I would like to confirm the cost of a projection query. According 
to https://cloud.google.com/appengine/pricing the cost of a project query 
is 1 read operation while a a normal query getting the whole entity is 1 
read + 1 read per entity retrieved. 

If I have entities in this structure:

MyEntity
-ID
-Name
-Birthday

If I select do a projection query to get retrieve the ID and Name of 
everyone who's birthday is greater than a some date lets say Jan 1st 2000. 
If there are 100 entities which match does the return only count as 1 read 
to get all 100 entities back? If this is the case then say I also want to 
retrieve the birthday property, but don't wan't to select all the 
properties to avoid a query which gets the whole entity then why not then 
add a dummy property that has no use to the entities so then you can still 
select all the properties I need (ID,Name, and Birthday) and still only use 
1 read operation. 

If I did a query to select all the properties of a user who's birthday is 
greater than a some date lets say Jan 1st 2000. If there are 100 entities 
which match does the return will costs be 1 + 100 read operations? 

Cheers

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  • [google-appengine] C... Susan Lin

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