lei up: faster non-thread, single-source incremental query

When using isearch (that is v1/v2 inbox relying on extindex
for search), there's actually no guarantee that IMAP UIDs
are in the correct order with regard to Xapian docids.

Thus we must iterate through every UID(num) to see if it's
suitable to display in a saved search.  The old grep filter
(before commit a6fe84489127) was not effective since it
didn't account for the mset->items correspondence.

Fortunately, this bug merely manifests in reduced performance
as of a6fe84489127.  Prior to that, it could cause incorrect
keywords and labels to be applied.

Unfortunately, this behavior is hard-to-test so no test case
is included.

Followup-to: a6fe84489127 (lei up: fix missing -t/--threads matches w/ saved search)

0 files changed, 0 insertions, 0 deletions