+static void
+_notmuch_message_remove_terms (notmuch_message_t *message, const char *prefix)
+{
+    Xapian::TermIterator i;
+    size_t prefix_len = strlen (prefix);
+
+    while (1) {
+	i = message->doc.termlist_begin ();
+	i.skip_to (prefix);
+
+	/* Terminate loop when no terms remain with desired prefix. */
+	if (i == message->doc.termlist_end () ||
+	    strncmp ((*i).c_str (), prefix, prefix_len))
+	    break;
+
+	try {
+	    message->doc.remove_term ((*i));
+	    message->modified = TRUE;
+	} catch (const Xapian::InvalidArgumentError) {
+	    /* Ignore failure to remove non-existent term. */
+	}
+    }
+}
+
+/* Return true if p points at "new" or "cur". */
+static bool is_maildir (const char *p)
+{
+    return strcmp (p, "cur") == 0 || strcmp (p, "new") == 0;
+}
+
+/* Add "folder:" term for directory. */
+static notmuch_status_t
+_notmuch_message_add_folder_terms (notmuch_message_t *message,
+				   const char *directory)
+{
+    char *folder, *last;
+
+    folder = talloc_strdup (NULL, directory);
+    if (! folder)
+	return NOTMUCH_STATUS_OUT_OF_MEMORY;
+
+    /*
+     * If the message file is in a leaf directory named "new" or
+     * "cur", presume maildir and index the parent directory. Thus a
+     * "folder:" prefix search matches messages in the specified
+     * maildir folder, i.e. in the specified directory and its "new"
+     * and "cur" subdirectories.
+     *
+     * Note that this means the "folder:" prefix can't be used for
+     * distinguishing between message files in "new" or "cur". The
+     * "path:" prefix needs to be used for that.
+     *
+     * Note the deliberate difference to _filename_is_in_maildir(). We
+     * don't want to index different things depending on the existence
+     * or non-existence of all maildir sibling directories "new",
+     * "cur", and "tmp". Doing so would be surprising, and difficult
+     * for the user to fix in case all subdirectories were not in
+     * place during indexing.
+     */
+    last = strrchr (folder, '/');
+    if (last) {
+	if (is_maildir (last + 1))
+	    *last = '\0';
+    } else if (is_maildir (folder)) {
+	*folder = '\0';
+    }
+
+    _notmuch_message_add_term (message, "folder", folder);
+
+    talloc_free (folder);
+
+    return NOTMUCH_STATUS_SUCCESS;
+}
+
+#define RECURSIVE_SUFFIX "/**"
+
+/* Add "path:" terms for directory. */
+static notmuch_status_t
+_notmuch_message_add_path_terms (notmuch_message_t *message,
+				 const char *directory)
+{
+    /* Add exact "path:" term. */
+    _notmuch_message_add_term (message, "path", directory);
+
+    if (strlen (directory)) {
+	char *path, *p;
+
+	path = talloc_asprintf (NULL, "%s%s", directory, RECURSIVE_SUFFIX);
+	if (! path)
+	    return NOTMUCH_STATUS_OUT_OF_MEMORY;
+
+	/* Add recursive "path:" terms for directory and all parents. */
+	for (p = path + strlen (path) - 1; p > path; p--) {
+	    if (*p == '/') {
+		strcpy (p, RECURSIVE_SUFFIX);
+		_notmuch_message_add_term (message, "path", path);
+	    }
+	}
+
+	talloc_free (path);
+    }
+
+    /* Recursive all-matching path:** for consistency. */
+    _notmuch_message_add_term (message, "path", "**");
+
+    return NOTMUCH_STATUS_SUCCESS;
+}
+
+/* Add directory based terms for all filenames of the message. */
+static notmuch_status_t
+_notmuch_message_add_directory_terms (void *ctx, notmuch_message_t *message)
+{
+    const char *direntry_prefix = _find_prefix ("file-direntry");
+    int direntry_prefix_len = strlen (direntry_prefix);
+    Xapian::TermIterator i = message->doc.termlist_begin ();
+    notmuch_status_t status = NOTMUCH_STATUS_SUCCESS;
+
+    for (i.skip_to (direntry_prefix); i != message->doc.termlist_end (); i++) {
+	unsigned int directory_id;
+	const char *direntry, *directory;
+	char *colon;
+	const std::string &term = *i;
+
+	/* Terminate loop at first term without desired prefix. */
+	if (strncmp (term.c_str (), direntry_prefix, direntry_prefix_len))
+	    break;
+
+	/* Indicate that there are filenames remaining. */
+	status = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
+
+	direntry = term.c_str ();
+	direntry += direntry_prefix_len;
+
+	directory_id = strtol (direntry, &colon, 10);
+
+	if (colon == NULL || *colon != ':')
+	    INTERNAL_ERROR ("malformed direntry");
+
+	directory = _notmuch_database_get_directory_path (ctx,
+							  message->notmuch,
+							  directory_id);
+
+	_notmuch_message_add_folder_terms (message, directory);
+	_notmuch_message_add_path_terms (message, directory);
+    }
+
+    return status;
+}
+
 /* Add an additional 'filename' for 'message'.
  *
  * This change will not be reflected in the database until the next
@@ -489,6 +690,10 @@ _notmuch_message_add_filename (notmuch_message_t *message,
     if (filename == NULL)
 	INTERNAL_ERROR ("Message filename cannot be NULL.");
 
