Each user U, has 0 or more children data entities corresponding to days D. Each day D has 0 or more children data entities of types X, Y and Z.
Is it better to associate items X, Y and Z with an entity of type D by: 1. creating a collection each of X, Y and Z data entities inside entity D (e.g., private List<Y> childrenOfTypeY;), or by 2. storing X, Y and Z by generating their Key values such that it contains the parent entity D's key (e.g., Key k = new KeyFactory.Builder(D.class.getSimpleName(), "BlahBlahBlah").addChild(X.class.getSimpleName(), "YadaYadaYada").getKey();). My primary concern is which type of data design will be better resource/time consumption-wise (i.e., which way is "lighter"). AFAIK, method 1 gives me automatic consistency, method 2 gives me flexibility. In method 1, when I fetch an entity of type D, are all children entities of types X, Y & Z fetched in one go, or lazily (w/o programmatic intervention) on an as-required basis? In method 2 fetching the children is of course up to me. Other characteristics of my application: * As far as writing is concerned, it is more likely that individual children of an entity of type D will be written to. * As far as reading from the datastore is concerned, it is more likely that all children of 1 or more entities of type D will need to be fetched to satisfy a single request. * Once an entity of type D is created, it and its children are unlikely to be deleted, though entities of type X, Y and Z (for a given entity D) may be individually modified. * Data consistency is obviously of concern, but since data deletion is infrequent, app-managed consistency shouldn't be too hard. Plus, a cleanup Task can delete orphan X, Y, Z objects (should that happen). If it matters, I am using Java. If the above explanation is too opaque :-) or I have posted to the wrong group, please let me know. Thanks! -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appeng...@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
