Function value_to_bson_for_query 

pub fn value_to_bson_for_query(
    schema: &ClassSchema,
    field: &str,
    value: &ParseValue,
) -> Result<Bson, ParseError>

Lower a value for use in a query filter on field.

Differs from the create path in one way that matters: a declared Pointer field stores "Class$id", so a query for a pointer has to compare against that string rather than against the __type envelope. Getting this wrong makes every pointer query silently return nothing.