+    if (! (message->notmuch->features & NOTMUCH_FEATURE_FILE_TERMS) ||
+	! (message->notmuch->features & NOTMUCH_FEATURE_BOOL_FOLDER))
+	return NOTMUCH_STATUS_UPGRADE_REQUIRED;
+
     relative = _notmuch_database_relative_path (message->notmuch, filename);
 
     status = _notmuch_database_split_path (local, relative, &directory, NULL);
@@ -504,8 +709,8 @@ _notmuch_message_add_filename (notmuch_message_t *message,
      * notmuch_directory_get_child_files() . */
     _notmuch_message_add_term (message, "file-direntry", direntry);
 
-    /* New terms allow user to search with folder: specification. */
-    _notmuch_message_gen_terms (message, "folder", directory);
+    _notmuch_message_add_folder_terms (message, directory);
+    _notmuch_message_add_path_terms (message, directory);
 
     talloc_free (local);
 
@@ -523,22 +728,19 @@ _notmuch_message_add_filename (notmuch_message_t *message,
  * Note: This function does not remove a document from the database,
  * even if the specified filename is the only filename for this
  * message. For that functionality, see
- * _notmuch_database_remove_message. */
+ * notmuch_database_remove_message. */
 notmuch_status_t
 _notmuch_message_remove_filename (notmuch_message_t *message,
 				  const char *filename)
 {
-    const char *direntry_prefix = _find_prefix ("file-direntry");
-    int direntry_prefix_len = strlen (direntry_prefix);
-    const char *folder_prefix = _find_prefix ("folder");
-    int folder_prefix_len = strlen (folder_prefix);
     void *local = talloc_new (message);
-    char *zfolder_prefix = talloc_asprintf(local, "Z%s", folder_prefix);
-    int zfolder_prefix_len = strlen (zfolder_prefix);
     char *direntry;
     notmuch_private_status_t private_status;
     notmuch_status_t status;
-    Xapian::TermIterator i, last;
+
+    if (! (message->notmuch->features & NOTMUCH_FEATURE_FILE_TERMS) ||
+	! (message->notmuch->features & NOTMUCH_FEATURE_BOOL_FOLDER))
+	return NOTMUCH_STATUS_UPGRADE_REQUIRED;
 
     status = _notmuch_database_filename_to_direntry (
 	local, message->notmuch, filename, NOTMUCH_FIND_LOOKUP, &direntry);
@@ -553,83 +755,36 @@ _notmuch_message_remove_filename (notmuch_message_t *message,
     if (status)
 	return status;
 
