Names of the fields in the table that should be read. If
empty, all fields will be read. If the specified field is a
nested field, all the sub-fields in the field will be
selected. The output field order is unrelated to the order
of fields in selected_fields.
SQL text filtering statement, similar to a WHERE clause in a
query. Aggregates are not supported.
Examples: "int_field > 5" "date_field = CAST('2014-9-27' as
DATE)" "nullable_field is not NULL" "st_equals(geo_field,
st_geofromtext("POINT(2, 2)"))" "numeric_field BETWEEN 1.0
Restricted to a maximum length for 1 MB.