||All of the Sky: HEALPix Density Maps of Gaia-scale Datasets from the Database to the Desktop
||521, Astronomical Data Analysis Software and Systems XXVI
||Taylor, M. B.; Mantelet, G.; Demleitner, M.
||The Gaia Archive provides access to observations of around
a billion sky sources.
The primary access to this archive is via TAP services such as GACS
which allow execution of SQL-like queries against a large remote database
returning a result set of manageable size for client-side use.
Such services are generally used for extracting relatively small source
lists according to potentially complex selection criteria.
But they can also be used to obtain statistical information
about all, or a large fraction of, the observed sources
by building histogram-like results.
We examine here the practicalities of producing and consuming
all-sky HEALPix weighted density maps in this way for Gaia and
other large datasets.
We present some modest requirements on TAP/RDBMS services
to enable such queries, and discuss visualisation and serialization
options for the results including some new capabilities in recent
versions of TOPCAT.