-    /* Re-synchronize "folder:" terms for this message. This requires:
-     *  1. removing all "folder:" terms
-     *  2. removing all "folder:" stemmed terms
-     *  3. adding back terms for all remaining filenames of the message. */
+    /* Re-synchronize "folder:" and "path:" terms for this message. */
 
-    /* 1. removing all "folder:" terms */
-    while (1) {
-	i = message->doc.termlist_begin ();
-	i.skip_to (folder_prefix);
+    /* Remove all "folder:" terms. */
+    _notmuch_message_remove_terms (message, _find_prefix ("folder"));
 
-	/* Terminate loop when no terms remain with desired prefix. */
-	if (i == message->doc.termlist_end () ||
-	    strncmp ((*i).c_str (), folder_prefix, folder_prefix_len))
-	{
-	    break;
-	}
+    /* Remove all "path:" terms. */
+    _notmuch_message_remove_terms (message, _find_prefix ("path"));
 
-	try {
-	    message->doc.remove_term ((*i));
-	} catch (const Xapian::InvalidArgumentError) {
-	    /* Ignore failure to remove non-existent term. */
-	}
-    }
+    /* Add back terms for all remaining filenames of the message. */
+    status = _notmuch_message_add_directory_terms (local, message);
 
-    /* 2. removing all "folder:" stemmed terms */
-    while (1) {
-	i = message->doc.termlist_begin ();
-	i.skip_to (zfolder_prefix);
-
-	/* Terminate loop when no terms remain with desired prefix. */
-	if (i == message->doc.termlist_end () ||
-	    strncmp ((*i).c_str (), zfolder_prefix, zfolder_prefix_len))
-	{
-	    break;
-	}
-
-	try {
-	    message->doc.remove_term ((*i));
-	} catch (const Xapian::InvalidArgumentError) {
-	    /* Ignore failure to remove non-existent term. */
-	}
-    }
-
-    /* 3. adding back terms for all remaining filenames of the message. */
-    i = message->doc.termlist_begin ();
-    i.skip_to (direntry_prefix);
-
-    for (; i != message->doc.termlist_end (); i++) {
-	unsigned int directory_id;
-	const char *direntry, *directory;
-	char *colon;
-
-	/* Terminate loop at first term without desired prefix. */
-	if (strncmp ((*i).c_str (), direntry_prefix, direntry_prefix_len))
-	    break;
-
-	/* Indicate that there are filenames remaining. */
-	status = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
-
-	direntry = (*i).c_str ();
-	direntry += direntry_prefix_len;
-
-	directory_id = strtol (direntry, &colon, 10);
+    talloc_free (local);
 
-	if (colon == NULL || *colon != ':')
-	    INTERNAL_ERROR ("malformed direntry");
+    return status;
+}
 
-	directory = _notmuch_database_get_directory_path (local,
-							  message->notmuch,
-							  directory_id);
-	if (strlen (directory))
-	    _notmuch_message_gen_terms (message, "folder", directory);
-    }
+/* Upgrade the "folder:" prefix from V1 to V2. */
+#define FOLDER_PREFIX_V1       "XFOLDER"
+#define ZFOLDER_PREFIX_V1      "Z" FOLDER_PREFIX_V1
+void
+_notmuch_message_upgrade_folder (notmuch_message_t *message)
+{
+    /* Remove all old "folder:" terms. */
+    _notmuch_message_remove_terms (message, FOLDER_PREFIX_V1);
 
-    talloc_free (local);
+    /* Remove all old "folder:" stemmed terms. */
+    _notmuch_message_remove_terms (message, ZFOLDER_PREFIX_V1);
 
