lib: Add support for nested atomic sections.

[notmuch] / lib / database.cc

diff --git a/lib/database.cc b/lib/database.cc
index 9c2f4ecdc58ff2bcb6de93eba16b8ddc3dfd0b00..92c3c4e0a7f03088f9a8337233fc35056605e9fc 100644 (file)
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -273,6 +273,8 @@ notmuch_status_to_string (notmuch_status_t status)
        return "Tag value is too long (exceeds NOTMUCH_TAG_MAX)";
     case NOTMUCH_STATUS_UNBALANCED_FREEZE_THAW:
        return "Unbalanced number of calls to notmuch_message_freeze/thaw";
+    case NOTMUCH_STATUS_UNBALANCED_ATOMIC:
+       return "Unbalanced number of calls to notmuch_database_begin_atomic/end_atomic";
     default:
     case NOTMUCH_STATUS_LAST_STATUS:
        return "Unknown error status value";
@@ -611,6 +613,7 @@ notmuch_database_open (const char *path,
 
     notmuch->needs_upgrade = FALSE;
     notmuch->mode = mode;
+    notmuch->atomic_nesting = 0;
     try {
        string last_thread_id;
 
@@ -974,6 +977,61 @@ notmuch_database_upgrade (notmuch_database_t *notmuch,
     return NOTMUCH_STATUS_SUCCESS;
 }
 
+notmuch_status_t
+notmuch_database_begin_atomic (notmuch_database_t *notmuch)
+{
+    if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY ||
+       notmuch->atomic_nesting > 0)
+       goto DONE;
+
+    try {
+       (static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db))->begin_transaction (false);
+    } catch (const Xapian::Error &error) {
+       fprintf (stderr, "A Xapian exception occurred beginning transaction: %s.\n",
+                error.get_msg().c_str());
+       notmuch->exception_reported = TRUE;
+       return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+    }
+
+DONE:
+    notmuch->atomic_nesting++;
+    return NOTMUCH_STATUS_SUCCESS;
+}
+
+notmuch_status_t
+notmuch_database_end_atomic (notmuch_database_t *notmuch)
+{
+    Xapian::WritableDatabase *db;
+
+    if (notmuch->atomic_nesting == 0)
+       return NOTMUCH_STATUS_UNBALANCED_ATOMIC;
+
+    if (notmuch->mode == NOTMUCH_DATABASE_MODE_READ_ONLY ||
+       notmuch->atomic_nesting > 1)
+       goto DONE;
+
+    db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
+    try {
+       db->commit_transaction ();
+
+       /* This is a hack for testing.  Xapian never flushes on a
+        * non-flushed commit, even if the flush threshold is 1.
+        * However, we rely on flushing to test atomicity. */
+       const char *thresh = getenv ("XAPIAN_FLUSH_THRESHOLD");
+       if (thresh && atoi (thresh) == 1)
+           db->commit ();
+    } catch (const Xapian::Error &error) {
+       fprintf (stderr, "A Xapian exception occurred committing transaction: %s.\n",
+                error.get_msg().c_str());
+       notmuch->exception_reported = TRUE;
+       return NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+    }
+
+DONE:
+    notmuch->atomic_nesting--;
+    return NOTMUCH_STATUS_SUCCESS;
+}
+
 /* We allow the user to use arbitrarily long paths for directories. But
  * we have a term-length limit. So if we exceed that, we'll use the
  * SHA-1 of the path for the database term.