Question

I need to optimize the read/write count for a POST request that I’m using.

Some info about the request:

• The user sends a JSON array of ~100 items
• The servlet needs to check if any of the received items is newer then its counterpart in the datastore using a single long attribute
• I’m using JDO

what i currently do is (pseudo code):

 foreach(item : json.items) {
     storedItem = persistenceManager.getObjectById(item.key);
     if(item.long > storedItem.long) {
         // Update storedItem
     }
 }

Which obviously results in ~100 read requests per request.

What is the best way to reduce the read count for this logic? Using JDO Query? I read that using “IN”-Queries simply results in multiple queries executed after another, so I don’t think that would help me 🙁

There also is PersistenceManager.getObjectsById(Collection). Does that help in any way? Can’t find any documentation of how many requests this will issue.

Answer 1

I think you can use below call to do a batch get:

Query q = pm.newQuery("select from " + Content.class.getName() + " where contentKey == :contentKeys");   

Something like above query would return all objects you need.
And you can handle all the rest from here.