Bump! In my opinion, the 2nd one performs better but use more storage. Because the first one fan out (n + m) copies whereas the second one fans out (n * m) copies.
This is just MY THEORY. Please correct me if I am wrong. Thanks a lot, Max On 1月28日, 上午1時06分, Raphael André Bauer <[email protected]> wrote: > Hi everybody, > > Suppose you have to entities. Entity1 has one list, Entity2 has two lists: > > Entity1 > List<String> tags_and_timestamps > > Entity2 > List<String> tags > List<String> timestamps > > (I hope the peseudocode is ok - the questions is a general datastore > question and not dependent on JPA/JDO or low-level api). > > Then I want to merge join my entities based on two properties: a > timestamp and on a tag. > > Entity1 is a stupid entity simply storing everyhting in one list. > So I merge join on one list: > tags_and_timestamps == timestamp AND tags_and_timestamps == tag > > Entity2 is separates both values, so I merge join on: > timestamps == timestamp AND tags == tag > > The question is now: What is more efficient on the GAE datastore? > Separating the values into different lists or storing everything in > one list? > > Thanks a lot, > > Raphael -- 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.
