Can I Scan table for highest Range key value for each item?

Question

Problem: I want to get all items with highest range key.

Example:

id	version
test1	3
test1	4
test2	2
test2	3

I expect from query:

id	version
test1	4
test2	3

My table is like:

id string -> hash key 
version number -> range key

I'm using guregu and I'm scanning all results to get highest version number.

var results []map[string]interface{}
err := d.table.Scan().All(&results)

What is the best practice to find items with the highest sort key ?

Answer 1

If you changed your data model slightly where you have a record such as V0 in the below image, you could index sparsely on the latest value allowing you to easily get the the latest version for all items in an efficient manner.

The alternative is to Scan then Query which is extremely inefficient. So if it's a frequent lookup pattern, an index is best.