-    return status;
+    /* Add new boolean "folder:" and "path:" terms. */
+    _notmuch_message_add_directory_terms (message, message);
 }
 
 char *
@@ -642,6 +797,7 @@ void
 _notmuch_message_clear_data (notmuch_message_t *message)
 {
     message->doc.set_data ("");
+    message->modified = TRUE;
 }
 
 static void
@@ -745,7 +901,11 @@ notmuch_bool_t
 notmuch_message_get_flag (notmuch_message_t *message,
 			  notmuch_message_flag_t flag)
 {
-    return message->flags & (1 << flag);
+    if (flag == NOTMUCH_MESSAGE_FLAG_GHOST &&
+	! NOTMUCH_TEST_BIT (message->lazy_flags, flag))
+	_notmuch_message_ensure_metadata (message);
+
+    return NOTMUCH_TEST_BIT (message->flags, flag);
 }
 
 void
@@ -753,9 +913,10 @@ notmuch_message_set_flag (notmuch_message_t *message,
 			  notmuch_message_flag_t flag, notmuch_bool_t enable)
 {
     if (enable)
-	message->flags |= (1 << flag);
+	NOTMUCH_SET_BIT (&message->flags, flag);
     else
-	message->flags &= ~(1 << flag);
+	NOTMUCH_CLEAR_BIT (&message->flags, flag);
+    NOTMUCH_SET_BIT (&message->lazy_flags, flag);
 }
 
 time_t
@@ -766,10 +927,15 @@ notmuch_message_get_date (notmuch_message_t *message)
     try {
 	value = message->doc.get_value (NOTMUCH_VALUE_TIMESTAMP);
     } catch (Xapian::Error &error) {
-	INTERNAL_ERROR ("Failed to read timestamp value from document.");
+	_notmuch_database_log(_notmuch_message_database (message), "A Xapian exception occurred when reading date: %s\n",
+		 error.get_msg().c_str());
+	message->notmuch->exception_reported = TRUE;
 	return 0;
     }
 
+    if (value.empty ())
+	/* sortable_unserialise is undefined on empty string */
+	return 0;
     return Xapian::sortable_unserialise (value);
 }
 
@@ -788,18 +954,20 @@ notmuch_message_get_tags (notmuch_message_t *message)
      * possible to modify the message tags (which talloc_unlink's the
      * current list from the message) while still iterating because
      * the iterator will keep the current list alive. */
-    talloc_reference (message, message->tag_list);
+    if (!talloc_reference (message, message->tag_list))
+	return NULL;
+
     return tags;
 }
 
 const char *
-notmuch_message_get_author (notmuch_message_t *message)
+_notmuch_message_get_author (notmuch_message_t *message)
 {
     return message->author;
 }
 
 void
-notmuch_message_set_author (notmuch_message_t *message,
+_notmuch_message_set_author (notmuch_message_t *message,
 			    const char *author)
 {
     if (message->author)
@@ -827,6 +995,17 @@ _notmuch_message_set_header_values (notmuch_message_t *message,
 			    Xapian::sortable_serialise (time_value));
     message->doc.add_value (NOTMUCH_VALUE_FROM, from);
     message->doc.add_value (NOTMUCH_VALUE_SUBJECT, subject);
+    message->modified = TRUE;
+}
+
+/* Upgrade a message to support NOTMUCH_FEATURE_LAST_MOD.  The caller
+ * must call _notmuch_message_sync. */
+void
+_notmuch_message_upgrade_last_mod (notmuch_message_t *message)
+{
+    /* _notmuch_message_sync will update the last modification
+     * revision; we just have to ask it to. */
+    message->modified = TRUE;
 }
 
 /* Synchronize changes made to message->doc out into the database. */
@@ -838,24 +1017,82 @@ _notmuch_message_sync (notmuch_message_t *message)
     if (message->notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY)
 	return;
 
