if you use group in same dbgrid (devexpress) is necessary to use maxfetchrows, is good idea

you can limit rows simply by SQL statement like:
select bla bla from table rows 1000

My suggestion for this feature is that it would limit the total number of rows that would be retrieved. A value of -1 would mean all rows. But say a value of 10000 when there are 5M rows would retireve only a max of 10000. And that 10000 would hopefully be something that the server understands, as it would be much more efficient to do a "select * from items" and have the server prepare a resultset of just 10000 rows vs. having it prepare a resultset of 5M and then have a Uni component limit that to the 10000. I know that there will be cases in which a server might not support this, in which case Uni should emulate. This approach is similar to a feature in AnyDAC and I think it is quite useful.

Our DataSets already have the FetchRows property which provides this functionality (If FetchRows = 1000, Next will retrieve additional 1000 records when 1000th record is reached). Also you can use FetchRows=1000 and UniDirectional=True if you want keep in the memory last 1000 record only. Please tell us if you mean some other functionality for “max count”. MaxFetchRows should set the absolute limit.

This should also allow the client to execute a next to retrieve the subsequent number of records restricted by the max count. So max count = 1000 execute retrieves an additional 1000 etc