lib-index: Fix repetitive "missing middle file seq" error.

If a view keeps being synced with MAIL_INDEX_VIEW_SYNC_FLAG_NOEXPUNGES,
every sync regenerated the missing log files and logged this error.
This could have resulted in lots of errors being logged about it, as
well as unnecessary CPU usage.

The view syncing was always syncing from the last "expunge log position",
even when expunges weren't being synced. The new behavior is to do that
only when expunges are synced, but otherwise use the "head log position"
to sync only the new changes since the last view sync.

The error is now logged once when the log is first noticed being lost.
Another error is logged when pending expunges are synced.

diff --git a/src/lib-index/mail-index-view-sync.c b/src/lib-index/mail-index-view-sync.c
index 1aa52fac7668e8b0c510e3fe40ec3353819882b8..ba92f07e639f2b1f95273e197a5538555a751d32 100644 (file)
--- a/src/lib-index/mail-index-view-sync.c
+++ b/src/lib-index/mail-index-view-sync.c
@@ -52,10 +52,20 @@ view_sync_set_log_view_range(struct mail_index_view *view, bool sync_expunges,
 
        *partial_sync_r = FALSE;
 
-       start_seq = view->log_file_expunge_seq;
-       start_offset = view->log_file_expunge_offset;
-       end_seq = hdr->log_file_seq;
-       end_offset = hdr->log_file_head_offset;
+       if (sync_expunges) {
+               /* Sync everything after the last expunge syncing position.
+                  We'll just skip over the non-expunge transaction records
+                  that have already been synced previously. */
+               start_seq = view->log_file_expunge_seq;
+               start_offset = view->log_file_expunge_offset;
+       } else {
+               /* Sync only new changes since the last view sync. */
+               start_seq = view->log_file_head_seq;
+               start_offset = view->log_file_head_offset;
+       }
+       /* Sync the view up to the (already refreshed) index map. */
+        end_seq = hdr->log_file_seq;
+        end_offset = hdr->log_file_head_offset;
 
        if (end_seq < view->log_file_head_seq ||
            (end_seq == view->log_file_head_seq &&
@@ -485,12 +495,18 @@ view_sync_get_log_lost_changes(struct mail_index_view_sync_ctx *ctx,
        old_map->hdr.log_file_tail_offset = 0;
 
        if ((ctx->flags & MAIL_INDEX_VIEW_SYNC_FLAG_NOEXPUNGES) != 0) {
+               /* Expunges aren't wanted to be synced. Remember if we skipped
+                  over any expunges. If yes, we must not update
+                  log_file_expunge_seq/offset at the end of the view sync
+                  so that a later sync can finish the expunges. */
                array_clear(&ctx->expunges);
                ctx->skipped_expunges = *expunge_count_r > 0;
-       } else {
-               view->log_file_head_seq = new_map->hdr.log_file_seq;
-               view->log_file_head_offset = new_map->hdr.log_file_head_offset;
        }
+       /* After the view sync is finished, update
+          log_file_head_seq/offset, since we've synced everything
+          (except maybe the expunges) up to this point. */
+       view->log_file_head_seq = new_map->hdr.log_file_seq;
+       view->log_file_head_offset = new_map->hdr.log_file_head_offset;
        return 0;
 }
 
@@ -595,8 +611,16 @@ mail_index_view_sync_begin(struct mail_index_view *view,
                        return ctx;
                }
                have_expunges = expunge_count > 0;
-       } else {
+       } else if (view->log_file_expunge_seq == view->log_file_head_seq &&
+                  view->log_file_expunge_offset == view->log_file_head_offset) {
+               /* Previous syncs haven't left any pending expunges. See if
+                  this sync will. */
                have_expunges = view_sync_have_expunges(view);
+       } else {
+               /* Expunges weren't synced in the previous sync either.
+                  We already know there are missing expunges. */
+               ctx->skipped_expunges = TRUE;
+               have_expunges = TRUE;
        }
 
        ctx->finish_min_msg_count = reset ? 0 :