+    if (! message->modified)
+	return;
+
+    /* Update the last modification of this message. */
+    if (message->notmuch->features & NOTMUCH_FEATURE_LAST_MOD)
+	/* sortable_serialise gives a reasonably compact encoding,
+	 * which directly translates to reduced IO when scanning the
+	 * value stream.  Since it's built for doubles, we only get 53
+	 * effective bits, but that's still enough for the database to
+	 * last a few centuries at 1 million revisions per second. */
+	message->doc.add_value (NOTMUCH_VALUE_LAST_MOD,
+				Xapian::sortable_serialise (
+				    _notmuch_database_new_revision (
+					message->notmuch)));
+
     db = static_cast <Xapian::WritableDatabase *> (message->notmuch->xapian_db);
     db->replace_document (message->doc_id, message->doc);
+    message->modified = FALSE;
 }
 
-/* Delete a message document from the database. */
+/* Delete a message document from the database, leaving a ghost
+ * message in its place */
 notmuch_status_t
 _notmuch_message_delete (notmuch_message_t *message)
 {
     notmuch_status_t status;
     Xapian::WritableDatabase *db;
+    const char *mid, *tid;
+    notmuch_message_t *ghost;
+    notmuch_private_status_t private_status;
+    notmuch_database_t *notmuch;
+
+    mid = notmuch_message_get_message_id (message);
+    tid = notmuch_message_get_thread_id (message);
+    notmuch = message->notmuch;
 
     status = _notmuch_database_ensure_writable (message->notmuch);
     if (status)
 	return status;
 
-    db = static_cast <Xapian::WritableDatabase *> (message->notmuch->xapian_db);
+    db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
     db->delete_document (message->doc_id);
-    return NOTMUCH_STATUS_SUCCESS;
+
+    /* and reintroduce a ghost in its place */
+    ghost = _notmuch_message_create_for_message_id (notmuch, mid, &private_status);
+    if (private_status == NOTMUCH_PRIVATE_STATUS_NO_DOCUMENT_FOUND) {
+	private_status = _notmuch_message_initialize_ghost (ghost, tid);
+	if (! private_status)
+	    _notmuch_message_sync (ghost);
+    } else if (private_status == NOTMUCH_PRIVATE_STATUS_SUCCESS) {
+	/* this is deeply weird, and we should not have gotten into
+	   this state.  is there a better error message to return
+	   here? */
+	return NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
+    }
+
+    notmuch_message_destroy (ghost);
+    return COERCE_STATUS (private_status, "Error converting to ghost message");
+}
+
+/* Transform a blank message into a ghost message.  The caller must
+ * _notmuch_message_sync the message. */
+notmuch_private_status_t
+_notmuch_message_initialize_ghost (notmuch_message_t *message,
+				   const char *thread_id)
+{
+    notmuch_private_status_t status;
+
+    status = _notmuch_message_add_term (message, "type", "ghost");
+    if (status)
+	return status;
+    status = _notmuch_message_add_term (message, "thread", thread_id);
+    if (status)
+	return status;
+
+    return NOTMUCH_PRIVATE_STATUS_SUCCESS;
 }
 
 /* Ensure that 'message' is not holding any file object open. Future
@@ -866,7 +1103,7 @@ void
 _notmuch_message_close (notmuch_message_t *message)
 {
     if (message->message_file) {
-	notmuch_message_file_close (message->message_file);
+	_notmuch_message_file_close (message->message_file);
 	message->message_file = NULL;
     }
 }
@@ -896,6 +1133,7 @@ _notmuch_message_add_term (notmuch_message_t *message,
 	return NOTMUCH_PRIVATE_STATUS_TERM_TOO_LONG;
 
     message->doc.add_term (term, 0);
+    message->modified = TRUE;
 
     talloc_free (term);
 
@@ -918,16 +1156,23 @@ _notmuch_message_gen_terms (notmuch_message_t *message,
 	return NOTMUCH_PRIVATE_STATUS_NULL_POINTER;
 
     term_gen->set_document (message->doc);
-    term_gen->set_termpos (message->termpos);
 
     if (prefix_name) {
 	const char *prefix = _find_prefix (prefix_name);
 
