GAE Datastore read operation pricing

Question

Suppose if we do

select * from Products where category = "electronics"

versus

select name, price from Products where category = "electronics"

What impact will it have on datastore pricing ?

From Google Cloud Platform doc it is written: Projection queries that do not use the distinct on clause. This type of query is counted as a single entity read for the query itself. The individual results are counted as small operations.

Answer 1

There are two things to trade off with respect to pricing. The projection query will need a composite index which will cause an increase in storage costs, but the queries will be cheaper by O(num results * read price).