notmuch restore: Don't waste time with messages with unchanged tags.

It's a simple optimization to look at a message and check that the
existing tags are actually different than the tags we are setting
before we do anything.

For my mail store this takes a "notmuch restore" that does nothing
from about 10 minutes down to 1 minute, so there's a significant
speedup here.

diff --git a/notmuch-restore.c b/notmuch-restore.c
index 1b9598dcee5ec1dd42c075d1255781333ddc5de5..53ce2548dc71ddf9755f497aa9a184542ade66ec 100644 (file)
--- a/notmuch-restore.c
+++ b/notmuch-restore.c
@@ -63,9 +63,11 @@ notmuch_restore_command (unused (void *ctx), int argc, char *argv[])
 
     while ((line_len = getline (&line, &line_size, input)) != -1) {
        regmatch_t match[3];
-       char *message_id, *tags, *tag, *next;
-       notmuch_message_t *message;
+       char *message_id, *file_tags, *tag, *next;
+       notmuch_message_t *message = NULL;
        notmuch_status_t status;
+       notmuch_tags_t *db_tags;
+       char *db_tags_str;
 
        chomp_newline (line);
 
@@ -79,8 +81,8 @@ notmuch_restore_command (unused (void *ctx), int argc, char *argv[])
 
        message_id = xstrndup (line + match[1].rm_so,
                               match[1].rm_eo - match[1].rm_so);
-       tags = xstrndup (line + match[2].rm_so,
-                        match[2].rm_eo - match[2].rm_so);
+       file_tags = xstrndup (line + match[2].rm_so,
+                             match[2].rm_eo - match[2].rm_so);
 
        message = notmuch_database_find_message (notmuch, message_id);
        if (message == NULL) {
@@ -89,11 +91,30 @@ notmuch_restore_command (unused (void *ctx), int argc, char *argv[])
            goto NEXT_LINE;
        }
 
-       notmuch_message_freeze (message);
+       db_tags_str = NULL;
+       for (db_tags = notmuch_message_get_tags (message);
+            notmuch_tags_has_more (db_tags);
+            notmuch_tags_advance (db_tags))
+       {
+           const char *tag = notmuch_tags_get (db_tags);
+
+           if (db_tags_str)
+               db_tags_str = talloc_asprintf_append (db_tags_str, " %s", tag);
+           else
+               db_tags_str = talloc_strdup (message, tag);
+       }
+
+       if (((file_tags == NULL || *file_tags == '\0') &&
+            (db_tags_str == NULL || *db_tags_str == '\0')) ||
+           (file_tags && db_tags_str && strcmp (file_tags, db_tags_str) == 0))
+       {
+           goto NEXT_LINE;
+       }
 
+       notmuch_message_freeze (message);
        notmuch_message_remove_all_tags (message);
 
-       next = tags;
+       next = file_tags;
        while (next) {
            tag = strsep (&next, " ");
            if (*tag == '\0')
@@ -109,10 +130,13 @@ notmuch_restore_command (unused (void *ctx), int argc, char *argv[])
        }
 
        notmuch_message_thaw (message);
-       notmuch_message_destroy (message);
+
       NEXT_LINE:
+       if (message)
+           notmuch_message_destroy (message);
+       message = NULL;
        free (message_id);
-       free (tags);
+       free (file_tags);
     }
 
     regfree (&regex);