+	term_gen->set_termpos (message->termpos);
 	term_gen->index_text (text, 1, prefix);
-	message->termpos = term_gen->get_termpos ();
+	/* Create a gap between this an the next terms so they don't
+	 * appear to be a phrase. */
+	message->termpos = term_gen->get_termpos () + 100;
+
+	_notmuch_message_invalidate_metadata (message, prefix_name);
     }
 
+    term_gen->set_termpos (message->termpos);
     term_gen->index_text (text);
+    /* Create a term gap, as above. */
+    message->termpos = term_gen->get_termpos () + 100;
 
     return NOTMUCH_PRIVATE_STATUS_SUCCESS;
 }
@@ -957,8 +1202,9 @@ _notmuch_message_remove_term (notmuch_message_t *message,
 
     try {
 	message->doc.remove_term (term);
+	message->modified = TRUE;
     } catch (const Xapian::InvalidArgumentError) {
-	/* We'll let the philosopher's try to wrestle with the
+	/* We'll let the philosophers try to wrestle with the
 	 * question of whether failing to remove that which was not
 	 * there in the first place is failure. For us, we'll silently
 	 * consider it all good. */
@@ -1027,13 +1273,54 @@ notmuch_message_remove_tag (notmuch_message_t *message, const char *tag)
     return NOTMUCH_STATUS_SUCCESS;
 }
 
+/* Is the given filename within a maildir directory?
+ *
+ * Specifically, is the final directory component of 'filename' either
+ * "cur" or "new". If so, return a pointer to that final directory
+ * component within 'filename'. If not, return NULL.
+ *
+ * A non-NULL return value is guaranteed to be a valid string pointer
+ * pointing to the characters "new/" or "cur/", (but not
+ * NUL-terminated).
+ */
+static const char *
+_filename_is_in_maildir (const char *filename)
+{
+    const char *slash, *dir = NULL;
+
+    /* Find the last '/' separating directory from filename. */
+    slash = strrchr (filename, '/');
+    if (slash == NULL)
+	return NULL;
+
+    /* Jump back 4 characters to where the previous '/' will be if the
+     * directory is named "cur" or "new". */
+    if (slash - filename < 4)
+	return NULL;
+
+    slash -= 4;
+
+    if (*slash != '/')
+	return NULL;
+
+    dir = slash + 1;
+
+    if (STRNCMP_LITERAL (dir, "cur/") == 0 ||
+	STRNCMP_LITERAL (dir, "new/") == 0)
+    {
+	return dir;
+    }
+
+    return NULL;
+}
+
 notmuch_status_t
 notmuch_message_maildir_flags_to_tags (notmuch_message_t *message)
 {
     const char *flags;
     notmuch_status_t status;
     notmuch_filenames_t *filenames;
-    const char *filename;
+    const char *filename, *dir;
     char *combined_flags = talloc_strdup (message, "");
     unsigned i;
     int seen_maildir_info = 0;
@@ -1043,15 +1330,25 @@ notmuch_message_maildir_flags_to_tags (notmuch_message_t *message)
 	 notmuch_filenames_move_to_next (filenames))
     {
 	filename = notmuch_filenames_get (filenames);
+	dir = _filename_is_in_maildir (filename);
 
-	flags = strstr (filename, ":2,");
-	if (! flags)
+	if (! dir)
 	    continue;
 
-	seen_maildir_info = 1;
-	flags += 3;
-
-	combined_flags = talloc_strdup_append (combined_flags, flags);
+	flags = strstr (filename, ":2,");
+	if (flags) {
+	    seen_maildir_info = 1;
+	    flags += 3;
+	    combined_flags = talloc_strdup_append (combined_flags, flags);
+	} else if (STRNCMP_LITERAL (dir, "new/") == 0) {
+	    /* Messages are delivered to new/ with no "info" part, but
+	     * they effectively have default maildir flags.  According
+	     * to the spec, we should ignore the info part for
+	     * messages in new/, but some MUAs (mutt) can set maildir
+	     * flags on messages in new/, so we're liberal in what we
+	     * accept. */
+	    seen_maildir_info = 1;
+	}
     }
 
