Hi Andrey, I'll try to answer your questions inline. First off, I'm using these docs as reference:
http://code.google.com/appengine/docs/java/javadoc/com/google/appengine/api/datastore/KeyFactory.Builder.html http://code.google.com/appengine/docs/java/datastore/transactions.html > It works. But there are couple things which bother me. First at all, > there is some extra job here. I actually don't need instance of parent > class (MyList). > I have the parent key. Theoretically speaking, it is the only thing > needed to maintain parent child relationship. MyList class may have > more fields I don't need at all. So, I'd like to avoid reading them to > memory. > You can do this with KeyFactory.Builder. Build a Key using the parent and child Keys, then query using this Key. You can also use an ancestor query to find multiple child items. > Second concern is about line > > myList.items.add(item); > > what if MyList already has million of items? How efficient is add > operation in this case. > It's O(Linear) in memory, but as far as saving goes, adding a new child element is a single row write + index writes. It's not dependent on the number of items you already have. We have a series of articles describing here: http://code.google.com/appengine/articles/datastore/overview.html > Any thoughts? Is it possible to store child object using parent key > only? > Yep. Use KeyFactory.Builder to build and set a Key. > > Thank you, > Andrey > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to > [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-appengine-java%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > > -- Ikai Lan Developer Relations, Google App Engine Twitter: http://twitter.com/ikai Delicious: http://delicious.com/ikailan ---------------- Google App Engine links: Blog: http://googleappengine.blogspot.com Twitter: http://twitter.com/app_engine Reddit: http://www.reddit.com/r/appengine -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
