slow index lookups on large mailboxes

[Deniss]

hello here,

after upgrade of cyrus from 2.3 to 2.4 I noticed some slowdown on few 
huge mailboxes doing multiple FETCH UID queries. I briefly checked a 
codebase of new cyrus and found out that to find any required record in 
index the new code loops through all records and output matched data.
for example:
     for (msgno = 1; msgno <= state->exists; msgno++) {
         im = &state->map[msgno-1];
         checkval = usinguid ? im->record.uid : msgno;
         if (!seqset_ismember(seq, checkval))
             continue;
         r = index_fetchreply(state, msgno, fetchargs);
         if (r) break;
         fetched = 1;
     }

This approach brings constant time of index query for any numbers of 
requested records. But for large indexes and single record requested 
this algorithm is clearly ineffective.

is there plans to tune index lookups in future ?

best,
  Deniss