Paginginfo

We routinely retrieve small subsets of data into a paging grid that ultimately comes from a much larger dataset. If you use a with() wrapped around your rule to retrieve data, and display your datasubset values somewhere while testing, this behavior becomes more clear.

For example, your total dataset contains 500 items, but you only want to display (and keep in memory) 100 at a time. You set your paging info values to: startIndex:1, batchSize:100.

You display your grid, if you display your datasubset in a paragraph field, you'll see three important values:
datasubset.startIndex:1, datasubset.batchSize:100, datasubset.totalCount: 500,

If you page your grid to the next one hundred and examine your values, you'll see:
datasubset.startIndex:101, datasubset.batchSize:100, datasubset.totalCount:500

In other words, it will retrieve values from 101 - 200 by taking the startIndex as the starting point and the batchSize as the amount to retrieve in this batch

It is imperative that you use the value and saveInto of your pagingGrid to update the values used to retrieve the data from the database (or other datasource)

From a performance perspective, if you are using a database backend and are retrieving these values from a table, consider the performance possibilities of Indexes, Partitions and even periodically materialized views to speed retrieval