It is possible to have virtual scrolling with client side paging but it is not possible to limit the scrolling to the current page. The pageSize determines the size of the data chunk that will be loaded.
If you want to limit the amount of records that will be loaded just pass them as data to the DataSource. For example if you have total 1000 records but want to make a finite scrolling to 500 records with 50 pageSize, you have to set the pageSize of the dataSource to 50 and the data of the dataSource to the first 500 records of the 1000 records data set.
If you want to change the amount of the data you may use the data method of the DataSource to replace the current 500 records with others.
I would not recommend overriding the render method. The pageSize should not be exactly the same amount as the currently visible rows. In order to get a smooth scrolling you will need a pageSize bigger than the amount of records that the users sees.
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