struct OP_QUERY {
MsgHeader header; // standard message header
int32 flags; // bit vector of query options
cstring fullCollectionName ; // "dbname.collectionname"
int32 numberToSkip; // number of documents to skip
int32 numberToReturn; // number of documents to return in the first batch
document query; // query object.
[ document returnFieldsSelector; ] // Selector indicating the fields to return
}