anchor.diff:                  let ba = bson.toBinaryArray newDoc
                   if ba.Length > 16*1024*1024 then raise (MongoCode(10329, "document more than 16MB"))
                   ba
  +
  +            let fn_getIndexes() = indexes
   
               let fn_insert newDoc =
                   let ba = to_bson newDoc
  
positive.code:                     | Some ndxu ->
                          getStmtForIndex ndxu
                      | None ->
                          let collTable = getTableNameForCollection db coll
                          conn.prepare(sprintf "SELECT bson FROM \"%s\"" collTable)
  
  
negative.code:         update:BsonValue->unit
          delete:BsonValue->bool
          getSelect:(plan.q option)->reader
          getIndexes:unit->index_info[]
          commit:unit->unit
          rollback:unit->unit
      }
  