     /* If none of the filenames have any maildir info field (not even
@@ -1083,47 +1380,6 @@ notmuch_message_maildir_flags_to_tags (notmuch_message_t *message)
     return status;
 }
 
-/* Is the given filename within a maildir directory?
- *
- * Specifically, is the final directory component of 'filename' either
- * "cur" or "new". If so, return a pointer to that final directory
- * component within 'filename'. If not, return NULL.
- *
- * A non-NULL return value is guaranteed to be a valid string pointer
- * pointing to the characters "new/" or "cur/", (but not
- * NUL-terminated).
- */
-static const char *
-_filename_is_in_maildir (const char *filename)
-{
-    const char *slash, *dir = NULL;
-
-    /* Find the last '/' separating directory from filename. */
-    slash = strrchr (filename, '/');
-    if (slash == NULL)
-	return NULL;
-
-    /* Jump back 4 characters to where the previous '/' will be if the
-     * directory is named "cur" or "new". */
-    if (slash - filename < 4)
-	return NULL;
-
-    slash -= 4;
-
-    if (*slash != '/')
-	return NULL;
-
-    dir = slash + 1;
-
-    if (STRNCMP_LITERAL (dir, "cur/") == 0 ||
-	STRNCMP_LITERAL (dir, "new/") == 0)
-    {
-	return dir;
-    }
-
-    return NULL;
-}
-
 /* From the set of tags on 'message' and the flag2tag table, compute a
  * set of maildir-flag actions to be taken, (flags that should be
  * either set or cleared).
@@ -1183,7 +1439,9 @@ _get_maildir_flag_actions (notmuch_message_t *message,
  * compute the new maildir filename.
  *
  * If the existing filename is in the directory "new", the new
- * filename will be in the directory "cur".
+ * filename will be in the directory "cur", except for the case when
+ * no flags are changed and the existing filename does not contain
+ * maildir info (starting with ",2:").
  *
  * After a sequence of ":2," in the filename, any subsequent
  * single-character flags will be added or removed according to the
@@ -1206,6 +1464,7 @@ _new_maildir_filename (void *ctx,
     char *filename_new, *dir;
     char flag_map[128];
     int flags_in_map = 0;
+    notmuch_bool_t flags_changed = FALSE;
     unsigned int i;
     char *s;
 
@@ -1246,6 +1505,7 @@ _new_maildir_filename (void *ctx,
 	if (flag_map[flag] == 0) {
 	    flag_map[flag] = 1;
 	    flags_in_map++;
+	    flags_changed = TRUE;
 	}
     }
 
@@ -1254,9 +1514,16 @@ _new_maildir_filename (void *ctx,
 	if (flag_map[flag]) {
 	    flag_map[flag] = 0;
 	    flags_in_map--;
+	    flags_changed = TRUE;
 	}
     }
 
+    /* Messages in new/ without maildir info can be kept in new/ if no
+     * flags have changed. */
+    dir = (char *) _filename_is_in_maildir (filename);
+    if (dir && STRNCMP_LITERAL (dir, "new/") == 0 && !*info && !flags_changed)
+	return talloc_strdup (ctx, filename);
+
     filename_new = (char *) talloc_size (ctx,
 					 info - filename +
 					 strlen (":2,") + flags_in_map + 1);
@@ -1345,7 +1612,7 @@ notmuch_message_tags_to_maildir_flags (notmuch_message_t *message)
     talloc_free (to_set);
     talloc_free (to_clear);
 
-    return NOTMUCH_STATUS_SUCCESS;
+    return status;
 }
 
 notmuch_status_t
@@ -1418,3 +1685,9 @@ notmuch_message_destroy (notmuch_message_t *message)
 {
     talloc_free (message);
 }
+
+notmuch_database_t *
+_notmuch_message_database (notmuch_message_t *message)
+{
+    return message->notmuch;
+}