When checking whether the core tables have been alredy created it is
best to use package_table.exists(), as are_tables_created reflects the
tables, causing conflicts with other extensions.
This allows ckanext-harvest and ckanext-spatial to be used together on
ckan 1.8 onwards.
The spatial_query plugin now automatically checks for the existance of an
'spatial' extra when creating, updating or deleting a package and syncs its
value (in GeoJSON format) with the geometry column of the package_extent
table. The extension now uses GeoAlchemy, that makes performing spatial
operation extremely easy. The geometry field has been updated to support
multiple geometry types (Polygons, Points, MultiPolygons...) and the default
srid has been set as WGS 84 lat/lon (EPSG:4326).
amercader
David Read