Clustering the large VizieR catalogues, the CoCat experience

VizieR is a database containing about 4000 astronomical catalogues with homogeneous descriptions. The major part of the catalogues is stored in a relational database but the large catalogues containing over 10 millions rows are stored as compressed binary files and have dedicated query programs for very fast access by celestial coordinates. The CoCat (Co-processor Catalogue) project main goal is to parallelize the VizieR large catalogue treatments (data extraction, cross-matching) for reducing the response time.