Thanks to all of you for providing valuable suggestions!
I have solved the issue but in different way. As grouping binary data with text data could slowdown performance, I removed binary column(and entity) from aggregate and post that I checked if there is any binary data for any record, and only then I fetched binary data in a new aggregate. It is working fine and faster also.
The only thing I could not figure out is why aggregate was showing error in test mode perhaps it was able to fetch all data. To verify it, I copied executed SQL query and tried with Advance SQL widget, Here I get same data without any error.