Hide Zen home . ... Index . ... Do we really need them for database indexing ? ... We need simple numbering scheme, so that for any given point we could easily calculate the number of "pixel", this is what HealPix provides and lacks HTM. ... During Rtree queries the number of index blocks read is several times greater than during Q3C queries. ... But in Q3C scheme, as we showed before, the circle is segmented, so we extract from the database only a few percents more data than occur in the circle. ...