// ConditionalPut sets the value for a specified key only if
// the expected value matches. If not, the return value contains
// the actual value.
func (r *Range) ConditionalPut(args *proto.ConditionalPutRequest, reply *proto.ConditionalPutResponse) {
// Handle check for non-existence of key.
val, err := r.engine.Get(args.Key)
if err != nil {
reply.SetGoError(err)
return
}
if args.ExpValue.Bytes == nil && val != nil {
reply.SetGoError(util.Errorf("key %q already exists", args.Key))
return
} else if args.ExpValue.Bytes != nil {
// Handle check for existence when there is no key.
if val == nil {
reply.SetGoError(util.Errorf("key %q does not exist", args.Key))
return
} else if !bytes.Equal(args.ExpValue.Bytes, val) {
// TODO(Jiang-Ming): provide the correct timestamp once switch to use MVCC
reply.ActualValue = &proto.Value{Bytes: val}
reply.SetGoError(util.Errorf("key %q does not match existing", args.Key))
return
}
}
reply.SetGoError(r.internalPut(args.Key, args.Value))
}
// ConditionalPut sets the value for a specified key only if
// the expected value matches. If not, the return value contains
// the actual value.
func (r *Range) ConditionalPut(args *proto.ConditionalPutRequest, reply *proto.ConditionalPutResponse) {
val, err := r.mvcc.ConditionalPut(args.Key, args.Timestamp, args.Value, args.ExpValue, args.Txn)
if err == nil {
r.updateGossipConfigs(args.Key)
}
reply.ActualValue = val
reply.SetGoError(err)
}