Q3C, Quad Tree Cube -- The new Sky-indexing Concept for Huge Astronomical Catalogues and its Realization for Main Astronomical Queries (Cone Search and Xmatch) in Open Source Database PostgreSQL

In this paper we present Q3C (Quad Tree Cube), a new sky indexing scheme and its implementation for the open source database PostgreSQL. We have implemented our sky-partitioning scheme as a loadable module for PostgreSQL and developed a very simple SQL interface for main astronomical queries: cone search, various spatial searches on the sphere and cross-matches of catalogues. The performance is very high and allows to work easily with the largest existing catalogues (USNO-A/B, 2MASS, SDSS). We propose PostgreSQL and our sky-indexing scheme as open source solution for any VO-services dealing with huge catalogues.