Using the indexing and sampling APIs to realize progressive features

Hi,

I have some questions regarding the indexing and sampling API.

My aim is to implement a variant of progressive indexing as seen in this
paper (link
<chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http:/www.vldb.org/pvld
b/vol12/p2366-holanda.pdf> ). To summarize,

I want to implement a variant of online aggregation, where an aggregate
query (Like Sum, Average, etc.) is answered in real time, where the result
becomes more and more accurate as Tuples are consumed.

I thought that I could maybe use a custom sampling routine to consume table
samples until I have seen the whole table with no duplicate tuples.

Meanwhile, with every consumed sample and returned partial answer, I want to
add the tuples consumed to a progressively evolving index.

This would mean that I would have to be able to uniquely identify each row
to be able to add them to the growing index, right? Since OID is deprecated
/ phased out, I am still unsure of how to solve this.

Does this sound reasonable or is there an obvious flaw in my thinking?

I would also be thankful if there is any material beyond the Postgres
documentation which helps me to start out modifying the source to realize
something like this.

Regards

Michael H.