def _build_geojson_select(statement):
"""
See usages below.
"""
# this is basically a translation of the postgis ST_AsGeoJSON example into sqlalchemy/geoalchemy2
return func.json_build_object(
"type",
"FeatureCollection",
"features",
func.json_agg(func.ST_AsGeoJSON(statement.subquery(), maxdecimaldigits=5).cast(JSON)),
)
def json_agg(query):
return session.session.query(func.json_agg(literal_column("row"))) \
.select_from(Alias(query.subquery(), "row"))
def json_agg_core(selectable):
return select([func.json_agg(literal_column("row"))]) \
.select_from(selectable.alias("row"))